Is Human Evolution Limited by Physical Constraints?

[Mentat]

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]

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

 

[Mentat]

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]

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]

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]

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]

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 occurring 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!" ) 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 separates 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]

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]

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]

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]

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]

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 without 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]

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]

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]

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.

 

[Hwarang]

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 possesses 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]

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 possesses 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.

Actually IQ is increasing, your information is inaccurate. Yes, I have the data to back that up, I just don't have the time to dig it out right now. It's already been posted in other threads here.

edit: Here's one I just found (I'm not on my usual computer and don't have access to my bookmarks). "A line on a graph corresponding to test scores climbs steadily from 1930 to 1990. In just 60 years, the IQ of the average person in the United States has gone up almost 20 points."
http://www.rps.psu.edu/0309/iq.html

 

[Bartholomew]

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

 

[Chronos]

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 possesses 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.

That might be the most amazing post I've ever seen - notice I did not use the word intelligent. Evolution does not work that way.

 

[hitssquad]

Conversion of adult IQ to mental age

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. . 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
[b][color=darkred]25           4 years[/color][/b]
31.25        5 years
37.5         6 years
43.75        7 years
[b][color=darkred]50           8 years[/color][/b]
56.25        9 years
62.5        10 years
68.75       11 years
[b][color=darkred]75          12 years[/color][/b]
81.25       13 years
87.5        14 years
93.75       15 years
[color=darkred][b]100         16 years[/b][/color]

 

[Hwarang]

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]

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]

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]

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]

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]

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 doesn't 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. I am guessing Humans back then had brains larger than Neanderthals.

 

[Gold Barz]

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]

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]

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]

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]

...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]

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

 

[selfAdjoint]

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]

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

 

[1123581321]

I've got myself into a debate about whether Evolution is currently occurring 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?

Fibonacci