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Brain Gain
September 8, 2005 7:29 PM   Subscribe

Genes Reveal Recent Human Brain Evolution. Two important new papers in the journal Science (available here) from the evolutionary geneticist and rising star, Bruce T. Lahn (see this recent profile from The Scientist), are potentially the tips of some very large icebergs. The papers document how two genes related to brain properties that underwent strong selection during the course of hominid evolution, have continued undergoing strong selection since the emergence of anatomically modern man. The papers wonderfully illustrate how biological evolution is an ongoing process as well as the artificial distinction between “micro” and “macro” evolution, and promise to be controversial for two reasons: First, the brain genes underwent the strongest selection during two periods of cultural and technological efflorescence (roughly 37,000 and 5,800 years ago). Second, the genes are distributed very differently in modern human population groups, existing at very high frequencies in some groups and being very rare in others, ensuring that the modern function of these genes will be a source of more research and much impassioned debate. More observations from anthropologist John Hawks.
posted by Jason Malloy (54 comments total) 2 users marked this as a favorite

 
So, it shows that MeFites are evolving more slowly than the rest?
posted by mystyk at 7:39 PM on September 8, 2005


The discovery adds further weight to the view that human evolution is still a work in progress...

How can anyone possibly think evolution just suddenly stopped and is no longer applicable to us? I can't fathom the arrogance required for such a belief...
posted by nightchrome at 7:42 PM on September 8, 2005


William Calvin's Ascent of Man is a great read on his theory of how ice ages put evolutionary pressure on human brain size, with a corresponding increase in intelligence.
posted by Rothko at 7:42 PM on September 8, 2005


Sorry, Ascent of Mind. Darwin's on the brain.
posted by Rothko at 7:43 PM on September 8, 2005


Typical scientist, using facts to back up his claims. What a loony, all hail FSM, the one true creator.
posted by Mr_Zero at 7:48 PM on September 8, 2005


Rothko, William Calvin is excellent. Here's a pointer that would have made a great post by itself, for no charge: William Calvin puts all his great books up on his webpage, where people are free to browse, peruse, scan, scrutinize, and even study them at their leisure. For free. For real. The Ascent of Mind, for instance, is right here. Good stuff.
posted by Jason Malloy at 7:51 PM on September 8, 2005


Um this research is predicated on the assumption that evolution happens, which, as Americans, we know it does not.
posted by Optimus Chyme at 7:51 PM on September 8, 2005


Great post. Thanks!
posted by homunculus at 7:58 PM on September 8, 2005


Someone slap a sticker on Metafilter!
posted by Rothko at 8:13 PM on September 8, 2005


How can anyone possibly think evolution just suddenly stopped and is no longer applicable to us? I can't fathom the arrogance required for such a belief...

The question isn't whether it's happening, but rather on what timeframe. The claim that there is detectable selection going on w/r/t intelligence on the order of just a few millennia is a significant one.

Still reading the article, but I have to admit that I find all the caveats about 'Sub-Saharan African populations' just a little bit disturbing.
posted by spiderwire at 8:13 PM on September 8, 2005


nightchrome: I think the theory is that natural selection (at least in the strictest sense) doesn't apply to civilized humans anymore (or is nowhere near as powerful a force), as we develop technologies to overcome our genetic impairments.

Example: Genes for bad eyesight are no longer weeded out of the gene pool, as those who carry them have no survival disadvantage, due to eyeglasses and contact lenses.


It could be said, then, that natural human evolution has ceased, and that we now guide our own genetic future.
posted by nervestaple at 8:14 PM on September 8, 2005


Darwin's on the brain.

Or Kubrick.
posted by spiderwire at 8:14 PM on September 8, 2005


How can anyone possibly think evolution just suddenly stopped and is no longer applicable to us? I can't fathom the arrogance required for such a belief...

Pretty simply. I'm not qualified to opine as to which belief as valid, but the counter-argument is that civilization creates an environment in which for all but the most terminally stupid the stakes are not life-and-death.

Furthermore, people with higher degrees and higher IQs are supposedly statistically1 less likely to breed.

Thus the argument that civilization prevents evolution. As I said, I have no idea if it's valid, but that's what the argument is, at least.



1I know of no studies demonstrating this, I've just had this 'fact' repeated to me endlessly every time I hear this counter-argument
posted by Ryvar at 8:15 PM on September 8, 2005


nervestaple:It could be said, then, that natural human evolution has ceased, and that we now guide our own genetic future.

Or you could say that we're just under different evolutionary pressures from other species. Whereas a creature in a volatile climate might swiftly select for resistance to temperature changes, the argument that's being made here is that under societal pressures, there's selections going on based on the intellectual (in our era, economic) viability of a potential mate. Not a new claim, but perhaps new proof.

The flip side to your argument would be that if the hypothetical species were in a stable climate, all kinds of vulnerabilities might persist w/r/t temperature tolerance.

Aside: sorry for the flurry of posts -- I should have consolidated, but I like I said, I was still reading :)
posted by spiderwire at 8:17 PM on September 8, 2005


Damn, beaten at the finish line by nervestaple. Here's me not being naturally selected against regardless.
posted by Ryvar at 8:17 PM on September 8, 2005


Ryvar: I know of no studies demonstrating this, I've just had this 'fact' repeated to me endlessly every time I hear this counter-argument

Actually, there was a study on the Ashkenazi Jew population claiming exactly that, apparently pretty controversial, that was posted in MeFi recently. I'm gonna go look for it.
posted by spiderwire at 8:18 PM on September 8, 2005


Ryvar: Damn, beaten at the finish line by nervestaple. Here's me not being naturally selected against regardless.

Actually, I beat you.

OK, using the Preview button this time, for serious. This dynamic preview makes me so lazy.
posted by spiderwire at 8:19 PM on September 8, 2005


Darwin's on the brain.

Or Kubrick.
posted by spiderwire at 11:14 PM EST on September 8 [!]


Or Descent of Man. Or both, probably. I'm off to put an ice pack on my head, anyway.
posted by Rothko at 8:26 PM on September 8, 2005


It could be said, then, that natural human evolution has ceased, and that we now guide our own genetic future.

Nonsense. If the world's population continues to increase, we'll hit a breaking point eventually, and selection will influence the outcome. Granted, quick Googling has indicated that many demographers think that the world population will start to decline in the latter part of this century, but that's clearly a non-intuitive position.
posted by gsteff at 8:27 PM on September 8, 2005


Here's the previous post. Good discussion here, and relevant to this thread.

Specifically, it looks like more than a few people were rightly critiquing the use of IQ as a measure for the Ashkenazi population (a good complaint), but it seems that the authors in the linked article were just looking at... brain size?

Is that a relevant metric? Any neurologists in the house?

Ryvar on preview: I'm off to put an ice pack on my head, anyway.

Trying to speed up the evolutionary process?
posted by spiderwire at 8:30 PM on September 8, 2005


Rothko, actually, spiderwire.

Would sharing his ice pack with you be an example of civilization blocking natural selection?
posted by Ryvar at 8:43 PM on September 8, 2005


How can anyone possibly think evolution just suddenly stopped and is no longer applicable to us? I can't fathom the arrogance required for such a belief...

Well actually this has been around a while. Remember that the underlying mutations that cause evolution still occur, however, given technology, natural selection doesn't occur unless something is a benefit or detriment to survival. Modern civilization has effectively insulated us from most of the survival pressures our ancestors had. Secondly, there isn't population isolation as there was before. The human race, thru inter-racial breeding, are slowly working on a more homogenous genetic makeup.
posted by MrLint at 8:46 PM on September 8, 2005


Very interesting articles. Though I may have to wait for my brain to develop a little further before I make any sort of intelligent commentary. Give me a couple thousand years.
posted by grapefruitmoon at 8:49 PM on September 8, 2005


Just because we don't have the same survival pressures our ancestors had doesn't mean we don't still have survival pressures.
posted by nightchrome at 8:58 PM on September 8, 2005


This still doesn't explain the existence of the Simpson Twins.
posted by ed at 9:05 PM on September 8, 2005


more evidence more evidence
posted by celerystick at 9:36 PM on September 8, 2005


Ryvar: (double checked): Would sharing his ice pack with you be an example of civilization blocking natural selection?

Is that supposed to be some sort of insult? I was just making a lame joke about the whole Ice Age selection thing. I wasn't calling you or Rothko a Neanderthal or anything. :)
posted by spiderwire at 9:38 PM on September 8, 2005


Example: Genes for bad eyesight are no longer weeded out of the gene pool, as those who carry them have no survival disadvantage, due to eyeglasses and contact lenses.

This is a poor example. The "natural" isn't the important part--it's the "selective" part. There still exists tremendous selective pressure on humans today both natural (increasing temperatures) and artificial (smog). 2,000 years is a blip; it's a bit too early to "call" evolution. Anybody who insists otherwise is just throwing out pure speculation. Get back to me in 30,000 years and we can begin discussing the extent of selective pressure on Information Age man.
posted by nixerman at 9:45 PM on September 8, 2005


Furthermore, people with higher degrees and higher IQs are supposedly statistically less likely to breed.

Say this is true. Then it's a perfect illustration that evolution is continuing to occur in the human population, no?
Just not in the direction of higher degrees/IQs.

I was in a small town in Mexico many years ago (Sayulita; at the time they had recently obtained their first phone. now they have a web page) that seemed to have a population of a few hundred. No, they told me, it's more like 3000, but most of them would come up to your knee. Evidently a serious fraction of those kids weren't going to make it. I have never doubted since that natural selection is an important process in humans today.

One more comment on human evolution today, and just how lousy this "we're so coddled today that there's no evolutionary pressure in any direction" idea is. The bower bird enjoys a cushy existence, and is so coddled today that there's no evolutionary pressure in any direction. Yes? No. In fact, while male bower birds can easily bring home the bacon, they can't easily bring home the ladies.

To impress the females, the male builds a big bachelor pad (a "bower") with little function other than to look shweet. One species is particularly into the color blue, and will collect blue flowers, blue butterfly wings, blue feathers from other birds in order to sex up the place. You can watch them arrange their stuff, judge critically, change their mind, rearrange until satisfied. If mean nasty scientists come tromping in and move stuff around, the male bower bird will put it back where it (apparently) belongs.

So long as mating isn't random, evolutionary pressure exists.
posted by Aknaton at 9:51 PM on September 8, 2005


So long as mating isn't random, evolutionary pressure exists.

By 'random' you probable mean 'based on some criteria,' which is obviously the case. But the question, as I understand it, is whether those criteria are genetically determined, rational, and contiguous across the population. (NB: I'm not a biologist, I'm just a MeFite.)

In other words, I can choose a mate based on a set of criteria, but that's a long way from saying that those criteria (my choices) are ingrained because of a selection pressure, or that they have a selective effect -- i.e. an environmental pressure causes that selection to occur across-the-board, and that that pressure has an evolutionary effect.
posted by spiderwire at 10:20 PM on September 8, 2005


Aknaton, nobody refutes that, we simply state that evolutionary pressure in a civilized world is radically different (amongst the well-off portions of the populace at least) from what it was for the billion+ years beforehand.
posted by mek at 10:21 PM on September 8, 2005


Another way of putting that would be: just because mating isn't 'random' (for my parents, whether or not they did acid and liked rock music) doesn't mean that the pressures involved are genetic or evolutionary.

The incredible variance of human societies and mating practices seems to indicate that we could have just put ourselves into a crapshoot phase.

(Ex.: 'Oh, you like the Backstreet Boys? Me too! Tee hee!' Bam. Marriage, babies. --Clearly not intelligence selection at work.)
posted by spiderwire at 10:23 PM on September 8, 2005


Clearly not intelligence selection at work.

Intelligence hasn't really been around long enough to have determined whether or not it is an advantageous quality.
posted by nightchrome at 10:26 PM on September 8, 2005


Intelligence hasn't really been around long enough to have determined whether or not it is an advantageous quality.

Um. The joke was that modern culture encourages conformity rather than intelligence?

If you're being serious, then no, sorry, you're wrong. Intelligence -- assuming it's inherited -- has been an advantageous quality pretty much since the advent of agriculture, and arguably before that.

I'd be glad to hear the argument that logical thought has no relation to survivability. :-/ And here I've been spending all this time in school for nothing...
posted by spiderwire at 12:42 AM on September 9, 2005


Metafilter: Intelligence hasn't really been around long enough to have determined whether or not it is an advantageous quality
posted by Eirixon at 12:46 AM on September 9, 2005


I didn't read the actual Science article (cause i don't feel like registering at yahoo groups), but what is his evidence that these new alleles are correlated to bigger brain size? The NYtimes only says that he examined the differences in alleles across different groups, but it never says he tried to correlate the two new alleles with bigger brain size. I'm very skeptical of the link between these genes and intelligence.

That being said, it looks like he study was well done and I'm glad they showed that humans are still evolving. it's a common misconception that human's are at the peak of there evolution and that if we want to change biologically we will have to use unnatural selection. But it is pretty bold of them to be claiming that these changes coincide with great cultural upheavals, seeing as how they have zero evidence for why that would be true. If anything I would think we would be evolving less intelligence. You have to be smart to survive as a Hunter gatherer. you don't need to be smart to get laid in the modern world

Anyway here's a good link about brain size and it's correlation with intelligence.
posted by afu at 12:57 AM on September 9, 2005 [1 favorite]


In comparison to the length of time that other developed traits have been in use, it seems to me that intelligence is extremely new and untested. It's my impression that sometimes environments change, and traits which were once advantageous stop being so. Sometimes they even become a detriment.
posted by nightchrome at 1:13 AM on September 9, 2005


But wait, how does this fit in with Intelligent Design theory?
posted by moonbiter at 1:14 AM on September 9, 2005


moonbiter, God's currently in his bug-fixing phase.
He released too early, has been getting a lot of Q&A complaints.
posted by nightchrome at 1:19 AM on September 9, 2005


Furthermore, people with higher degrees and higher IQs are supposedly statistically1 less likely to breed.

Not in my family. I've always found smarter people more interested in sex. Albeit kinkier. Perhaps they breed less because they have kids later in life, and therefore have fewer, but better supported children?
- Pure speculation.
posted by Smedleyman at 2:42 AM on September 9, 2005


Nice post, thanks.
posted by OmieWise at 5:58 AM on September 9, 2005


the argument that's being made here is that under societal pressures, there's selections going on based on the intellectual (in our era, economic) viability of a potential mate. Not a new claim, but perhaps new proof.

Actually, the reverse is true. Poor and economically disadvantaged people have more children then the Rich, who often have less then two on average.

So while wealthy people may have better access to more attractive mates, the poor are more 'fit' from a natural selection standpoint.

That said, because the human race is so large, there is not going to be very much evolution. Look at sharks: Millions and millions of years with almost no change. It's entirely possible that humanity could remain 'frozen' from an evolutionary standpoint for hundreds of millions of years.

And as the scientist said: these genes are just one of many, many genes that control for brain size, and there is no corrilation between this particular gene and IQ.
posted by delmoi at 7:31 AM on September 9, 2005


Not in my family. I've always found smarter people more interested in sex.

Anicdote != data.
posted by delmoi at 7:32 AM on September 9, 2005


Also, the Chinese developed writing much earlier then 5,800 years ago, IIRC.
posted by delmoi at 7:33 AM on September 9, 2005


Not in my family. I've always found smarter people more interested in sex.

ALSO, while they may be more intrested in sex (which I doubt) they are much more likely to have access to, understand and understand the importance of birth control.
posted by delmoi at 7:43 AM on September 9, 2005


Fascinating stuff. News bulletin to the myopists who've suggested that human evolution is over (many of them quite recently): It looks like all those tree trunks in your face are obscuring quite the forest.

I'm still waiting for someone to follow up on the research done in the 1960s on how penguins may be more intelligent than man, or at least BBC programmers.
posted by mowglisambo at 9:53 AM on September 9, 2005


delmoi: That said, because the human race is so large, there is not going to be very much evolution.

The size of the species isn't relevant as long as it can be segmented -- like, for example, Galapagos finches. You say:

Actually, the reverse is true. Poor and economically disadvantaged people have more children then the Rich, who often have less then two on average.

But that's not what 'selection' means. 'Selection' has nothing to do with having more children. If that were true, bugs would rule the planet. What it means is that if an isolated group selects for a certain genetically determined trait (like intelligence) then that group would in theory diverge along a different evolutionary path.
posted by spiderwire at 2:17 PM on September 9, 2005


"the Chinese developed writing much earlier then 5,800 years ago, IIRC."

uhhh, where's the support for that? oracle bones are just about 5,000 years old and I don't think there are any really strong claims for writing beyond that.

"But that's not what 'selection' means. 'Selection' has nothing to do with having more children. If that were true, bugs would rule the planet"

eh, you have no idea what selection means, if for a certain species, a significant part of the population is being pressured to having a certain gene, that is natural selection, or are you claiming that groups of humans are going to disconnect themselves from the gene pool and create their own species.

i can't believe the crap science in this thread, no wonder so many people buy intelligent design
posted by afu at 2:28 PM on September 9, 2005 [1 favorite]


"groups of humans are going to disconnect themselves from the gene pool and create their own species."

Six milion years later humans have more in common with the apes than mice with rats. Rats and mice have 10 times the number of differences in their DNA than humans as compared with apes.
posted by sultan at 3:07 PM on September 9, 2005


Also, the Chinese developed writing much earlier then 5,800 years ago, IIRC.
The word you tried to use is "than". Making such a basic error in English makes your argument less compelling.
posted by longsleeves at 6:18 PM on September 9, 2005


afu:eh, you have no idea what selection means, if for a certain species, a significant part of the population is being pressured to having a certain gene, that is natural selection, or are you claiming that groups of humans are going to disconnect themselves from the gene pool and create their own species.

And yet I know how to use the Shift key, and the importance of basic grammar and question marks. Funny how that works, isn't it?

Read the post again, Mendel: What it means is that if an isolated group selects for a certain genetically determined trait (like intelligence) then that group would in theory diverge along a different evolutionary path.

So, in this case, if a certain group of humans is isolated by wealth or some other economic situation (job, trade, country, etc) then they could, in theory, have the isolation that's necessary for local selection.

longsleeves:The word you tried to use is "than". Making such a basic error in English makes your argument less compelling.

Or maybe it was a typo?

Jesus, do you people just wait for threads to move down the front page before you come out of the woodwork? It's like Retard Snark 101 in here.
posted by spiderwire at 8:51 PM on September 9, 2005


Oh yes.

And you also made me forget why I came back here.

What I wanted to point out is, I think, pretty important: the researchers in the above FPP didn't really make the claim that the alleles they identified affected 'intelligence' per se, at least not in the way we usually define it. (IQ, etc.)

The argument they are making -- and this is a good argument -- is that there is at least evidence of selection going on in brain-related genes over a remarkably short period of our evolutionary history.

Just because it's related to the brain (and thinking) doesn't necessarily mean that it correlates to what we think of as 'intelligence.' But it's still a really significant finding as it means that we are selecting much more rapidly that would normally be the case, and we're doing it in specific relation to our brains. Thinking about the issue in that context seems pretty fascinating to me.
posted by spiderwire at 8:54 PM on September 9, 2005


I'm listening to te hardest button
posted by longsleeves at 11:55 PM on September 9, 2005


delmoi:

Definitions of speculation:

* noun: a hypothesis that has been formed by speculating or conjecturing (usually with little hard evidence)

Example: "Speculations about the outcome of the election"

* noun: an investment that is very risky but could yield great profits

Example: "He knew the stock was a speculation when he bought it"

* noun: continuous and profound contemplation or musing on a subject or series of subjects of a deep or abstruse nature
* noun: a message expressing an opinion based on incomplete evidence
posted by Smedleyman at 8:57 PM on September 10, 2005


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