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Author Topic: Why has our evolution been so different/dramatic to that of our ape cousins?  (Read 5330 times)

Offline oaty100

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If animals evolve/adapt to suit their surroundings, through natural selection, and we shared a common ancestor with other apes, What was it about our particular 'breed' that caused us to develop so well/quickly, when other primate relatives in the same environment remain pretty much unchanged to this day?

Forgive my ignorance if this is an obvious question, Im sure many people have asked this!
« Last Edit: 23/11/2009 13:21:39 by oaty100 »


 

Offline LeeE

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It's not really true that animals evolve to suit their environment, at least not in the way that I think you mean.

The most important thing about evolution is that it is the result of random mutation.  Evolution can only be said to have occurred when a mutation confers an advantage for the mutated animal over the other non-mutated individuals* in its species.  Furthermore, the mutation must be one that results in the mutated animal being more successful at breeding and passing on its new characteristics than its non-mutated rivals.  Many mutations are likely to occur but the vast majority of mutations will be likely to confer a disadvantage at best, and in most cases will mean the organism isn't viable and will quickly die.

It is not the case then, that humans and the current apes changed themselves from an earlier sub-optimal form in response to the prevailing conditions but that different mutations occurred to that earlier form, both of which just happened to convey an advantage over the earlier form.

*Strictly speaking, there are no non-mutated animals as every different organism that has developed from the initial organism is a mutation.  However, because most mutations fail there tends to be relatively long periods where no change occurs to a species and so during that period the species could be said to be stable.
 

Offline oaty100

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Ok I think I follow! But wouldnt these mutations survival  highlight which attributes are key to survival in a particular environment, and as our ancient relatives came from similar environments i would  expect those mutations that survive to be similar.

I guess im just puzzled about what was so unique about us that meant we carried on progressing, while related apes havent, but still exist, so arent really a weaker mutation, and do rather a good job of survival?, if that makes any sense!!....
 

Offline Andrew K Fletcher

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When mankind stood up and walked on two legs, the bloodflow to the brain and from the brain changed. The holes in the skull that carried the blood from brain to skin migrated from the back of the head to the top of the head.
 

Offline Madidus_Scientia

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and as our ancient relatives came from similar environments i would  expect those mutations that survive to be similar.

Our ape cousins are very well adapted to their environment, the jungle, which is why they haven't changed as much. Humans evolved from a group/s that left the jungle, walking across plains of tall grass, which made it neccessary to stand on two hind legs to see where they were going. Any physical trait that made this new lifestyle easier was selected for.

So it wasn't the same environment, in fact it was the change of environment which initiated our divergence from that common ancestor.
« Last Edit: 23/11/2009 19:54:31 by Madidus_Scientia »
 

Offline oaty100

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I see, well that pretty much clears it up to me!
Is it right to say then, that the increase in our brain size and intelligence is largely due to us begining to walk upright, blood flow to the brain etc?

If this is true I wonder whether we can make monkeys slowly more intelligent by forcing them to walk upright, maybe using some kind of monkey zimmer frame??!
 

Offline LeeE

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You can't really force evolution down a particular path.  Penguins walk upright but it doesn't seem to have made them especially intelligent.
 

Offline Madidus_Scientia

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I'm not sure what Andrew was getting at but no I don't think our intelligence was to do with blood flow to the brain, intelligence depends on the structure and size of the brain not how much blood is in it, the regulation of blood flow would follow as a result of brain size increase I think. Otherwise I would have did all my exams while standing on my head! If anything you would hypothesise less blood flow to the brain when walking upright. I think it was to do with our increased usage of making tools, development of language and memory for better coordinating hunting/living in tribes, navigating, dealing with changing unpredictable climate (having the foresight to ration/store food) and competition with rival tribes/species would favour intelligence too.

There's probably loads of other theories why. I remember reading a thoery that suggested migrating north to colder regions may have helped the evolution of the brain, as our brain generates alot of heat and so brain size may have been limited by how efficiently the body could lose heat, this became less important in colder climates.

I disagree that evolution can't be forced down a path, modern day dairy cows produce much more milk than pre-domestication breeds, thanks to humans selectively breeding them for milk production, bananas used to be barely edible before we started growing only the crops with the highest yield, similar with many other plants. I don't think you'd ever be able to converge the species or anything, they would always be different in terms of DNA, but if you wanted to guide the evolution of chimpanzee's with the goal of making them as intelligent as humans, you could selectively breed only the most intelligent individuals of each generation over a couple of hundred thousand years and they'd get fairly intelligent i'd bet.
« Last Edit: 24/11/2009 17:39:32 by Madidus_Scientia »
 

Offline LeeE

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I'm not sure that you can regard selective breeding as evolution.

As I understand it, although I'm not an animal husbandry scientist, selective breeding is about reinforcing desired characteristics that are already present in the individuals you choose breed.  These characteristics though, while being desirable to the breeder, may not offer any survival or breeding advantages to the animal itself.

Certainly, mutations will occur amongst the individuals that are chosen for breeding but once again, the mutations that are propagated via selective breeding may not be those that would otherwise confer an advantage.

On the other hand though, I guess you could claim that humans are a part of nature and therefore whichever mutation makes them more likely to be kept alive by humans for breeding, instead of culled/cooked, has conferred an advantage.
 

Offline Madidus_Scientia

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On the other hand though, I guess you could claim that humans are a part of nature and therefore whichever mutation makes them more likely to be kept alive by humans for breeding, instead of culled/cooked, has conferred an advantage.

Indeed, they're adapting to their environment, which happens to be captivity.
 

Offline ...lets split up...

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I see, well that pretty much clears it up to me!
Is it right to say then, that the increase in our brain size and intelligence is largely due to us begining to walk upright, blood flow to the brain etc?

If this is true I wonder whether we can make monkeys slowly more intelligent by forcing them to walk upright, maybe using some kind of monkey zimmer frame??!

There are many contributing factors to why we are the way we are.

There's a theory we see colour to differentiate ripe fruit from under-ripe and possibly harmful fruit.

A contributing factor to our intelligence is that our particular homonid ancestor evolved along the east african coast and fed mainly on protien rich fish (brain food). The increase in our head size is why women evolved wider hips (for ease of child birth). Larger heads and smaller bodies also meant that human children were more vulnerable young and needed more care and matured more slowly, meaning that the more socially oriented of the group survived. This was essentially the backbone to communities.

And also, don't forget that you're comparing us to apes when there was lots of competing homonid species at the time, we were just better equiped. When we were way ahead of the competition there was nowhere they could survive without encountering us and eventually they all died out (or were killed by us). So when you compare us to apes it's like comparing an old apple computer with the latest microsoft computer.
« Last Edit: 25/11/2009 19:26:33 by ...lets split up... »
 

Offline glovesforfoxes

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So when you compare us to apes it's like comparing an old apple computer with the latest microsoft computer.

No, it's really not. You could no better function as a gorilla as it could you. A modern microsoft computer can have all the functionality that an old apple one has, and do it better. We do not really "do" evolution better. We did it different, and it wasn't our decision. The anthropocentric attitude seeing other species as somehow lesser is similar to the microsoft computer laughing at the apple computer, even though neither of them chose their capabilities. An animal must be judged not even in the context of it's species ability for the same reason, but it's own, since every single animal is different.
 

Offline ...lets split up...

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Chillax, i'm not prejudice against apes. I love apes, in fact my brother is an ape.I used that example where the idea of the computer is our common ancestor, microsoft is one branch and apple is the other. I say "older" in the sense of degree of change. I could be wrong but i take it apes have been in the same type of environment since we started walking around. And we've been all over, so i assume we've changed more.
 

Offline LeeE

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Flawed Analogy Alert: Just thought I'd better point out that Microsoft doesn't make computers and that there is no such thing as a Microsoft computer.  A better analogy would be with the hardware that makes up the complete system i.e. not just the processor, but all the other gubbins too.
 

Offline ...lets split up...

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I tried to think of a different example but couldn't, i was looking at my computer tower at the time.
 

Offline Andrew K Fletcher

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Madius

Why would the holes have changed location in the skulls of erect humans compared to stooped apes?
 

Offline Madidus_Scientia

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Not sure, possibly due to altered gravitational pressures or thermal efficiency.
 

Offline Andrew K Fletcher

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There is a theory from Dean Faulk called the Radiator Theory, which hypothesises the brain somehow selectively alters the blood flow to cool the brain. There are no valves in the vessels that pass through the skull and Professor Michel Cabanac showed in evaporative heat stress in the head due to exercise can alter the blood flow, completely reversing the flow against the pressure and direction of the heart. Even flowing in two directions in one vessel.

Cabanac accepted Faulk’s hypothesis. I think they have contribute greatly to our understanding of this particular part of evolution by identifying the location of holes changing and the blood flow redirect.

But the brain cannot alter the flow of blood so we are left postulating what can cause it?

Gravity is indeed part of the picture.

Andrew
 

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