Evolution of the brain

[popeye18]

I have been thinking lately of human intelligence and the human brain. Let’s take a look at "the great leap forward" 40,000 years ago. This is the time that things like musical instruments, cave drawings, ornaments started to emerge, and it seems they began to appear very fast. Before this they were pretty much nonexistent. It seems that humans became significantly smarter over a very short amount of time. Physically however, we have not changed in close to 100,000 years. Is it possible for the brain to evolve without changing physically? Would this not mean that the brain evolved with the ability to adapt and improve? That would seem an example of forsight which supposedly evolution does not have.

[kerowo]

We may have had the big brains but not big societies to take advantage of them with. Until you get a fairly sophisticated societies there isn't enough time to sit around and think crap up, you are too busy finding food.

[popeye18]

[ QUOTE ]
We may have had the big brains but not big societies to take advantage of them with.

[/ QUOTE ]

But why did we have the brain if we didnt need it?

[kerowo]

Why do you think every bit of our bodies are there for a reason?

[luckyme]

[ QUOTE ]

But why did we have the brain if we didnt need it?

[/ QUOTE ]

Aren't you confusing "not needing it" with "using it for a different purpose". By your argument the brain we have at 18 is overdeveloped because we can still put it to better use once we get our MBA.

Perhaps a week hunting antelope with rocks and/or spear thrower may convince you that the brains we have for driving a honda are overdeveloped because we can add anteloping to our skill set.

You are assuming a fact not in evidence.

luckyme

[popeye18]

[ QUOTE ]
[ QUOTE ]

But why did we have the brain if we didnt need it?

[/ QUOTE ]

Aren't you confusing "not needing it" with "using it for a different purpose". By your argument the brain we have at 18 is overdeveloped because we can still put it to better use once we get our MBA.

Perhaps a week hunting antelope with rocks and/or spear thrower may convince you that the brains we have for driving a honda are overdeveloped because we can add anteloping to our skill set.

You are assuming a fact not in evidence.

luckyme

[/ QUOTE ]

OK i understand what you are saying. Let me try and explain my thoughts more clearly...

Why was our brain complex enough to encompass the new skills of the great leap forward if we never needed these skills before?

[knowledgeORbust]

Evolution makes small, random, genetic mutations within a species. The organism either survives more or less handily with the new mutation. So our brain got more complex a tiny bit at a time, but that little bit of extra brain-power was always useful for some thing. Faster learning curve, increased memory, increased abstract thinking, whatever, and it always helped.

We're pretty solid physically, so mutations that affect our bodies are less likely to be critical for survival. Mutations that affect our minds, however, affect survival more, and each one will be more noticeable.

So, uh, we never NEEDED the skills, I guess, but the increased "complexity" seems to prove handy for survival.

[luckyme]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]

But why did we have the brain if we didnt need it?

[/ QUOTE ]

Aren't you confusing "not needing it" with "using it for a different purpose". By your argument the brain we have at 18 is overdeveloped because we can still put it to better use once we get our MBA.

Perhaps a week hunting antelope with rocks and/or spear thrower may convince you that the brains we have for driving a honda are overdeveloped because we can add anteloping to our skill set.

You are assuming a fact not in evidence.

luckyme

[/ QUOTE ]

OK i understand what you are saying. Let me try and explain my thoughts more clearly...

Why was our brain complex enough to encompass the new skills of the great leap forward if we never needed these skills before?

[/ QUOTE ]

Why did we evolve the dexterity, strength, endurance, balance to win a Tour de France 100's of thousands of years before anyone even thought about a wheel let alone a bicycle? If evolution doesn't have a goal we shouldn't have that ability before we discover bicyles.

luckyme

[popeye18]

[ QUOTE ]
Why did we evolve the dexterity, strength, endurance, balance to win a Tour de France 100's of thousands of years before anyone even thought about a wheel let alone a bicycle?


[/ QUOTE ]

I understand what you are saying. We can ride bikes now because the physical skills needed to do this well are skills we needed 50 thousand years ago for things like hunting and surviving ect. However 50 thousand years ago, for example, what did we use our memory for? It seems today's man has way more things that go into his memory than his ancestors of this time.

[popeye18]

Wanted to add one of the reasons i began wondering about this.

Apparently our brain is twice as big as habilis' was 2 million years ago. It seems that the intellectual diffrence between us now and sapiens 100 thousand years ago is alot bigger than the intellectual diffrence between habilis and early sapiens.

Also a question...If an average human from 50 thousand years ago was born in todays world how would he differ, if at all, from us intellectually.

[thylacine]

[ QUOTE ]
Wanted to add one of the reasons i began wondering about this.

Apparently our brain is twice as big as habilis' was 2 million years ago. It seems that the intellectual diffrence between us now and sapiens 100 thousand years ago is alot bigger than the intellectual diffrence between habilis and early sapiens.

Also a question...If an average human from 50 thousand years ago was born in todays world how would he differ, if at all, from us intellectually.

[/ QUOTE ]

No. Pretty much the same brain, just different culture and different environment. The point is that this brain (e.g. from 50 thousand years ago) had already evolved to be able to cope with a huge variety of situations. So rapid cultural development did not require any further corresponding brain evolution. Moreover those brains (from 50 thousand years ago) were certainly needed at that time to cope with whatever situations they were in.

[luckyme]

[ QUOTE ]
It seems today's man has way more things that go into his memory than his ancestors of this time.

[/ QUOTE ]

Really? people can't get the words to their national anthem right in spite of hearing/singing it since they could walk, our ancestors could recite the complete Iliad or their cultural equivalent, navigate through an area they only passed through once before and without streetnames, recognize and use a bunch of green looking plants and maintain complex social relationships.

The interesting question is why we aren't smarter now with all the learning aids we have, starting with written language.

luckyme

[KipBond]

[ QUOTE ]
[ QUOTE ]
It seems today's man has way more things that go into his memory than his ancestors of this time.

[/ QUOTE ] The interesting question is why we aren't smarter now with all the learning aids we have, starting with written language.

[/ QUOTE ]

I think "we" are smarter. But, with the removal of most of the natural selections, a lot of us aren't. It seems that the disparity is widening. I'm hoping genetic engineering will save us -- let's hope the stupid people aren't allowed to stop that from happening, though. Making abortion & sterilization free & legal might help, too.

Reminds me of the movie, Idiocracy (http://imdb.com/title/tt0387808/). Very funny -- because it's true.

[vhawk01]

[ QUOTE ]
[ QUOTE ]
We may have had the big brains but not big societies to take advantage of them with.

[/ QUOTE ]

But why did we have the brain if we didnt need it?

[/ QUOTE ]

To nail co-eds.

Seriously.

[Lestat]

[ QUOTE ]
[ QUOTE ]
Wanted to add one of the reasons i began wondering about this.

Apparently our brain is twice as big as habilis' was 2 million years ago. It seems that the intellectual diffrence between us now and sapiens 100 thousand years ago is alot bigger than the intellectual diffrence between habilis and early sapiens.

Also a question...If an average human from 50 thousand years ago was born in todays world how would he differ, if at all, from us intellectually.

[/ QUOTE ]

No. Pretty much the same brain, just different culture and different environment. The point is that this brain (e.g. from 50 thousand years ago) had already evolved to be able to cope with a huge variety of situations. So rapid cultural development did not require any further corresponding brain evolution. Moreover those brains (from 50 thousand years ago) were certainly needed at that time to cope with whatever situations they were in.

[/ QUOTE ]

I'll just add that we have MUCH more free time now to devote our brain to other things. Perhaps more than 50k years ago, we didn't have the luxury of sitting around playing around with different pigments of color and creating art. Today, we have the luxury of trying to figure out how to smash an atom to create the greatest amount of energy.

LuckyMe and other make a lot of sense. We did possess similar intelligence 40,000 years ago. We were just using it for different things (mainly survival). As we became more and more advanced, it freed up our time to turn our intelligence to more scholarly and artsy things. It's over 100 degrees right now in the western United States. But few people are overly worried about how to keep their infants alive in that heat. They'll flick a switch and turn on the air conditioning. Now they can turn their attention to more important things. Like the All-Star game Tuesday night.

[popeye18]

Hmmm yea, humans 50k years ago probably did have knowledge vasly greater than i am giving them credit for.

What made the brain double in size between habilis and sapiens?

[vhawk01]

[ QUOTE ]
Hmmm yea, humans 50k years ago probably did have knowledge vasly greater than i am giving them credit for.

What made the brain double in size between habilis and sapiens?

[/ QUOTE ]

I already told you.

[Rduke55]

[ QUOTE ]

No. Pretty much the same brain

[/ QUOTE ]

I'm not so sure about that. While I'd be amazed if the cultural changes didn't have a huge part to play in the great leap forward (Ramachandran talks about this idea using the industrial revolution as an example), the assumption that the brain was pretty much identical is shaky to me. People depend too much on the brain size information. It really doesn't tell you a whole lot in many cases because you could have the same size brain, even with all the same nuclei and cortical areas, with just seemingly subtle connection differences and it's a wildly different organ with wildly different functioning. Several neuro types have postulated some sort of this playing a role in the great leap foward, often with things like mirror neurons (which actually fit in pretty nicely with the environmental/cultural changes idea).

[vhawk01]

[ QUOTE ]
[ QUOTE ]

No. Pretty much the same brain

[/ QUOTE ]

I'm not so sure about that. While I'd be amazed if the cultural changes didn't have a huge part to play in the great leap forward (Ramachandran talks about this idea using the industrial revolution as an example), the assumption that the brain was pretty much identical is shaky to me. People depend too much on the brain size information. It really doesn't tell you a whole lot in many cases because you could have the same size brain, even with all the same nuclei and cortical areas, with just seemingly subtle connection differences and it's a wildly different organ with wildly different functioning. Several neuro types have postulated some sort of this playing a role in the great leap foward, often with things like mirror neurons (which actually fit in pretty nicely with the environmental/cultural changes idea).

[/ QUOTE ]

Is there anything special or unique about the brain that would lend weight to the idea that it may have evolved more rapidly than "what we'd expect" or anything like that? Basically, any reason to think that 100,000 years is enough time for significant brain evolution?

[Rduke55]

[ QUOTE ]
Is there anything special or unique about the brain that would lend weight to the idea that it may have evolved more rapidly than "what we'd expect" or anything like that? Basically, any reason to think that 100,000 years is enough time for significant brain evolution?

[/ QUOTE ]

Yes, the human brain seems to have evolved in a very short (by evolutionary standards) amount of time. Papers use terms like "surprisingly rapid"

There is even a term - "Human Accelerated Regions" - for some of the DNA parts that are thought to be involved in this evolution.

There are several explanations that could contribute to this. Some people believe that species with more advanced brains evolve quicker because they often have smaller population sizes. Smaller population sizes certainly have an effect on the speed of evolution and humans are prime examples of small population sizes for most of our history.

Also, we're not talking about huge genetic changes here. Even very subtle changes in the genetic code can have large effects on the brain's development and connections which have massive effects on function and behavior.

[vhawk01]

[ QUOTE ]
[ QUOTE ]
Is there anything special or unique about the brain that would lend weight to the idea that it may have evolved more rapidly than "what we'd expect" or anything like that? Basically, any reason to think that 100,000 years is enough time for significant brain evolution?

[/ QUOTE ]

Yes, the human brain seems to have evolved in a very short (by evolutionary standards) amount of time. Papers use terms like "surprisingly rapid"

There is even a term - "Human Accelerated Regions" - for some of the DNA parts that are thought to be involved in this evolution.

There are several explanations that could contribute to this. Some people believe that species with more advanced brains evolve quicker because they often have smaller population sizes. Smaller population sizes certainly have an effect on the speed of evolution and humans are prime examples of small population sizes for most of our history.

Also, we're not talking about huge genetic changes here. Even very subtle changes in the genetic code can have large effects on the brain's development and connections which have massive effects on function and behavior.

[/ QUOTE ]

Cool, got any papers that are particularly interesting about this? I'm ridiculously bored this summer.

[Rduke55]

Check out Amadio and Walsh. Brain evolution and uniqueness in the human genome. Cell. 2006 Sep 22;126(6):1033-5. and read the papers they reference.
Also, some recent ones are:
Pollard et al., Nature 443, 167-172

Pollard et al., PLoS Genet. 2006 Oct 13;2(10):e168.

Dorus et al., Accelerated evolution of nervous system genes in the origin of [censored] sapiens. Cell. 2004 Dec 29;119(7):1027-40.

As a related aside, Dorus also took a look at molecular evolution and female promiscuity.
Nat Genet. 2004 Dec;36(12):1326-9.

Here are a couple papers that suggest a lot of brain-specific genes actually evolve slower than other genes. They are interesting for Other reasons as well.

Zhang L, Li WH (2004) Mammalian housekeeping genes evolve more slowly than tissue-specific genes. Mol Biol Evol 21: 236–239.

Duret L, Mouchiroud D (2000) Determinants of substitution rates in mammalian genes: Expression pattern affects selection intensity but not mutation rate. Mol Biol Evol 17: 68–74.

Caceres M, Lachuer J, Zapala MA, Redmond JC, Kudo L, et al. (2003) Elevated gene expression levels distinguish human from non-human primate brains. Proc Natl Acad Sci U S A 100: 13030–13035.


And I always recommend it, but if you want something interesting and not bogged down in technical molecular crap you may want to pick up Striedter's "Principles of Brain Evolution". It may be in your library.

[Taraz]

[ QUOTE ]

Yes, the human brain seems to have evolved in a very short (by evolutionary standards) amount of time. Papers use terms like "surprisingly rapid"

There is even a term - "Human Accelerated Regions" - for some of the DNA parts that are thought to be involved in this evolution.


[/ QUOTE ]

I can just see theists' mouths watering about this one. "See, God did that, it was too fast for evolution!!!"

[thylacine]

[ QUOTE ]
[ QUOTE ]

No. Pretty much the same brain

[/ QUOTE ]

I'm not so sure about that. While I'd be amazed if the cultural changes didn't have a huge part to play in the great leap forward (Ramachandran talks about this idea using the industrial revolution as an example), the assumption that the brain was pretty much identical is shaky to me. People depend too much on the brain size information. It really doesn't tell you a whole lot in many cases because you could have the same size brain, even with all the same nuclei and cortical areas, with just seemingly subtle connection differences and it's a wildly different organ with wildly different functioning. Several neuro types have postulated some sort of this playing a role in the great leap foward, often with things like mirror neurons (which actually fit in pretty nicely with the environmental/cultural changes idea).

[/ QUOTE ]

A key point is that 40k years ago, humans were already somewhat spread around the globe, so it's hard to see how such changes could be universally made, and made quickly. But about 100k or 80k or so years ago, humans went more localised and went through somewhat of a bottleneck AFAIU, so that seems like the time for more rapid evolution.

[Rduke55]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]

No. Pretty much the same brain

[/ QUOTE ]

I'm not so sure about that. While I'd be amazed if the cultural changes didn't have a huge part to play in the great leap forward (Ramachandran talks about this idea using the industrial revolution as an example), the assumption that the brain was pretty much identical is shaky to me. People depend too much on the brain size information. It really doesn't tell you a whole lot in many cases because you could have the same size brain, even with all the same nuclei and cortical areas, with just seemingly subtle connection differences and it's a wildly different organ with wildly different functioning. Several neuro types have postulated some sort of this playing a role in the great leap foward, often with things like mirror neurons (which actually fit in pretty nicely with the environmental/cultural changes idea).

[/ QUOTE ]

A key point is that 40k years ago, humans were already somewhat spread around the globe, so it's hard to see how such changes could be universally made, and made quickly. But about 100k or 80k or so years ago, humans went more localised and went through somewhat of a bottleneck AFAIU, so that seems like the time for more rapid evolution.

[/ QUOTE ]

Well, I think the Toba event 70K years ago and the "Adam" data saying 60K years ago would be bottlenecks (if they actually were bottlenecks) that may be more relevant. Hell, some people think bottlenecks occur through the end of the Pleistocene. In any case I'm not sure you'd need an extreme bottleneck for this.

[vhawk01]

[ QUOTE ]
Check out Amadio and Walsh. Brain evolution and uniqueness in the human genome. Cell. 2006 Sep 22;126(6):1033-5. and read the papers they reference.
Also, some recent ones are:
Pollard et al., Nature 443, 167-172

Pollard et al., PLoS Genet. 2006 Oct 13;2(10):e168.

Dorus et al., Accelerated evolution of nervous system genes in the origin of [censored] sapiens. Cell. 2004 Dec 29;119(7):1027-40.

As a related aside, Dorus also took a look at molecular evolution and female promiscuity.
Nat Genet. 2004 Dec;36(12):1326-9.

Here are a couple papers that suggest a lot of brain-specific genes actually evolve slower than other genes. They are interesting for Other reasons as well.

Zhang L, Li WH (2004) Mammalian housekeeping genes evolve more slowly than tissue-specific genes. Mol Biol Evol 21: 236–239.

Duret L, Mouchiroud D (2000) Determinants of substitution rates in mammalian genes: Expression pattern affects selection intensity but not mutation rate. Mol Biol Evol 17: 68–74.

Caceres M, Lachuer J, Zapala MA, Redmond JC, Kudo L, et al. (2003) Elevated gene expression levels distinguish human from non-human primate brains. Proc Natl Acad Sci U S A 100: 13030–13035.


And I always recommend it, but if you want something interesting and not bogged down in technical molecular crap you may want to pick up Striedter's "Principles of Brain Evolution". It may be in your library.

[/ QUOTE ]

Thanks for the list, and I just checked, that book IS in my library at school. I'll go pick it up tomorrow.