Wake up, and smell the controversy

Posted 12 September 2005 by Mike Dunford

There are a pair of articles in this week's edition of the journal Science that are almost certainly going to cause some excitement and controversy in the field of human evolution. Controversies in this area are nothing new, of course, but these articles seem to have all of the necessary ingredients for a spirited debate. They also seem to be almost certainly destined to be miscited by any number of unsavory individuals. Although the two articles have slightly different sets of authors, both come from the same laboratory, and both focus on the same topic: natural selection acting on genes involved in the development of the human brain. Two different genes were examined, and in both cases specific versions of the genes - alleles - were found to be present in frequencies that indicate that they have recently been (or still are) the subject of strong selective pressure. In both cases, the alleles appear to be very new - younger than the appearance in modern humans. Finally, and here is the bit that's going be the most controversial part of this, the selectively favored alleles are less likely to be present in people from certain geographic locales. Read More (at The Questionable Authority).

35 Comments

Harald Korneliussen · 12 September 2005

Completely uninformed speculation here, but unless people die in large numbers from lack of intelligence, isn't it unlikely that these genes are related to it? After all, "strong selective pressure"?
If I am born in the world today, if I should hazard to guess, I would think that the biggest risk to me passing on my genes would be disease, am I right? The risk from "being too stupid to attract a mate" or "being too stupid to survive to fertile age" would seem pretty small in comparison, wouldn't it?

DrFrank · 12 September 2005

In response to Harold:

This is just an idea for why these genes could be selected for, although I don't pretend to have any hard evidence backing this up :)

If the genes can beneficially affect intelligence, particularly the most recent one, I suppose you might postulate that increased intelligence meant that you had an increased probability of working your way up the social hierarchy as a skilled artisan or some such, to the point where you got to sleep in nice clean accommodation: that reduces your risk of disease, and hence the gene becomes selected for.

Also, you could probably afford to keep more women happy ;)

Like I said, just an idea, but as something so recent I'm thinking that it would really have to make sense in a social context.

I'm not a qualified evolutionary biologist, so feel free to rip me apart - I can take it ;)

DrFrank · 12 September 2005

Sorry Harald, I realised just as I was posting that I'd gotten the spelling of your name wrong.

My apologies.

sanjait · 12 September 2005

I don't really see why it is surprising that humans are still evolving, although it should certainly be interesting to see that more precisely. The chimp genome should certainly keep comparative genomicists busy for a while.
It wasn't until very recently that modern industrial societies came about that allowed people to survive even if they were handicapped or unable to compete in the marketplace. I'm sure there are many places in the world where this still isn't true.
Before that, and after the time humans diverged from chimps, intelligence became more important to many aspects of life. Tool-making ability could give one a decided advantage in hunting, combat, and later in agriculture. Farmers today will also inform you that it is not just a brute force process, but rather a thinking person's vocation as well.
Now, many of these same selective pressures probably aren't present right now in the modern West. Procreation is less correlated with wealth now, and most people survive to childbearing age.
But I'm certain we still have some selective pressures. Does everyone have the same number of children? Clearly not. Are there genetic differences between those who procreate profusely and those who do less so? Probably so. A cynic might even suggest that it is the less intelligent among us who seem to have the most children, while more thoughtful people often delay that decision until later in life, which would lead to a selection against intelligence.
Anyways, a natural strong selective pressure doesn't require people to die in large numbers, at least not at once, to be present and effective. It just requires there to be some significant advantage, which is steadily present over the course of many generations, and in the last 60,000 years it is likely that was one of the drivers of our divergengence from Pan.

Gav · 12 September 2005

er ....... is it safe to assume that alleles selected for over the timescales talked about here actually do predispose towards greater intelligence? On what basis?

DrFrank · 12 September 2005

er... is it safe to assume that alleles selected for over the timescales talked about here actually do predispose towards greater intelligence? On what basis?

Well, from their research it is clear that it has been selected for, and therefore obviously had some kind of positive effect on fitness. Personally, I can't really say anything either way on whether the adaptive advantage came from any increase in intelligence, although the known effect of this gene on the brain at least suggests the possibility. My comment was just an idea about how if the genes do contribute to intelligence, how this might have been selected for in an ancient human society.

Gav · 12 September 2005

Not disputing what you say, DrFrank.

From an ID standpoint though the timing of the ASPM change coincides pretty well with the encounter of King Thamus with the god Thoth. Would help explain the regional variations too.

If Thamus was right, then we'll have got thicker, not sharper.

All in the spirit of helpfulness.

Ken Shackleton · 12 September 2005

Well, from their research it is clear that it has been selected for, and therefore obviously had some kind of positive effect on fitness. Personally, I can't really say anything either way on whether the adaptive advantage came from any increase in intelligence, although the known effect of this gene on the brain at least suggests the possibility. My comment was just an idea about how if the genes do contribute to intelligence, how this might have been selected for in an ancient human society.
— DrFrank

I found estimated age of 37k years to be interesting. Were our ancestors not believed to have developed abstract thought and speech around that time? It was also around that time that our ancestors migrated out of Africa, spread across the globe, and displaced those that they encountered. Perhaps the gene affected brain development and wiring, not just size per se.

ts (not Tim) · 12 September 2005

Perhaps the gene affected brain development and wiring, not just size per se.

Where do such speculations come from? Certainly not from the evidence in the articles in Science. OTOH, the evidence of particularly strong selective pressure, and the geographical disparity, do not seem consistent with a general cognitive capacity, but rather a response to environmental factors such as disease or diet.

sanjait · 12 September 2005

Without examining the article (as I don't have access to Science from home), it seems plausible to have a strong enough selective pressure for some intelligence trait with even low penetrance. 37,000 years was probably around 2000 generations, plenty of time to pick an allele with only a marginal fitness advantage.
Just thinking generally, when some large change occurs in the life of a species, be it an environmental factor or some kind of genetic innovation that changes the landscape, there are many strong selective pressures. An analogy is how quickly HIV mutated after it made the species jump from simians. Genetic drift and selection pressures both likely contributed to much faster mutation since that "speciation" even in HIV than in SIV, by a wide margin.
It seems likely some fundamental innovation, like tool making ability(or we could say "technology") provided a possible entry for a selection for increased cognitive ability. We know there was some significant pressures because humans have deviated greatly from the apes in a relatively short period of time. Of course, there are certainly many genes and alleles involved in that process. But the overall theme is clear; something created a destabilization and after that it was genes gone wild.

Creationist Troll · 13 September 2005

Just a few questions....
How do we know the alleles originated about 37,000 and 5,000 years ago? Obviously we don't.
How do we know that alleles appear through mutation and not some intelligently designed mechanism which creates variation within species?

Flint · 13 September 2005

Troll:

How do we know that alleles appear through mutation and not some intelligently designed mechanism which creates variation within species?

I doubt anyone would argue with you on this point. Some otherwise indetectible mechanism could always have been the agency behind everything and anything. This possibility can never be ruled out, and so might be the case. It might also be the case that we CAN detect this agency in principle, but we currently lack the knowledge, the right senses, the breakthrough of imagination, the appropriate instrumentation, or whatever. So we must muddle along as best we can, generating hypotheses and theories that we CAN test, and as a result of centuries of successful testing, we are inadvertently tricked by our own limitations into believing that our repeated successes mean something. I suggest that we continue along this perhaps misguided path because we find our successful results both satisfying and beneficial, and that these perceived benefits outweigh the philosophical possibility that they have happened essentially by accident, and that the pattern of increasing knowledge they imply is yet another artifact of our limitations.

qetzal · 13 September 2005

How do we know that alleles appear through mutation and not some intelligently designed mechanism which creates variation within species?
— Creationist Troll

As Flint points out, we don't know that with absolute certainty, since absolute certainty doesn't exist. However, random (in the sense of undirected) point mutations are a proven phenomenon, as much as anything can be proven. They have been demonstrated under lab conditions and observed in natural settings hundreds to millions of times over (depending on how you choose to count). An intelligently designed (non-human) mechanism that creates variation within species has never been demonstrated. Don't you think we are justified in preferring explanations based on known mechanisms that provably exist and are fully consistent with the observed data?

Flint · 13 September 2005

quetzal:

Don't you think we are justified in preferring explanations based on known mechanisms that provably exist and are fully consistent with the observed data?

Of course, (essentially) magical explanations are always fully and automatically consistent with ANY observed data. All that's required is a willingness to credit magic as the responsible agency. And at this point, the discussion necessarily veers off in the direction of WHY anyone would entertain this possibility in the absence (or defiance) of observable data. The discussiion simply has no other direction to go. Historical evidence is pretty convincing (at least to me) that people in general are more than willing to trade away utility for certainty, and magical agencies are nothing if not certain (since uncertainty is only possible when observation is relevant). If anything is made clear by these discussions, it's that citing actual evidence implies a serious misconception of the creationist approach. We're really talking about psychological needs that evidence can never satisfy, and the threat represented by anything that can undermine those needs is best met with nice, comfortable denial. I don't WANT that to be true, therefore it is NOT true, therefore I'm still right. And the more everyone arounds me sees things my way, the less discord I suffer. And if this socialization means a short life of misery and disease for everyone, it is still emphatically worth it. The alternative is (shudder) doubt, along with doubt's sibling, change. A terrifying world where nothing holds still, nothing is certain, there are no absolutes, and I might even be wrong. You want me to suffer all this, and all I get in exchange is the speculation that something might be more accurate, as far as someone can tell right now? Are you kidding me?

qetzal · 13 September 2005

Of course, (essentially) magical explanations are always fully and automatically consistent with ANY observed data. All that's required is a willingness to credit magic as the responsible agency.
— Flint

I agree completely. Simple explanatory power is a relatively useless criteria. My (poorly made) point was about known versus unknown mechansims. CT contrasts two possible mechanisms. Each can fully explain all relevant data. Only one is known to exist (as much as anything can be 'known'). The other is entirely hypothetical. Hence my question to CT: in such circumstances, isn't it obvious that we should prefer the known mechanism? I also agree with you on the psychological issues, but only in a Lincoln-esque way. It's not true for all people (or all creationists) all of the time. Maybe CT is unable or unwilling to question his/her beliefs. In that case, nothing I say will matter. But, since CT is here asking questions, and not behaving like an irredeemable troll (such as Davison or evopeach), I don't mind responding.

Timothy Chase · 13 September 2005

I can certainly see how with the wealth effect (children require more investment before they start making returns on investment within more advanced economies -- less advanced ones, you send them out into the field at age four, more advanced, you end up having to send them to college), there might currently be a selection for thickness. However, civilization is fairly recent (last 10,000 years), then we were probably talking about tribes under 100 people before then. If this is the case, then a given allele could easily come into dominance within a tribe, and then those tribes with the better allele would tend to be more successful, less likely to die out, more likely to grow to the point at which they would have to split up into separate tribes.

Tribe-selection, anyone?

Just a thought from an amateur...

sanjait · 13 September 2005

Tribe-selection? Absolutely Tim Chase. Thinking about what the life of a small tribes was like, I wonder if they had any significant provision to ward off inbreeding. In the time before civilization, I doubt it, and if not, the fixation of alleles within tribes would have been pronounced. In this way, tribes that went long times without intermixing would slowly tend toward intratribal homogeneity. But the tribal groups would still presumably be very competitive, thus maintaining a strong selection pressure. The best tribes, not just in terms of strength, footspeed and resistance to disease, but also in management and maintenance of healthy tribal societies, would be the ones who send genes on to the future.

Henry J · 13 September 2005

Timothy Chase,

Re "Tribe-selection, anyone?"

I saw an article not too long ago (maybe right here?) that used that to explain how altruistic behavior can evolve. Tribes with a few altruistic type individuals tend to grow faster than those that don't have them, so even though the altruistic types don't individually outdo their neighbors, their numbers increase with their tribes. Or something like that. In a species not having family groups of some sort, that won't happen.

Flint,

Re "(essentially) magical explanations are always fully and automatically consistent with ANY observed data. All that's required is a willingness to credit magic as the responsible agency."

Consistency is one thing, but to be an explanation, doesn't the conclusion have to be deduced from the hypothesis?

Henry

Flint · 13 September 2005

Henry:

to be an explanation, doesn't the conclusion have to be deduced from the hypothesis?

I think the conclusion need only be accepted. I'd go so far as to say that conclusions deduced from hypotheses (subjected to tests) are the rarefied exception. In the overwhelming majority of cases, due to sheer brute human nature, the conclusion comes first, and observation is used only as a post facto rationalization by those who are more comfortable rationalizing their beliefs rather than simply accepting and holding them de novo. As children, we are (often enough) satisfied with "because I said so" as an explanation. Most of us, as we mature, morph this into "because those I respect say so" - whether these paragons are priests or biologists. I expect priests (clerics generally) outnumber biologists by a margin exactly as wide as the level of difficulty understanding biology as opposed to "godidit." Making the evidence fit the conclusions is a lot easier than it sounds...

'Rev Dr' Lenny Flank · 13 September 2005

How do we know that alleles appear through mutation and not some intelligently designed mechanism which creates variation within species?

Would you mind showing us this intelligently designed mechanism, please? Would you mind showing us what it does and how it creates variation within species?

'Rev Dr' Lenny Flank · 13 September 2005

Thinking about what the life of a small tribes was like, I wonder if they had any significant provision to ward off inbreeding. In the time before civilization, I doubt it

I don't know exactly what you mean by "before civilization", but every human society that has ever been studied firsthand, from the most technoligically simple hunter-gatherers to the most industrialized nation-states, has cultural provisions to avoid marrying within the family group. Indeed, so do chimpanzee troops, which (I am pretty sure) you would not consider to be "civilized".

'Rev Dr' Lenny Flank · 13 September 2005

The best tribes, not just in terms of strength, footspeed and resistance to disease, but also in management and maintenance of healthy tribal societies, would be the ones who send genes on to the future.

I think that human history (including recent history) shows pretty clearly that the society that is best at intimidating its neighbors to do what it wants them to do (or bashes them over the head if they don't) is the one that controls the most resources, and thus runs the show. Strength? Resistance to disease? All you need to dominate the world is a better military than they've got.

Henry J · 13 September 2005

Re "I think the conclusion need only be accepted. I'd go so far as to say that conclusions deduced from hypotheses (subjected to tests) are the rarefied exception."

Hmm. Yes, I suppose the common usage of "explanation" is that way. But, imnsho, a scientific conclusion has to be actually logically implied by the hypothesis being considered - not just associated with it.

Henry

ts (not Tim) · 13 September 2005

Consistency is one thing, but to be an explanation, doesn't the conclusion have to be deduced from the hypothesis?

No, certainly not. The explanation for someone dying may be that they ingested poison, but dying can't be deduced from ingesting poison. And this holds for virtually every explanation, because an explanation does not consist of a complete statement of the causal considerations.

ts (not Tim) · 13 September 2005

Don't you think we are justified in preferring explanations based on known mechanisms that provably exist and are fully consistent with the observed data? Of course, (essentially) magical explanations are always fully and automatically consistent with ANY observed data. All that's required is a willingness to credit magic as the responsible agency.
— Flint

So you think that magical explanations are based on known mechanisms that provably exist? Or do you think that qetzal's qualification was just a bunch of noise words?

If anything is made clear by these discussions, it's that citing actual evidence implies a serious misconception of the creationist approach.

To a large degree, but people debating with creationists generally take on the operating assumption that either the creationist has a chink in their armor somewhere where a bit of rationality might get through, or that someone listening does.

How do we know that alleles appear through mutation and not some intelligently designed mechanism which creates variation within species? I doubt anyone would argue with you on this point.

Your certainty on this point is both amusing and bizarre. I will argue that this is like asking how we know that children's teeth are replaced with money by their parents and not by a tooth fairy.

ts (not Tim) · 13 September 2005

How do we know the alleles originated about 37,000 and 5,000 years ago? Obviously we don't.

Is that a question, or an answer? It's not clear whether this is a pointless assertion of the lack of certainty of all empirical claims, and thus we don't "know" anything (but the numbers are just an estimate), or an ignorant assertion that there are no means for making such estimates.

Flint · 14 September 2005

ts:

So you think that magical explanations are based on known mechanisms that provably exist? Or do you think that qetzal's qualification was just a bunch of noise words?

If I'm interpreting you correctly, the issue here is whether an "explanation" does or does not require a plausible, testable mechanism. If we just make something up of whole cloth, does this qualify as an "explanation" or is it just noise? I attempted to make it clear (with actual examples) that I was talking about whether or not something represented as an explanation was accepted as such. From what you say, you not only reject "goddidit" as an explanation, you reject that this even qualifies as an explanation. For you, this may be the case. For creationists (and perhaps many others), this explanation is acceptably complete and fully satisfactory.

people debating with creationists generally take on the operating assumption that either the creationist has a chink in their armor somewhere where a bit of rationality might get through, or that someone listening does.

I suspect most of us here are playing to the audience most of the time (since our usual flavor of creationist is demonstrably impenetrable). I observe the distinct difference in styles between these debates and debates between Believers.

Your certainty on this point is both amusing and bizarre. I will argue that this is like asking how we know that children's teeth are replaced with money by their parents and not by a tooth fairy.

Since I agree with you completely, I assume we're not communicating. Troll has made a reductio ad absurdum argument, as required by his postulates. Presume that the tooth fairy does the job. Presume that this conviction is not open to question. Now presume that you actually observe parents replacing teeth with money. How can you rectify this? You can reject your observation as an illusion. You can claim that the tooth fairy is acting through the proximate agency of the parents, but is "really" responsible. Ultimately, no weight of observation or consensus can shake your conviction. Creationists have yet to run out of ways to deny inconvenient evidence. And I agreed (I guess you don't) that we can never have absolute knowledge. I went back and re-read the post from which you extracted a single sentence, and found that my subsequent efforts explained and supported that sentence to my satisfaction. Perhaps if you had not omitted the explanation, the sentence you find bizarre would be more meaningful to you...

Creationist Troll · 14 September 2005

Are random mutations responsible for creating the varieties of roses that one finds in nature? It seems absurd to believe that all of the different colored roses are simply the result of random mutations, but then we are left with a problem: if there isn't some kind of mechanism which creates new allels then all of the alleles had to be present in the beginning, which would lead to a situation where there had to be say 300 Adams and 300 Eves. If there were only 2 people then there would only be a maximum of 4 different alleles at each locus. Anyways, I find this absolutely fascinating!

Creationist Troll · 14 September 2005

Here's something that might be an interesting read..
http://www.nwcreation.net/articles/recombinationreview.html

qetzal · 14 September 2005

It seems absurd to believe that all of the different colored roses are simply the result of random mutations....
— Creationist Troll

Why does this seem absurd to you? More importantly, could suitable evidence ever change your mind? If so, what would it take?

...if there isn't some kind of mechanism which creates new alleles....

But we know there is. Mutations create new alleles. Even if you personally don't believe that mutation + natural selection can lead to new species, surely you don't deny that mutation can create new alleles? That's not some hypothesis or theory; it's a direct, logical consequence what an allele is. This comes back to my original question to you. We know mutations happen. We know mutations create new alleles. We have no good evidence for any ID mechanism. Given two alternative proposed mechansims, each of which can fully explain all relevant data, why should we not prefer a mechanism that's proven to really exist, over one that's pure speculation? If we hear hoofbeats, and someome says it's either horses or unicorns, I think you'd agree that horses is much more likely. If you don't think the situation with the alleles is comparable, could you please explain why?

Creationist Troll · 14 September 2005

Creationist Troll wrote: It seems absurd to believe that all of the different colored roses are simply the result of random mutations.... Why does this seem absurd to you? More importantly, could suitable evidence ever change your mind? If so, what would it take?

Random mutations producing aesthetically pleasing varieties of roses? Yes, that is absurd.

We know mutations create new alleles.

Do we?

The mechanisms responsible for the large pools of alleles found within populations today are almost entirely theoretic. Following cell division, we simply can not determine whether mutations or recombination were responsible for any particular genetic alteration.

qetzal · 14 September 2005

Random mutations producing aesthetically pleasing varieties of roses?

No, random mutations merely produce different varieties of roses. Breeders pick the ones that are aesthetically pleasing, and reproduce them in high number. It's actually quite a good model for understanding natural selection.

Following cell division, we simply can not determine whether mutations or recombination were responsible for any particular genetic alteration.

OK, I posted before seeing your link in #48031. I didn't realize you were distinguishing between 'classical' mutations (e.g. base substitutions, small deletions, small duplications, etc.) and recombination. But we still know that mutations create new alleles. If a mutation occurs in a gene, it's a new allele. Unless you deny that mutations occur, it's a given. I suppose what your really getting at is, how do we know that particular alleles arose through mutation (as you mean it), and not through recombination? My guess is, we may not always be able to tell. What's the point of that distinction? Again, based on your link, I'm guessing that you see recombination as the potential intelligently designed mechanism for generating variation. Right? The problem is that there's no evidence that recombination is purposeful in the sense advocated by Ashcraft. His case is based on conjecture, poor reasoning, erroneous conclusions, and simple errors of fact. I'm not interested in posting a point-by-point refutation of his article. If you want to highlight one or two of his arguments that you think are especially compelling, I'll tell you why I think they're wrong. But, first, please tell me whether any amount of evidence could ever change your mind on these issues. If not, if your religious beliefs will always trump any evidence, then let's just agree to disagree and leave it at that. That said, I give Ashcraft real credit for this:

Unfortunately, the creation science community has been denying the existence of new alleles rather than looking to cellular mechanisms for the source. Before the rapid production of diversity can be understood from an intelligent design standpoint, we must first acknowledge that new alleles are accumulating within recognized baramin, and closely investigate these changes.

I think he's wrong in saying there's a teleogic purpose behind recombination. But if he's advocating real bench science to try to prove his point, that's fabulous. If he ever generates compelling evidence, I'll happily change my mind.

Flint · 14 September 2005

Troll:

...but then we are left with a problem: if there isn't some kind of mechanism which creates new allels then all of the alleles had to be present in the beginning...

I find this statement confusing. There are multiple sources of variation: you mention mutations and recombination. These are directly observed, in no way purely theoretical. And when you refer to "the beginning" what are you referring to? Some arbitrary point in the evolution of roses? Your statement is equivalent to saying "but we are left with a problem: if the sun does NOT rise in the morning, then there must have been sunlight present on the very first day." This statement, as with yours, has two major problems. 1) It posits a false premise; 2) It assumes a false model. Basically, you are saying "the evidence be damned, the Designer created everything at once, unchangeable, at some specific point in time." And I agree that if you insist on this model, then actual facts will ALWAYS strike you as absurd.

Mike · 14 September 2005

anyone see any coincidence in the hypothesized timing here and what Jared Diamond termed "The Great Leap Forward" some 40,000 years ago when humans made significant advances in tools, weapons, and culture that left strong traces in the archeological record? and then, of course, steps towards farming and complex village life after the last ice age, 13,000 years ago?

would seem a nice intersection of genetic and archeological evidence of changes in the human brain that led to changes in human culture.

Harald Korneliussen · 15 September 2005

'Rev Dr' Lenny Flank wrote: "Resistance to disease? All you need to dominate the world is a better military than they've got."

No, I think if you compare the death rates from war to the death rates from disease, disease will win for all parts of human history, AFAIK. [It's no use killing your wimpy little pacifist neighbor tribe if the diseases you got from splashing their blood about devastates your tribe.]