Is Human Evolution Limited by Physical Constraints?

[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

 

[hitssquad]

Fixing of biological traits - possible or impossible

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 in biological populations is impossible?

 

[Phobos]

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]

George washington was tall because he had good nutrition and was lucky enough to receive better height genes. We arnt growing taller though. The Human genome has a maximum limit to how tall we can get. I am 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 completely re-constructed to accommodate 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. I am 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 interesting 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 don't 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]

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]

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

And only five years late...

 

[tobias087]

haha, no time like the present

 

[Bodicea]

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 occurred 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.