Current Human Evolution [Archive]

View Full Version : Current Human Evolution

Another God

Jul30-03, 10:35 AM

LURCH

Jul30-03, 03:34 PM

That is a tuff one. The best I can come up with is that the human race has reached a point where we are able to alter our environment to suit ourselves, rather than altering ourselves to suit our environment. You could try saying that once we began builing homes, furniture, machines etc. to fit us perfectly the way we are, pressure to eveolve ceased because any alteration from our current configuration would be a dissadvantage.

It makes sense if you don't look at it too closely.

Phobos

Jul30-03, 04:55 PM

Originally posted by LURCH
It makes sense if you don't look at it too closely.

Agree. When you do examine it closely, it falls apart. [;)]

A.G. - I think one would need to seriously redefine/limit the terms of evolution in order to say it's no longer happening.

iansmith

Jul30-03, 05:17 PM

I think evolution is still taking place but the enviromental pressure has change, mostly, in developed country. We still face disease and microbial attack. For example, some people are showing resistance to AIDS. If this resistance has a genetic basis then AIDS resistance migth be a new starting point for evolution.

Another theoritical example is that people are becoming excessevly obese. There migth be biological and social pressure for obsese people to be selected against. Therefore people with faster metabolism migth become the fitter individual. People with faster metabolism migth have a better overall health and migth be more fertile.

With human, social pressure and technology have an equal voice with mother nature when it comes to evolution wheres with animals technology (a wood stick to get ants is technology for a chimp) and social pressure have less influence.

Evolution also migth take a long time therefore we migth not see the results.

[Edit: spelling]

Another God

Jul30-03, 07:47 PM

Originally posted by Phobos
Agree. When you do examine it closely, it falls apart. [;)]
Thats exactly the problem. I keep trying to think up angles on which a negative side can argue this...but every superficially convincing argument is crap upon inspection. And for this debate so far we ahve only decided which topic we want to do, and the teams haven't been sorted yet, so I don't know whether I will get to be on the affirmative or the negative...I'll just have to fight my way over to the affirmative and hope the other guys haven't thought about it yet, and so don't realise just how impossible the negative is to argue.

Perhaps I could argue that very very soon we will be able to engineer ourselves, and it is at this point that evolution will stop. We will deny the natural world control over our genes etc and start controlling the movement of all genes. Thus halting genetic drift and with it 'Evolution'.

selfAdjoint

Jul30-03, 09:09 PM

Whatever our circumstances may be in the modern world, variation in our genes keeps happening, and our environment is still selecting some who leave more descendents than others. So the mechanisms of evolution are still under way, with what ultimate result we cannot say.

Many social thinkers worry that the more prosperous people get, the fewer children thay tend to have, on the average. This means that over the long run the prosperous (sometimes characterized as "intelligent") are evolutionary losers. Their descendents will be nothinmg much compared to the descendents of the still fertile poor.

I think this is worrying too soon. We don't know what the future of the human race will be. Perhaps there will be another bottleneck and only a few individuals will be the ancestors of all the future human race. Nobody can say. But evolution is surely wending its slow way through our species as we post.

megashawn

Jul30-03, 10:32 PM

I mean, even if we have the ability to control our enviroments, this allows for less stressfull living, which would allow for more time for education, hobbies, etc. I'd say even if we've quit physically evolving, we could probably never reach a point where we quit mentally evolving. (which, I imagine is still physical evolution)

I mean, the less we have to be out working or hunting, warring or what ever, the more time we have to do, well, whatever we want.

I'd say not only are we still evolving, but we are slowly gaining control of our own evolution.

mythos

Jul31-03, 01:31 PM

If you think about it, the only way any species could stop evolving is either

1) they stop reproducing

or

2) each member of the species produce an equal number of surviving offspring

O Great One

Jul31-03, 08:41 PM

or

3) they only reproduce after their own "kind"

LURCH

Jul31-03, 11:48 PM

Originally posted by Another God
Thats exactly the problem. I keep trying to think up angles on which a negative side can argue this...but every superficially convincing argument is crap upon inspection. And for this debate so far we ahve only decided which topic we want to do, and the teams haven't been sorted yet, so I don't know whether I will get to be on the affirmative or the negative...I'll just have to fight my way over to the affirmative and hope the other guys haven't thought about it yet, and so don't realise just how impossible the negative is to argue.

Perhaps I could argue that very very soon we will be able to engineer ourselves, and it is at this point that evolution will stop. We will deny the natural world control over our genes etc and start controlling the movement of all genes. Thus halting genetic drift and with it 'Evolution'.

Perhaps you could use the difficulty of measuring evolution as a wedge. Evolutionary biologists sometimes say (said, actully; you don't hear this much nowadays) that the process of human evolution is happening so gradually that it can't be measured.

Modern science is all about the measuring. We can measure angles down to a billionth of a billionth of a degree, make measurements of time and space to such fine subtlety that we can not distinguish between the two (but we can still measure them). Yet with all this precission, we cannot measure how the race has evolved since the beginning of recorded medical history. Cross-breeding and genetic drift, sure; but no evolutionary trend. Since in science no measurement = no validation, you might get some points with that one.

(does anybody swallow that load of garbage?!)

Adam

Aug1-03, 12:33 AM

Another God

Is evolution currently happening to humans? This is easy to answer. Take a look at your parents and grandparents. Are you an exact duplicate of any of them? I doubt it. Most likely you will find that you have certain traits of each.

I would, however, suggest that we are mostly beyond one facet of evolution, that being natural selection. The "purpose" of natural selection is to create a version of any given species which is safe from the common threats of its environment. We are safe from such. There aren't many things more dangerous than humans. Perhaps it is still in action, weeding out those who are killed by various diseaes, heart attacks, et cetera. But let's face it, there's no animals nastier than us, no condition of weather or such that really bothers us.

Another God

Aug1-03, 03:17 AM

Originally posted by Adam
Another God
I would, however, suggest that we are mostly beyond one facet of evolution, that being natural selection. Nah, I don't think we are beyond Natural Selection at all. Sure, we have levelled out the evolutionary terrain some, we are free to move from unlikely phenotype to unlikely phenotype without as severe a punishment as some other organisms, but there is still selection in action maintaining a whole host of necessary genes. Selection in process maintaining various character traits and removing others (people who, say, uncontrollably **** on everyone they meet probably won't have many offspring). There is sexual selection. There is a form of selection for probably the first time in natural history, where a class of humans are simply "Choosing" to not have children. This is selecting against that type of genotype.

Resistence to bacterial infections, resistence to Viruses, cancer resistance are all under the scrutiny of selection. Heart 'disease' is even under selective pressure. As these diseases quickly become the largest killers in our society, our society is weeding out the people who succumb to them and creating hosts of people who don't. It's a gradual process, but it is happening.

So yeah. Here again is my problem. I can present pretty much every argument concievable For Evolution still occuring, and just about no arguments against it....

Deslaar

Aug2-03, 12:05 AM

When I hear the quetion "Are humans evolving?" I often take it to mean evolving in a particular direction; that particular characteristics are being selected for and others are being selected against. If this is what you mean then I think that a case could be made that we are not.

If you are instead suggesting that humans are evolving in the sense that individuals are subject to selection pressure and differential reproduction then obviously we are evolving. All life is evolving in this sense even if it's at hasn't really "evolved" for millions of years eg. the coelacanth. I would say that the principle force involved in human evolution would be stabilising selection.

Chemicalsuperfreak

Aug2-03, 01:37 AM

Originally posted by Deslaar
When I hear the quetion "Are humans evolving?" I often take it to mean evolving in a particular direction; that particular characteristics are being selected for and others are being selected against. If this is what you mean then I think that a case could be made that we are not.

If you are instead suggesting that humans are evolving in the sense that individuals are subject to selection pressure and differential reproduction then obviously we are evolving. All life is evolving in this sense even if it's at hasn't really "evolved" for millions of years eg. the coelacanth. I would say that the principle force involved in human evolution would be stabilising selection.

I think that certain populations are evolving, that is by your suggestion of being selected against. It's not some grand morphological change, but considering how many millions of Africans are contracting HIV, most will be dead, but there's got to be at least a few with natural immunities.

But I think you've got to look at something else besides selection. Travel is so easy nowadays that there are a lot more people with different national heritages. Take my Scottish/Japanese friend for instance. There's a lot of new phenotypes out there. So genetic drift is a serious consideration.

And giving how quickly humans have ****ed up the environment, antibiotics, etc. we'll have to worry about all kinds of selection real soon. Biologically speaking.

Phobos

Aug4-03, 06:22 PM

A.G. - The best I would expect is that human evolution has recently slowed (time of 'stasis' perhaps) due to our global coverage & transportation technologies. I.E., we don't have many significant isolated populations anymore in order to affect larger differences. But I don't expect that to be a permanent condition (and they're still be small changes in the population during that time).

Phobos

Aug4-03, 06:27 PM

Originally posted by O Great One
or

3) they only reproduce after their own "kind"

That's still evolution (so called "microevolution"). For example, if you think a single wolf "kind" was aboard the Ark, and that kind spread across the world and developed into the gray wolves, arctic wolves, timber wolves, etc....that is still a speciation event(s) that qualifies as evolution. Actually, evolution doesn't even require speciation...just statistical changes in the frequency of alleles (expressed genes) from generation to generation. Your concern, I assume, is macroevolution (from one kind to another). But I don't want to get off on a tangent here...

DrChinese

Aug19-03, 11:50 AM

Taking the negative side:

Obviously the forces of natural selection and random mutation are still at work. But is there any "net" evolution considering mutations which die out?

Each of us has different DNA, even identical twins do not always have 100% identical DNA (considering replication errors). So what is the precise definition of human DNA?

The issue presumably is whether a new genetic mutation common to all humans could develop. And to this, I believe the answer is NO. The population of humans is too large, and even over a very long period of time I am not sure it would be possible in humans.

FZ+

Aug19-03, 07:50 PM

The issue presumably is whether a new genetic mutation common to all humans could develop. And to this, I believe the answer is NO. The population of humans is too large, and even over a very long period of time I am not sure it would be possible in humans.
Er... does evolution even work like that? I would think a more probable scenario is that the differing conditions (one might imagine H G Well's the Time Machines's Eloi and Whateveritsnameis) would create a greater divergence within the species, and then we get competition both in genes and overtly, and so we have one dominating and decreasing the prevalence of the other. I don't really imagine that whole populations just uniformly change.

As to the question... Gee... devil's advocate. I suppose at some time you have to define a benchmark at which something is evolving or not, and you can set us as not evolving by definition. Maybe.

Another God

Aug20-03, 08:41 AM

Well, anyway, the debate is next week and I am on the affirmative side after all.

Turns out the affirmative isn't quite so certainly guaranteed going to win as I initially though. As long as humans can control our environment forever, and sexual selection is largely driven by cultural pressures (media etc), then the only selective pressures are purifiying pressures (ie: The pressures which make us keep what we need to stay alive/function practically), which means we won't be evolving at all.

I can't imagining us maintaining absolute control over our environment though. One day, some virus will get through and strike nearly all of us down before medicine can react. A commet will get through our defences. We will colonise other planets and it will create situations we can't control. We will run out of food. We will run out of space. The earth will flood. Bill Gates will buy out a political region, raise an army and kill all 'Jocks', thus providing a selective pressure to be a nerd.... Etc

Any number of unforseen circumstances could arise, and selection will begin once again, and our massed numbers of variety will be selected against.

FZ+

Aug20-03, 07:19 PM

Erm... there are always some form of selective pressure. Like a selective pressure nowadays to be slim (or not). And it's always useful to be smarter... sort of.

And I really don't think we have an absolute control on our environment at all...

Another God

Aug20-03, 07:52 PM

Originally posted by FZ+
And I really don't think we have an absolute control on our environment at all... No we don't, but we have a large enough control (or capacity to control) which allows us to remove any selective pressure before it can have an evolutionary effect... Remember, evolution usually takes quite a long time before anything can happen....we act much quicker than that.

And 'being smarter helps'....helps what? Helps you survive? Not really, anyone can survive in our society. Helps procreate? Not really...I'd say on average stupid people have tons more children than smart people....

LURCH

Aug20-03, 10:09 PM

Originally posted by Another God

And 'being smarter helps'....helps what? Helps you survive? Not really, anyone can survive in our society. Helps procreate? Not really...I'd say on average stupid people have tons more children than smart people....

I would agree with that last observation. However, (and this is assuming intelligence is hereditary) this should result in a larger number of "stupid people" in the next generation. The tendancy of one type to procreate more prolifically results in the more of that type in future generations, causing the entire species to resemble that type. So, if the whole human race gets dumber as a result, then that is evelution. Just not of a type we like to think about ("EVILution? [<:)] ).

Phobos

Aug21-03, 01:55 PM

DrChinese - Evolution is not just mutation. Consider gene flow (changes in population demographics). Right now, there are many varieties ("races") of our species. As our intermingling increases (loss of isolated tribes, improvements to global transportation, urbanization), the traits that we currently use to distinguish a "race" will likely be merged. Statistically, the overall human gene pool will be different than that of today's. I certainly agree that, due to our large & mobile population, it would be very difficult for a new mutation to take hold everywhere. It usually takes an isolated subgroup of an overall population (Mars colony?) in order for a mutation to get a foothold.

A.G. - Overall, I can agree that human evolution may have slowed due to our technology, etc., but not stopped.

As far as brains being helpful...it was a great help getting us this far (spreading across the globe). Now it's being put to a new test...internal (intraspecies) competitions now that our ecological niche is filled. Can we get along or will we kill each other? Or perhaps it will help us reach new niches....or save us from the next comet strike.

DrChinese

Aug25-03, 12:16 PM

Originally posted by Phobos
DrChinese - Evolution is not just mutation. Consider gene flow (changes in population demographics). Right now, there are many varieties ("races") of our species. As our intermingling increases (loss of isolated tribes, improvements to global transportation, urbanization), the traits that we currently use to distinguish a "race" will likely be merged. Statistically, the overall human gene pool will be different than that of today's. I certainly agree that, due to our large & mobile population, it would be very difficult for a new mutation to take hold everywhere. It usually takes an isolated subgroup of an overall population (Mars colony?) in order for a mutation to get a foothold.

A.G. - Overall, I can agree that human evolution may have slowed due to our technology, etc., but not stopped.

You are right of course. Additional mutation does not have to occur for the human race to change its makeup. But the question is really: what DNA defines a human (or any species)? Specifically? How can future evolution be measured? Interesting questions, at a minimum.

pmb

Aug26-03, 03:18 PM

Originally posted by Another God
I've got myself into a debate about whether Evolution is currently occuring in Humans.

So far, with my initial thoughts on the subject, no matter how I approach the topic, I can only formulate Affirmative arguments. Can anyone think of any sort of case that can be built against the stance that humans are currently evolving just like everything else?

(Even if you need to 'select' your definitions, choose your versions of evolution, your types of selection or whatever...)

How could someone conclude otherwise?

Another God

Aug27-03, 05:26 AM

Originally posted by pmb
How could someone conclude otherwise? By claiming that humans have controlled their environment, so that we adapt the environment to us, and there is no selective pressures adapting us to the environment.

pmb

Aug27-03, 02:04 PM

Originally posted by Another God
By claiming that humans have controlled their environment, so that we adapt the environment to us, and there is no selective pressures adapting us to the environment.

We don't really adapt to our environment - that's not what evolution is about. The idea is that random mutations happen. The mutations which favor the propagation of these 'mutated genes' are the ones which will dominate. So we don't adapt per se.

And mutations happen all the time - most of them are caller "cancer" since some of the mutations go crazy

Pete

Phobos

Aug27-03, 02:16 PM

Originally posted by pmb
We don't really adapt to our environment - that's not what evolution is about. The idea is that random mutations happen. The mutations which favor the propagation of these 'mutated genes' are the ones which will dominate. So we don't adapt per se.

And mutations happen all the time - most of them are caller "cancer" since some of the mutations go crazy

I think I agree with this, but I think adaptation is still a good word to use. Natural Selection acting upon the variation within a population (resulting from mutation and other things like gene flow & recombination) is a kind of adaptation. e.g., objectively, environmental conditions like climate may preferentially select for more hair/less hair (or whatever trait) already present within a species...but subjectively (in hindsight perhaps), it seems like the population is adapting to the new climate. But I suppose your point is that the variation is the source of change, not the environment. On this matter, I would note that some variations are caused by environmental conditions, such as bacteria that start swapping genes at a faster rate or that reduce DNA-repair mechanisms in times of environmental stress.

Phobos

Aug27-03, 02:18 PM

Originally posted by Another God
By claiming that humans have controlled their environment, so that we adapt the environment to us, and there is no selective pressures adapting us to the environment.

Maybe someday we can consider this once the words "natural disaster", "disease", etc. are no longer needed in our language. We're still up to our ears in these things (especially in third-world countries where a significant fraction, if not the majority, of the human populaton lives).

selfAdjoint

Aug28-03, 07:41 PM

Even if there were no selective pressure in modern life (which I do not believe), there would still be evolution, through Neutral Evolution. This is just drift caused by the accumulation of variances. And mutative variances are ocurring, every individual, I have read, has several of them in their genome.

You can't decide what's adaptive and what's not from looking at a life style that's only a century or so old. Our cities, and our welfare programs, won't last forever.

Another God

Aug29-03, 12:22 AM

Originally posted by selfAdjoint
You can't decide what's adaptive and what's not from looking at a life style that's only a century or so old. Our cities, and our welfare programs, won't last forever. That was precisely my argument as the affirmative. Well, basically anyway, except that I didn't say that drift is evolution, I agree with Dennett's thing that Evolution is Heredity, Variation and selection, and so at the moment we are building up headps and heaps of variation, with only a little slection...but the selection will come later. We can't avoid it, it wil happen eventually. Evolution is all three of those things, and just because wee can't always see all three of them, doesn't mean we don't have evolution at those times.

So atm, we are varietising.

Later, we will be being selected, and the mass of variation will be important.

selfAdjoint

Sep1-03, 12:29 PM

You know there is some evidence of varietilization in present day human populations. I am not talking about the phenotypic "races" because true interfertility is common between them, but many couples (I once heard the number 10%) cannot have children. Much of this has to be variation (i.e. mutation) to the point of reproductive isolation. Nobody I know studies the systematics of such cases, but it would seem to be "evolution (at least variation) in action".

And of course this happens quite randomly with respect to our perceived causes and differences. That is what you would expect. Variation has no relation whatsoever to selection. To suppose otherwise is Lamarckism.

Mentat

Sep4-03, 03:11 PM

I just found this thread, and I must say that the challenge looks even harder at this point than it did when I first read the title (and then I thought it was very close to impossible - and only added the "very close" because I don't want to be closed-minded).

Heck, even if you could stop all of genetic recombination/variation, and could ensure that there be no selective pressure ever induced on the species (and this is already pretty well impossible), you would stil have memetic replication and cultural evolution.

Phobos

Sep4-03, 04:12 PM

Originally posted by Mentat
you would stil have memetic replication and cultural evolution.

This is different than biological (DNA) evolution, is it not?

Mentat

Sep5-03, 05:16 PM

Originally posted by Phobos
This is different than biological (DNA) evolution, is it not?

Yeah it is. I guess it could be excluded for the purpose of a purely biological debate.

Mentat

Sep8-03, 12:37 PM

OTOH, memetic evolution still plays a role, since the more culture changes, the more varied the possible selection pressures (on genetic evolution). IOW, if culture continues to evolve, then there is a greater and greater possibility of its (culture's) producing selection pressure.

For example, if more an more cultures started practicing polygamy, then the population density would soon become a "pressure", and could "force" genetic evolution.

Phobos

Sep8-03, 07:02 PM

Good point. I agree. Behavior can affect selection pressures and human behavior (culture) is a rapidly shifting phenomenon.

Mentat

Sep22-03, 12:44 PM

You know, I was thinking about this topic at home, and I came to a possible argument against the idea of current human evolution.

Evolution is not measured by what is happens to the individual, but by what happens to the group (species). Thus, it is not correct to say that humans are Evolving, since the species has not really changed (genetically) since Cro Magnon man. Yes, there is variation, and lots of it, but surely it is not considered evolution for me to say that some giraffes are born with smaller necks than their parents.

What do you think, AG, could this be an argument?

Another God

Sep23-03, 04:55 AM

Originally posted by Mentat
Evolution is not measured by what is happens to the individual, but by what happens to the group (species). Thus, it is not correct to say that humans are Evolving, since the species has not really changed (genetically) since Cro Magnon man. Yes, there is variation, and lots of it, but surely it is not considered evolution for me to say that some giraffes are born with smaller necks than their parents.

What do you think, AG, could this be an argument?
I think you have the right idea, but your argument has no substance. What makes you think humans haven't changed since cro-magnon man? What about the racial diversity? The blond hair - Black Hair, Dark skin - white skin, lactose intolerant - not, those that can drink alcohol, those who can't....etc.

Mentat

Sep23-03, 04:37 PM

Originally posted by Another God
I think you have the right idea, but your argument has no substance. What makes you think humans haven't changed since cro-magnon man? What about the racial diversity? The blond hair - Black Hair, Dark skin - white skin, lactose intolerant - not, those that can drink alcohol, those who can't....etc.

That's variation within the species, which is the key to evolution of the species, but is not in itself an evolution of the species.

For example, let's say that, after many thousands of years, there have evolved lots of different kinds of Brontosaur. Now, these Brontosaurs are being born with many different sizes of neck, which means that some of them can reach the leaves at the tops of trees, and others cannot. Some of them have different shadings of skin (due to geological climate) and thus can withstand different temperatures. The fact remains in this analogy that the species has not evolved, but has just become more diverse. If there were some natural disaster so that the climate was unlivable for certain ones or so that leaves were unreachable for some ones, then "survival of the fittest" would continue to refine this species until it (probably) would look very different, and thus: A new species. However, until that happens, it is still the same species with lots of potential for evolution but no current "need" for it.

I guess what I'm trying to say is that the mutant Lemur with an opposable thumb was not a new species until there started to be lots of them. The new Homo Sapiens Neandertalensis that acted extra smart and looked really odd, wasn't a new species until there started to be lots of them. The species doesn't evolve until more than a few cases of each variation occur.

Does this work?

Another God

Sep23-03, 05:41 PM

In theory, yeah...sorta. Some people like to make that distinction, its just that for me, when I think about evolution, I don't see any point in calling one set of things a species and another set of things not a species (other than as a possible guide to who can mate with who). Evolution occurs in degrees. Evolution is basically all about variation.

Having the Human 'species' varying is just one part of evolution, not a stage that leads to evolution.

Evolution = Variation, Heridty or replication, and a differential fitness which nature 'selects'.

Mentat

Sep24-03, 03:37 PM

Originally posted by Another God
In theory, yeah...sorta. Some people like to make that distinction, its just that for me, when I think about evolution, I don't see any point in calling one set of things a species and another set of things not a species (other than as a possible guide to who can mate with who). Evolution occurs in degrees. Evolution is basically all about variation.

Having the Human 'species' varying is just one part of evolution, not a stage that leads to evolution.

Evolution = Variation, Heridty or replication, and a differential fitness which nature 'selects'.

Yes, of course I thought of this (remember I'm just trying to help come up with an idea, it's a little too obvious that evolution is occuring in humans [:((]).

Ok, basically, my argument is kind of an inverse form of the argument used by laymen to show that evolution is false: We don't see any giraffes growing extra long necks to reach tall trees or gazzelles turning into cheetahs to escape capture. The common response from the learned evolutionist (well the second-most-common response, the most common would be "what an idiot!" [:D]) is "Evolution does not occur at the level of the individual, but at the level of the species. There is constant variation among individual members of a certain group, but never anything that drastically seperates them from their species (actually, this part is debatable too, since not all evolutionary theories are purely gradualistic). It is only under 'selection pressure' that animals of a certain variation are 'more fit' and thus are the only ones that survive, creating their own 'new' species or subspecies".

Of course, this is just how it is responded to a layman, and there is much more to it, but I was merely trying to use this point (that evolution, as it is commonly considered, occurs at the level of subspecies) to form a possible counter-argument to what is really an obvious fact.

Do you think that there is some other way to apply this point? Do you think that we should just abandon this approach altogether (which I've known from the start was rather weak [:((], but figured I'd "put out there" anyway, since no one else seemed to be attempting it anymore)?

Another God

Sep24-03, 07:27 PM

Well, anyway, my report for this debate was due yesterday, so I should actually start writting it now. When I do, I'll post it here....

Phobos

Sep25-03, 12:38 AM

Just a "me too" response to agree with A.G. At its most basic level, evolution is variation, not speciation. A single population can change/diversify (evolve) without splitting into different species. Consider everyone's favorite test case...humans...we started as one population (Out of Africa theory) which has diversified (evolved) into africans, europeans, asians, pacific islanders, inuits, american indians, etc....and yet we're still considered 1 species (not enough genetic/anatomical/behavioral separation to call us separate species). Granted, those examples I listed above (races) are a minor representation of the overall diversity of the human species (i.e., there is more genetic diversity within a race than between races).

Another God

Sep25-03, 03:11 AM

I wonder how much of our variation is simply a consequence of genetic drift and isolated populations, and how much of it is affected by slight selection pressures, or larger selection pressures.

Mentat

Sep25-03, 12:20 PM

Originally posted by Another God
I wonder how much of our variation is simply a consequence of genetic drift and isolated populations, and how much of it is affected by slight selection pressures, or larger selection pressures.

Now that's an interesting question. You should start a thread on it, AG.

Another God

Oct4-03, 11:26 PM

Here's my final report on the topic. Should I put this on PhysicsPost?

------------------------------------
Current Human Evolution
By Shane Greenup

Evolution may be defined with or with out the requirements of selective pressure, but in terms of discussing the possibility of current human evolution it is only sensible to accept a definition that is selection inclusive. Accepting this, fact based arguments which suggest the absence of current human evolution may seems valid, but can be easily refuted on the basis of 4 common misperceptions of evolution that lie as hidden assumptions behind such claims. These four classes of error will be outlined below and the relevance to the types of arguments raised that claim humans are no longer evolving will be made apparent.

Originally, evolution meant ‘unfolding’ [1] and was most often used to refer to the process of development - the unfolding of a series of specific events leading to a final product. For instance, an acorn would evolve into an oak tree, a fetus into a baby. As the world view gradually changed during the enlightenment period of the 18th century - from that of a stationary world created by God into a world which gradually shaped by geological change over a considerable period of time - it was natural that this term should be applied to the ‘evolution’ of the world. The association to biology quickly followed as the idea that species may not be immutable gained favour and several possible theories emerged, including Lamarck’s and eventually Darwin’s. Since this time Evolution came to be particularly strongly associated with biology and the ‘unfolding’ of species over time. Although Ernst Haeckel’s famous claim that ‘Ontogeny recapitulates phylogeny’ may no longer be accepted, the word once used to describe ontogeny was quickly adapted so that phylogeny could be described in exactly the same way: Evolution. From our modern standpoint though evolution is much more explicit than just the unfolding of species - it has come into a much more meaningful and exact description, commonly defined as ‘the change in the gene pool of a population over time.’ [2]

Using this definition, the possibility of questioning whether humans are still evolving is not even worth asking. The simple fact is that change in the gene pool over time in any species is completely unavoidable. Eyre-Walker and Keightley claimed in 1999 that humans have had on average 4.2 amino acid altering mutations every generation since humans separated from chimpanzees [3]. This measurement ignores the synonymous substitution of base pairs, and all of the mutations which occur in the non-translated regions of Genome DNA. Since only about 1.5% of the human genome is translated [4], this number is quite incredible. With this introduction of change every generation, the ‘change in the gene pool over time’ is assured. Genetic drift is another mechanism through which gene frequencies are changed overtime, and its occurrence is an undeniable phenomenon. Chance events lead to the increase or decrease of numbers of a particular gene in a population, occasionally leading to fixation of a gene (no other variants exist) or extinction of that gene.

These two prime examples of random changes in the genetic makeup of populations are accepted biological phenomena which apply to humans as much as any other species. To say that these two phenomena are classified as evolution means to say that Humans evolve. Of this there can simply be no question.

It is therefore clear that another more specific definition of evolution must be used in order for any sort of productive inquiry into this subject to take place. To account for the affect of random changes alone being considered evolutionary a definition that requires a selective pressure can be used. By defining evolution as ‘the change in a gene pool over time due to a selective pressure’ we no longer have the random changes problem, and the people claiming that humans are no longer evolving actually have something that they can use: The possible lack of selective pressures. From now on this will be the meaning of evolution for the rest of this paper.

Evolution may be directed by a number of selective pressures, one being sexual selection, and most of the others falling under the general title of natural selection. Natural selection affects the evolution of species in every aspect of their life, from their developmental rate, to their ability to survive to reproductive maturity, their ability to find and copulate with a mate, the viability of those offspring, and how much longer after sexual maturity/copulation that organism may continue living. Natural Selection is the true driving force behind any sort of adaptive evolution.

With selection included we can now describe evolution according to a theory described by Dennett in 1995 based on the earlier work of Lewontin and Brandon [5]. In this definition evolution is said to occur whenever there is variation, heredity and a differential ‘fitness’ (i.e.: allowing a point of action for a selection pressure). In the case of all biological creatures heredity is an absolute standard which goes without saying. The fact that there is replication of the genetic makeup from one organism into the next generation is the backbone of the process of evolution. It is upon this backbone of heredity that variation may build up, brought about by mutations, and that differential fitnesses may arise and in turn be selected. So the question now becomes, “Do humans have variety in their gene pool, and is there a differential fitness to these variants?”

Those who believe that humans are no longer evolving accept that we have variety. As pointed out above with the previous definition of evolution, we have 4.2 Amino Acid altering mutations every generation, and then we have genetic drift; it is entirely unreasonable to claim that we do not have variety between humans. What they do doubt though, is that there is any selective pressure left. They claim that due to the advent of modern medicine, technology, farming techniques, food distribution, heating and cooling systems etc, there are no longer any selective pressures in our lives to separate the fit from the unfit. The fitness differential is irrelevant in the environment that we have made for ourselves because we do everything we can to make sure ‘everyone’ survives. Additionally, even if some people die to unforseen virus or bacterial outbreaks etc, then although they may die, the reaction of medical intervention will be infinitely quicker than that of the evolutionary adaptation to the new selective pressure, and so no net evolution will actually occur. The capabilities within our modern society and the speed with which our culture adapts to change has completely overruled the process of natural selection and so stopped evolution.

There are several problems with these claims. These problems can be placed into several classes of error including;
1. Misunderstanding the nature and power of Natural Selection,
2. Forgetting other forms of selection, such as sexual selection,
3. Assumptions about the entire world from the specific first world lifestyles of the very people claiming this, and
4. Mistakenly taking the term ‘current evolution’ to mean that evolution must happen before our eyes.

Class 1
The first class of error may actually be the most subtle. It comes from the assumption that selection only works on the more obvious phenotypic traits and little else. In its worst form this error is manifest in the claims that humans are de-evolving (an oxymoron in itself) because we are creating easier lives for ourselves, resulting in future generations who have evolved weak skeletons, fat bodies and slow reactions etc. While an easier life may allow for these phenotypic changes to exist, to say that we would evolve in that direction is to either revert to the previous definition of evolution, or misunderstand how evolution due to natural selection works. Evolution due to natural selection occurs only in such a way that better adapted creatures become more prevalent than less adapted creatures. If bodies with weaker skeletons (for example birds), more fat (for example seals), and slower reactions (for example sloths) were advantageous to humans, then that is how we would evolve. If that happened to be the case, then the irony would then be that these phenotypes would be advantageous (direct inference from how evolution works), and the claims of ‘de-evolutionists’ would be shown for exactly what they are, oxymoronic.

Continued

Another God

Oct4-03, 11:26 PM

The more subtle side of this can be made clear though, in realising that this altering of what is and what is not advantageous from era to era is entirely unpredictable to us. We perceive certain things as ‘good’ attributes (commonly: Sharp teeth, strong muscles, fast runner, intelligence) and other things as ‘bad’ attributes (commonly: obesity, skin prone to sunburn, unco-ordination) and we decide that anything which departs from the good and/or acquires more bad attributes is losing its selective advantage. While this may often be true, the fact of the matter is that our own judgement has been crafted by evolution and we are biased in our judgements towards the things which were adaptive in the past. We have no idea what is going to happen next and so we can’t be sure that our crafted judgements are any longer valid. As well as that we have no way of knowing what hidden benefits may lay under some superficial phenotype. Combine these two consideration and you are faced with a situation in which you may have superficially ‘bad’ (according to our current judgement) phenotypes with underlying attributes which may in the next few hundred generations come to be so advantageous that they create a selective pressure in themselves. Darwin himself observed that “the struggle will generally be more severe between species of the same genus, when they come into competition with each other, than between species of distinct genera,” [6] and so it is with humans already, and probably will continue to become more and more as we reach the limits of our extended niche. What variation it is that holds the key to the adaptive advantage is surely unknown to us, but it seems incredibly unlikely that the advantage will be with those able to outrun or successfully hunt a lion.

On a less subtle level though there is one more element within this class of error that is ignored by people who claim that humans are no longer evolving. Natural Selection is thorough. Amongst all of the variation which we can and cannot discriminate superficially, Natural Selection screens everything. Natural Selection, unlike our ability to pass judgement, is an unrelenting eternal force sifting through every single probabilistic relation within an organism, between members of a community, between organisms in a species, and between an organism and its environment; all at once. To say that modern humans are no longer under a selective pressure is to claim two things: It is claiming that we know what Natural Selection works on; and it claims that we have used this knowledge to control every single instance of potential selective pressure. We certainly do not know this, and we most certainly have not controlled it. Humans are just as subject to selective pressures as every other organism, even if we can’t see them.

Class 2
The second category of error is simply a case of forgetting that there is more to selective pressures than mere survival. The need to procreate is just as important in evolution, and to procreate humans need to find mates. Sexual selection is present throughout nature and is undoubtedly present in Homo sapiens too. One theory even claims that our enlarged brains, our paedomorphic ape appearance, the size difference between males and females, and various other factors are all consequences of sexual selection [7]. Medicines, technology and abundant shelter will never affect the role sexual selection plays in the evolution process, but culture itself may. It is almost impossible to guarantee that our sexual desires, choices and behaviours are guided by our own and our potential mate’s genetic make up, rather than being guided by the culture we live in. To make it a little more complicated, its not even easy to figure out whether our culture is largely guided by our genetic make up, and therefore only an intermediate between our genes telling us what we want and what we actually choose. Whatever the case one fact remains: Sexual selection - on whatever level – occurs. As long as it continues to occur there will be a selective pressure present, and evolution will occur.

Class 3
The third category of error is the belief that the entire world is like the society we are lucky enough to live in. A society where medicine is provided for everyone, where housing is plentiful, where there is available electricity, running water etc. The fact of the matter is that this isn’t the case at all, but instead around 80% of the world’s population lives in developing countries [6]. If we are to talk about the evolution of Humans and we want to focus on one lifestyle, it would in fact make much more sense to focus on developing countries and talk about their way of life. Of course though, if we were to do this, then most of the points raised about medicines, technology, distribution of food, and general ease/comfort of life would no longer apply, and there would be no case. Obviously when the claim ‘Humans are no longer evolving’ is made, the claim is actually meant to be ‘Humans in developed countries are no longer evolving.’

Class 4
The fourth class of error actually intermingles with every other class on some level. Evolution takes many thousands of years to occur and must be discussed accordingly. To talk only about the way things are now and then to try to infer facts about evolution from that flash of existence, is to fall into this error.

This particular error is all encompassing in its nature and is the sort of error that humans are very prone to make. Being organisms that deal with time in units like seconds, minutes, hours, years, and even up to decades, the concept of hundreds of years or several hundred years turns into ‘A long time’ and nothing else. To think of a hundred years, is to think of something only just graspable. To think of a thousand years though, is really something beyond our grasp and we tend to resort to ‘a really long time’ and that is as far as our imagination goes. We may be able to grasp some sort of awe over the length of it, but we do not comprehend it. Tens of thousands of years, millions of years, billions of years all meld into this one conception of ‘a really long time’ and nothing else. There is little meaning in any of it. To then speak of evolution, something which takes thousands of years for any real changes to start being apparent, is to talk of something which we can’t grasp the timeframe of. Falling into this class of error when talking about Evolution is almost inevitable for anyone not consciously aware of this problem.

Understanding now that evolution only works over the course of many thousands of years means that the claim that ‘humans are no longer evolving’ translates into ‘humans will not evolve at all over the next few thousand years’. Realising this, to maintain the claim that humans are no longer evolving is to claim that our control over our environment is so all encompassing and so certain that nothing that happens will break our control. It is a claim that we will never run out of food, that our population growth will never reach maximum capacity, that rising waters will never cause massive loss of farmland or living space, and that no virus or bacterial pathogens will ever break out into a pandemic. It is to claim that humankind has already completely conquered nature in all of its forms.

Whether we accept evolution as something that occurs with or without a selective pressure, the arguments presented to show that humans are no longer evolving tend to become meaningless in light of how evolution actually works. The points may seem valid in some regard, but they all miss a vital point somewhere and so can be easily shown as the empty claim they are. Humans are varied, humans are being selected, and a time will come not so far off in the future when massive selection may be applied as a consequence of our own actions. Humans are still evolving.

References
1. Webster’s 1828 dictionary, http://www.christiantech.com/
2. Chris Colby. Introduction to Evolutionary Biology, Version 2. 1996. http://talkorigins.org/faqs/faq-intro-to-biology.html
3. A. Eyre-Walker, P.D. Keightley. 1999. High genomic deleterious mutation rates in hominids. Nature 397:344-347
4. B Alberts, A Johnson, J Lewis, M Raff, K Roberts, P Walter. 2002. Molecular Biology of the Cell 4th Edition, Chapter 4, p 202, table 4-1.
5. D Dennett. 1995. Darwin’s Dangerous Idea: evolution and the meaning of life. New York. p 343
6. C Darwin. 1859. The Origin of Species, first edition, reprinted in penguin classics 1985, chapter 3:p127.
7. D Brin. 1996. Neoteny and Two-Way Sexual Selection in Human Evolution. Journal of Social and Evolutionary Systems 18(3):257-276
8. http://www.unfpa.org/sustainable/demographics.htm

Pauly Man

Oct5-03, 01:21 AM

I like it AG. I would recommend posting it on PP.

Originally posted by Another God
I wonder how much of our variation is simply a consequence of genetic drift and isolated populations, and how much of it is affected by slight selection pressures, or larger selection pressures.

I think that our variation is a consequence of the competition between drift and selective pressures. Drift increasing variation, and selection decreasing variation.

As an after thought, I seem to remember looking at a related avenue of interest with you AG. When we looked at evolving a piece of text. I still have the roar data of the computer experiments I ran, which show a simple form of genetic drift in action. I never really ran any useful selection simulations, as we canned the experiment. But if we wish to look into this deeper perhaps this data could be useful, if recode the original code from the stone age code it is presently.

Mentat

Oct6-03, 01:10 PM

Excellent work, AG! [:)]

Yes, by all means post it on PP. If your feeling like embarrasing some other forums, just post a link to this post on there. Hey, we might get some new members out of that. [:D]

Hwarang

Mar13-05, 08:35 PM

Evolution works like this-

You get a whole lot of people. Then put them in some environment and let them live there. If the environment is safe and warm than survival is easy. If the environment is hell then natural selection kicks in. Only the smart or strong or both will survive. The smart or strong will continue breeding eventually a genetic mutation occurs which creates a human that is slightly different than the other humans. This might give the guy or gal a slight edge in surviving as well as getting mates. Because of this that mutant will mate a lot more often and spread his/her genes. In turn the offspring might also possess this advantage and breed more easily as well. Eventually several mutations will occur over millions of years until they become different species.

So yes, we are evolving. Unfortunately evolution does not mean that you will evolve into a higher form of life. We are actually devolving. According to statistics the people who reproduce the most often happen to be the criminals and low IQ people. Due to birth control products(smart people are more successful with them) and the fact that smarter people choose to have less children the IQ average of most of the worlds is dropping. Yes, we are getting dumber. The weak and dumb are allowed to live. This also means that a chance of a negative genetic mutation is much greater than a positive mutation. It also means that the a negative mutation will also be able to survive due to liberal society.

Of course this will take millions of years and by then humans will have either

A. blown ourselves out of the water.
B. Something blows us up
C. We genetically create supermen using technology

IQ and brain size is dropping in American faster than any other race or group has in history.

An average of 0.7 IQ points is being lost in whites, even more points is lost for blacks due to larger percentage of criminals. Of both races, criminals and low IQ people mate the most often. This is the exact opposite of the world over 100 years ago where only the smart and successful had lots of children. The people who also get abortions tend to be able to pay for them. Our IQ might level off until we hit the low 70s -60s possibly 50s in several hundred years if we don’t do something about it. An IQ that low does not mean your mentally retarded with the inability to talk and walk properlly. You can still function in society with an IQ in the 50s-70s, its just that your mental age would be the equivalent of say an average 5-8 year old.

Of course if averages continue like that, civilization will collapse and survival of the fittest will occur raising averages again.

Evo

Mar13-05, 09:53 PM

Bartholomew

Mar13-05, 11:09 PM

From what I've read, fluid IQ (reasoning skill) has been increasing, and static IQ (knowledge) has been decreasing.

Chronos

Mar13-05, 11:15 PM

hitssquad

Mar14-05, 01:09 AM

Our IQ might level off until we hit the low 70s -60s possibly 50s in several hundred years.... An IQ that low does not mean your mentally retarded with the inability to talk and walk properlly.An IQ below 70 would be in the mentally-retarded range.

--
mental retardation is generally thought to be present if an individual has an IQ test score of approximately 70 or below.
--
http://www.aamr.org/Policies/faq_mental_retardation.shtml

Adult dogs typically have adult-human-equivalent IQs of below 20. It can be observed that they can typically walk and run with great agility. Typical 4-year-old humans have adult-equivalent IQs of 25. It can be observed that they can typically walk well.

You can still function in society with an IQ in the 50s-70s, its just that your mental age would be the equivalent of say an average 5-8 year old.--
In adults, an IQ of 50 approximately represents the intellectual capacity of the average eight-year-old, who is able to read simple texts and do simple arithmetic but is not capable of functioning independently.
--
(Richard Lynn. Eugenics: a Reassessment (http://www.amazon.com/exec/obidos/ASIN/0275958221). p65.)

--
Among adults, an IQ of 35 is approximately equivalent to a mental age of 5 1/2 years....
--
(Ibid. p98.)

--
An adult with an IQ of 56 has a mental age of nine years, that is to say, has the abilities of the average nine-year-old. The average nine-year-old can read popular newspapers with ease and make sensible suggestions for the solutions to simple crossword puzzles.
--
(Ibid. p223.)

In other words, a typical 100-or-below IQ-score for an adult can be transformed into mental age by multiplying by 0.16 (or by dividing by 6.25).

Adult IQ Mental Age (of)

6.25 1 year
12.5 2 years
18.75 3 years
25 4 years
31.25 5 years
37.5 6 years
43.75 7 years
50 8 years
56.25 9 years
62.5 10 years
68.75 11 years
75 12 years
81.25 13 years
87.5 14 years
93.75 15 years
100 16 years

Hwarang

Mar14-05, 05:01 AM

Oh no, your wrong, births today are hitting the dysgenic path.

http://www.eugenics.net/papers/eb8.html
http://www.eugenics.net/papers/evidence.html

Notice that the average criminal has lower IQ than the median, they also reproduce the most often. Also notice that the smartest people are the most successful in using birth control products. They are also wealthy enough to afford abortions. The low IQ and even criminals reproduce more often

Also an IQ rise from the early and mid 1900s is not surprising. People were being fed more and more access to schools due to people moving out of farms and into cities with better education. Today however there is no excuse for dropping IQ points. In the early 1900s as well, the rich people also had lots of offspring so it leveled off. However with the mass introduction of birth control products the situation has changed.

And to the other guy, mind telling me what “correct” evolution is then?lol

Phobos

Mar15-05, 07:20 PM

We are actually devolving.

Note that there is no such thing as "de-evolution" (that would imply an erroneous march-of-progress model). Evolution is simply change. A population's characteristics will shift toward whatever best survives. For example, whales did not "devolve" legs and revert back to fish fins in their transition from land to sea...they evolved something new (although similar, given the similar environment). Evolution does not proceed up and down a particular genetic scale...it produces variations in populations that are put to the test.

And a footnote on the IQ discussion...IIRC, an IQ of 100 is defined as "average". So, even if we were 50% smarter/dumber, the average would still be 100. Of course, we can still talk about relative IQ changes.

guevaramartyr

Mar17-05, 11:13 PM

think about what type of evolution you are discussing. micro evolution (changes within indivduals or a species) is certainly occurring (resistance to disease, height change, etc) while macroevolution (change from one species to another) is much more vague. extreme mutations that usually die aside, i haven't heard of any human that cannot breed with another member of the species so far.

Ouabache

Mar18-05, 01:27 AM

I'd like to add a couple of examples of genetic mutations and their impact on human evolution.

I remember from a genetics course, the gene responsible for sickle cell anemia (HbS), also confers some immunity to malaria (which can come in handy if you lived where malaria is common). If you carried both alleles of the sickle cell gene, your chances of survival diminish due to anemia. However if you carry only one sickle cell allele and the other is normal (heterozygous genotype), you have a much better chance of surviving malaria and reproducing. Those not carrying this mutation, are more likely to die from malaria.
If you're really curious about how this sickle gene is beneficial in resisting malaria see ---> http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.html

Another mutation that has entered our gene pool is \delta 32 mutation on gene CCR5. This mutation has been found to exist in the human genome at least for 4,000 years. Those who were carrying it in Europe during the Black Plague epidemic in the 14th century, were immune to plague and survived to pass along their genome to future generations. Today it has been found that those who carry this same mutation, when infected by HIV, have a strong resistance to AIDS. (the mechansim for resistance is also similar to black plague, preventing infection of white blood cells).

In terms of evolution, these and various other mutations have provided a means of survival of humans under hostile environments. Granted these conditions were not global, but if they were, we have the means to survive to another generation.

As a species, we are still only newcomers on the block, having been around a mere 30,000 years... Before us, Neanderthal (Homo neaderthalis) was the dominant hominid for 170,000 years. It is likely, in the course of evolution, that we are not the last hominid to populate the world.

Billy T

Mar18-05, 08:43 PM

I like to add a couple of examples of genetic mutations and their impact on human evolution. ...gene responsible for sickle cell anemia (HbS), also confers some immunity to malaria...Another mutation that has entered our gene pool is \delta 32 mutation on gene CCR5. ...Those who were carrying it in Europe during the Black Plague epidemic in the 14th century, were immune to plague ......As a species, we are still only newcomers on the block, having been around a mere 30,000 years... Before us, Neanderthal (Homo neaderthalis) was the dominant hominid for 170,000 years. It is likely, in the course of evolution, that we are not the last hominid to populate the world.I knew of first alredy, but not the second. In attachment, I offer a different type of mutation which may explain why we dominated all other humanoids so quickly, doing in even the bigger brained and much stronger Neanderthals. It explains a lot of other things as well. What do you think of this idea?

Hwarang

Mar21-05, 08:36 PM

Usually the bigger and denser your bodies are the more brain tissue is needed to control bodily function. This explains why taller people have larger brains than shorter people yet that doesnt make them smarter.

Neanderthals were the warrior class of the hominids. Their bones were much thicker and denser than ours. Their muscles were much heavier and strong. Their nose was shaped uniquely. I guess due to all this heavy body functions they needed larger brains to control bodily function. Brains also differ differently. A brain with more vein like connections will be much more efficent and "smarter" than a brain of equal size yet less sophistication. I guess Neanderthals didnt have the connections necessary to compete with humans.

However one thing people seem to forget is that during the prime of the Cro Magnons, the Cro Magnons averaged brains 25% larger than todays Europeons. Other human groups in the past had brains as larger or larger than the Cro Magnons. Im guessing Humans back then had brains larger than Neanderthals.

Gold Barz

Mar21-05, 08:43 PM

Could neanderthals have, if they were never wiped out and we were the ones who did, developed similar to us obtaining human-like intelligence?

nipwoni

Mar24-05, 01:36 PM

Have you considered Hardy-Weinberg Equilibrium? If a population is in "equilibrium," it is not evolving at all. There are 5 requirements for a population to be in equilibrium:
1. No natural selection
2. No sexual selection (all mating is completely random and all individuals produce the same # of offspring)
3. No net mutation (any mutations that do happen are canceled out by mutations in the opposite direction)
4. No migration into or out of the population
5. The population is infinitely large (so genetic drift has no effect)

The human population does not meet any of these requirements except #4, so it must be evolving. In fact all populations are evolving since it is impossible to meet all of them.
This only applies to microevolution though.

Phobos

Mar24-05, 03:23 PM

Could neanderthals have, if they were never wiped out and we were the ones who did, developed similar to us obtaining human-like intelligence?

It's possible, but not a necessary next step. (i.e., they could have kept evolving in many different ways, but there's no set path to our intelligence)

For what it's worth, Neandertals are considered to be "human" too...just a different species of human (genus Homo).

nipwoni

Mar24-05, 05:25 PM

Neandertals are actually part of the same species as us- they were Homo sapiens neandertalis. Anthropologists think they could have interbred with Cro Magnons, although I think the current consensus is that they didn't contribute much to our gene pool, if at all.
Also, their large brains probably went along with high intelligence, probably as high as ours though in different ways. Certain parts of their brains were larger than ours and certain parts smaller. So, since their intelligence had a different emphasis from ours, they likely would have evolved down a different path.

The Cro Magnons back then did not have larger brains than the Neandertals. The Neandertals had the largest brains (even compared to their body size) of any hominids.
I don't think there's any evidence to show that Neandertals had less connections in their brains than modern humans. I think the main reason they died out was because they were so adapted to the northern European ice age climate. They had to survive in a very harsh, extreme environment, and were successful for hundreds of thousands of years. But they were so specialized that they couldn't compete with a newer, more flexible form, Homo sapiens sapiens, when we started to spread into Europe.

Something many people don't realize is that there have been many species and subspecies of hominids and humans over the last 7 million years or so, often more than one at once. Sometimes they managed to coexist, but usually one outcompeted the other. This means that we are probably not the last species of human. Eventually something in the environment will change and force us to change too, or one group of humans will branch off and become something new, and Homo sapiens as we know it will disappear. So, just because a species went extinct doesn't mean it was a failure. It will probably happen to us someday, and many of those species lasted much longer than we have so far.

Billy T

Mar25-05, 02:36 PM

...Something many people don't realize is that there have been many species and subspecies of hominids and humans over the last 7 million years or so, often more than one at once. Sometimes they managed to coexist, but usually one outcompeted the other. ....You obviously know more about this than I do (assuming you are not just making things up), but I am impressed by the "Out of Africa" event of approximately 50k years ago. Nothing like it had happended in several million prior years - (rapid expansion of one small group to domonate/ eliminate all others).

I am obviously biased as I think it may be related to the strange view I hold about perception in the attachment. What do you think? Why, in less than 20k years, was it all over for the "others"?

SaPhZ

Mar26-05, 06:26 PM

We will get less intelligent; Studies show that University graduates are far less likely to have children.

selfAdjoint

Mar26-05, 08:06 PM

We will get less intelligent; Studies show that University graduates are far less likely to have children.

It is a fallacy that because the people who exhibit a trait have fewer children therefore the number of people in the population who exhibit that trait will decrease. Even for a single Mendelayev trait, with alleles B and b, where the recessive variation requires a bb gene match to be displayed, having the bb bearers create NO children would still leave half the population (the Bb's) carrying the gene, under equilibrium, and from their mating new bb individuals would continue to be born at a stable rate. Intelligence is evidently caused by a number of genes, so the number of people carrying the necessary recessives would be even larger.

In the middle ages of Europe, the intelligent boys were systematically steered into the monasteries, where they did not contribute to the next generation (only the somewhat less intelligent became parish priests who often cohabited and had children). But when the renaissance came there was no dearth of intelligent people from that strong anti-intelligence non-breeding program.

matthyaouw

Mar27-05, 03:07 PM

Also- Who is to say that intelligence is brought about by genetics rather than upbringing?

1,1,2,3,5,8,13,21

Mar28-05, 09:44 AM

I've got myself into a debate about whether Evolution is currently occuring in Humans.

So far, with my initial thoughts on the subject, no matter how I approach the topic, I can only formulate Affirmative arguments. Can anyone think of any sort of case that can be built against the stance that humans are currently evolving just like everything else?

(Even if you need to 'select' your definitions, choose your versions of evolution, your types of selection or whatever...)

if you go back in history, 200-300 years ago the mid 5 foot range was normal for humans, George Washington was 6'5", which was very, very tall for back then. Is this evolution, or are we just finding better food and nutrition to make us taller? :confused:

Fibonacci

hitssquad

Mar28-05, 11:01 AM

Even for a single Mendelayev trait, with alleles B and b, where the recessive variation requires a bb gene match to be displayed, having the bb bearers create NO children would still leave half the population (the Bb's) carrying the gene, under equilibrium, and from their mating new bb individuals would continue to be born at a stable rate.Are you saying the fixing of traits (http://www.google.com/search?q=trait+fixed+breeding) in biological populations is impossible?

Phobos

Mar28-05, 12:44 PM

Neandertals are actually part of the same species as us- they were Homo sapiens neandertalis.

There has been a debate as to whether Neandertals were a subspecies (as you say) or a separate species (H. neaderthalensis). My understanding is that the mainstream view is that Neandertals were a separate species.

Hwarang

Mar28-05, 12:59 PM

George washington was tall because he had good nutrition and was lucky enough to recieve better height genes. We arnt growing taller though. The Human genome has a maximum limit to how tall we can get. Im estimating the maximum height to be about 7,8 for males and 7,2 for females. Despite this maximum its still possible to get even taller if you suffer from that pituatary gland abnormality(the gland over produces human growth hormone). For example Robert Wadlow who suffered from that condition grew to be 8,11 whiles his genes probally told him that he was only suppose to be around 5,8 in height. Because of this he suffered horrible knee problems and died during his early 30s.

In the future we might see some 1st world nations reach their maximum height with people average in the 7 foot range. This is unlikely though, as height on that range produces a lot of disadvantages.(Buildings will have to be completly re-constructed to accomodate the new taller people, people of that height will have to consume much more food and energy in a world of limited energy and resources, height in that range is much harder to work in and much more clumsy for daily works). In fact I think height will probally decrease in the far future to the 5,5 or less range. Im serious here. Smaller people will consume less resources than much larger people. Which means there will be more smaller people. Which means more brains which means more innovation.

Height for modern first world nations will probally level off at 6,3-5,10 average for males unless a eugenics program is introduced to to purposely increase height to the 7 foot range. Of course certain groups will have taller averages and max heights. Africans will be the tallest. In fact the Tutsi's in Africa averages over 7 foot in height during their peak after selective breeding.

Oh yeah and I found a intresting link regarding neanderthals.

http://en.wikipedia.org/wiki/Homo_neanderthalensis

it says that neanderthals had brains 10% larger than modern humans today. Which is impressive, however the cro-magnons for example had brains 25% larger than modern humans. And dont forget that neanderthals had stronger, heavier bodies which meant more brain was needed to control bodilly functions. Another way to measure intelligence was comparing the tools both sides made. If I remember correctly, the humans made much better tools and had a advantage of unique throwing spearings fire with some wooden shaft which neanderthals didnt. Also there has yet to be a single human with neanderthal genes in them. Neanderthals and Humans could not mate.

tobias087

Jan24-10, 07:23 PM

I think that because of modern circumstances, some of the conventional rules of evolution will have to be thrown out the window. For example, in the above predictions about the evolution of height in man in the future, it's assumed that reaching a maximum height is economically undesireable because it puts a strain on resources (ie. tall people need to eat more).

However, while this might be a factor for animals in the wild with scarce food supplies, man, in developing countries at least, has no such scarcities. Most people simply do not die from starvation in developed countries in a systematic way caused by food scarcity. If people are hungry, they can easily find more food, at very small marginal cost. Evolutionary economics are a thing of the past. (Not to imply that there aren't hungry people, but even the homeless don't usually die of starvation)

What we should do to examine current trends in evolution is go back to first principles. It would be tempting to list causes of death and declare that humanity will evolve to be less susceptible to these, there's a fundamental flaw there: most of the current leading causes of death (heart disease, cancer, stroke, etc.) are not things that kill people before they have had children. If a cause of death systematically ends people's lives after they've reproduced, then there is no selection pressure to develop immunity to it.

The better approach would be to consider causes of death in the age bracket where people have not yet had children. In the USA for ages 15-24 (which is below the average age of becoming a parent of 25) the leading cause of death is accidents, and the leading type of accident is car accidents, which account for 25% of deaths in this age group. Since food economics are no longer an issue (or are at least only a minor one) we should expect then that people will develop traits that help them survive car crashes (possibly thicker bones or something like that), since that is the main selection pressure in the developed world.

As with regard to the claim that humans are currently in stasis, in between phases of relatively fast evolution, that makes little sense. What we should expect in evolutionary trends is for organisms to evolve to the point where they are best matched for their environment. Then, if the environment stays constant, phenotypes should tend to stay constant since there is no natural selection impetus, disregarding sexual selection and drift. In humans, we do NOT see a constant environment. In fact, our environment has been changing spectacularly rapidly in the last few thousand years (and even faster in the last few hundred). We should expect then, that humanity will evolve rather quickly to meet its new challenges.

Sorry about the long post! Just had a lot to say.

DaveC426913

Jan24-10, 07:28 PM

Sorry about the long post! Just had a lot to say.And only five years late... :wink:

tobias087

Jan24-10, 08:21 PM

haha, no time like the present

Bodicea

Jan28-10, 06:49 AM

I would think that there must be a limit to certain aspects of evolution within the human body. Eg. height. If we evolve into heights of 7 or 8' then how will the heart cope with it. personally I think there is a limit to how tall we can grow.

Intellect? apprently our brains are growing bigger, and its occured over the last 100 years, but the skull hasnt grown, so the brain is liimited by the the size of the skull, which in turn is limited by the size and strength of the neck. So imho, we are limited physically and intellectually...

However, how we use what we have is changing, and there may well be huge room for development in that area....Are our children actually smarter, or, are they using their brains in a different way due to all the technology that is around. From a very young age they are learning to hone incredibly spatial awareness, hand eye coordination via games consoles.....

So, even though there may be physical limitations to our evolution, I'd say there is definte potential for evolution within the confines.