December 10, 2007
Cochran And Harpending See Human Evolution Acceleration

Evolutionary theorist Greg Cochran and genetic anthropologist Henry Harpending have teamed up again and with John Hawks, Eric Wang, and Robert Moyzis to argue that human evolution has greatly accelerated in the last 10,000 years and the human race is diverging.

Dec. 10, 2007 - Researchers discovered genetic evidence that human evolution is speeding up - and has not halted or proceeded at a constant rate, as had been thought - indicating that humans on different continents are becoming increasingly different.
 
"We used a new genomic technology to show that humans are evolving rapidly, and that the pace of change has accelerated a lot in the last 40,000 years, especially since the end of the Ice Age roughly 10,000 years ago," says research team leader Henry Harpending, a distinguished professor of anthropology at the University of Utah.
 
Harpending says there are provocative implications from the study, published online Monday, Dec. 10 in the journal Proceedings of the National Academy of Sciences:

  • "We aren't the same as people even 1,000 or 2,000 years ago," he says, which may explain, for example, part of the difference between Viking invaders and their peaceful Swedish descendants. "The dogma has been these are cultural fluctuations, but almost any Temperament trait you look at is under strong genetic influence."

  • "Human races are evolving away from each other," Harpending says. "Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity." He says that is happening because humans dispersed from Africa to other regions 40,000 years ago, "and there has not been much flow of genes between the regions since then." 

"Our study denies the widely held assumption or belief that modern humans [those who widely adopted advanced tools and art] appeared 40,000 years ago, have not changed since and that we are all pretty much the same. We show that humans are changing relatively rapidly on a scale of centuries to millennia, and that these changes are different in different continental groups."
 
The increase in human population from millions to billions in the last 10,000 years accelerated the rate of evolution because "we were in new environments to which we needed to adapt," Harpending adds. "And with a larger population, more mutations occurred."
 
Study co-author Gregory M. Cochran says: "History looks more and more like a science fiction novel in which mutants repeatedly arose and displaced normal humans - sometimes quietly, by surviving starvation and disease better, sometimes as a conquering horde. And we are those mutants."
 
Harpending conducted the study with Cochran, a New Mexico physicist, self-taught evolutionary biologist and adjunct professor of anthropology at the University of Utah; anthropologist John Hawks, a former Utah postdoctoral researcher now at the University of Wisconsin, Madison; geneticist Eric Wang of Affymetrix, Inc. in Santa Clara, Calif.; and biochemist Robert Moyzis of the University of California, Irvine.

Using data from the International Haplotype Map Project on single nucleotide polymorphisms (SNPs which are single letter genetic differences)

Harpending and colleagues used a computer to scan the data for chromosome segments that had identical SNP patterns and thus had not broken and recombined, meaning they evolved recently. They also calculated how recently the genes evolved. A key finding: 7 percent of human genes are undergoing rapid, recent evolution.

So we are becoming less alike due to adaptations to local environments. My guess is this trend will accelerate when offspring genetic engineering becomes possible. People in different cultures, religions, climates, occupations, social classes, and regulatory environments will make different decisions on which genetic variations to give their offspring. As a result groups will become less alike. Some groups will choose genes that enhance analytical ability and mathematical skills. Some will emphasize genes that boost ambition and perhaps even ruthlessness. Others will go for genetic variations that increase moral motivation and spirituality.

Update: The divergence of human genomes is a result of growing human populations moving into lots of different habitats that each exert different selective pressures. The selective pressures operated on immune systems, musculature, hair, skin, brains, and many other aspects of human shape and physiology.

It says something about the adaptive value of specific temperaments to specific habitats that these researchers report big selective pressures on genes that control temperament. That makes sense if you think about it intuitively. A hunter probably needs a different temperament than a goat herder (who experiences a lot of solitude) who needs a different temperament than a merchant (who interacts with many other humans and needs to enjoy sizing them up quickly). Some tasks are far more cognitively demanding than others. Some tasks require much more hand-eye coordination or better balance or more strength or endurance. Humans working at different tasks to survive in different environments got selected to be shorter or taller, better sprinters or better long distance runners, more muscular or fatty or skinny, and many other attributes. This is akin to specialization of labor.

See the John Hawks introduction to the paper on his blog. Also see his "Acceleration rarely asked questions" about the research. Hawks says the selective pressures acting on human genomes have been so strong in recent history that the signal they are measuring is larger than the biases one might expect would make the data hard to interpret.

In the earliest studies, when people were finding that 3 or 4 percent of a sample of genes had signs of recent selection, those numbers were already extremely high. They got even higher, as more and more powerful methods of detecting selection came online. Our current estimate is the highest yet, but even this very high number is perfectly consistent with theoretical predictions coming from human population numbers.

At one level, the mathematical answer is as simple as "more people means more mutations." But more deeply, we can predict a linear response of new selected alleles to population size, and we can model this response with respect to a particular frequency range. The genome is a complicated place -- with different mutations originating at different times, selected at different strengths, consequently with different fixation probabilities and different current frequencies. For some reason, nobody really tried to describe this mathematically before.

Now, our model is extremely simple -- it can be challenged on several specific bases. For instance, population increase was not a simple exponential -- it grew in fits and starts, with some significant crashes. The average strength of selected mutations probably changed over time, and the distribution of the strength of selection may have departed from our assumptions. Even the adaptive mutation rate may have changed over time.

Still, the general prediction is quite clear: the population has grown, its conditions of existence have changed, and as a result selection on new mutations should have accelerated. And the observed data fit our theoretical prediction exceptionally well. Certainly we could do better if we made a more detailed model, and we will be doing some of that in future papers. But mathematical simplicity has a great virtue: we can see precisely why human historical changes should have accelerated this aspect of our evolution, and we can see the magnitude of the response. That magnitude greatly outweighs all potential biases.

Go read the full Hawks post. It is all worth reading.

Razib discusses the research and surveys the media reaction to this important report.

March 2009 Update: This work has since become the basis for an excellent book by Cochran and Harpending entitled The 10,000 Year Explosion: How Civilization Accelerated Human Evolution.

Share |      Randall Parker, 2007 December 10 10:34 PM  Trends, Human Evolution


Comments
K said at December 11, 2007 12:18 AM:

Randall. I think your last paragraph is essentially correct. Given the choice people will craft themselves and their children to have certain characteristics. And science seems about to supply options. The question is whether the choices will be made by the person or by the society.

It seems pretty clear that at first only the rich will have the means. They already do in some ways. But later, as the procedures become economically available to all, there will be social and government pressures on the individual to make the 'right choices.'

Melvin said at December 11, 2007 3:47 AM:

The authors pointed to high illegitimacy rates from "hit and run" fathers as one shaper of human evolution. African illegitimacy is very high. Matriarchal families are common among Africans for that reason. High violent crime rates in certain populations also. A dysgenic trend for such groups.

Mats-Erik Pistol said at December 11, 2007 5:10 AM:

Of course evolution is accelerating. Humans have never been in a more odd environment than now, and even the introduction of agriculture was a big shock to the genes. Presently the only pressure is to get as many children as possible. The earth is productive enough that almost nobody dies from starvation or predators. This will change though when the affluent population doubles or so, which is happening as we speak, due to the economic progress in Asia. Wheat, soy and corn prices have about doubled in the last year and this trend will continue until starvation sets in, within less than a decade (unless peak oil gives us a strong recession).
Why humans should diverge I am a loss to understand. Travel has never been easier and etnic dating is hugely popular. 30+ % of Mississippis population is descending from Africa. South Africa is full of former Europeans and Chinese students are taking over every university we have on this Earth. No, there will be no divergence but an extremely interesting situation when selection pressure turns away from having as many children as possible to having as many children that do not die early takes over. In addition pressure to not die in reproductive age will also raise its ugly face again, making the hunt for money a life and death game. Presently the only motif for earning money is to impress the neighbors and to find young attractive mates. When food takes 90% of a normal persons wage the situation changes dramatically, especially if food prices are volatile. Starvation WILL happen in the near future. It is a popular notion that the human population will soon stagnate since affluent woman chooses not to have children. Those affluent women that do get many children will soon take over the world and overpopulation occurs. It may take a few hundred years which still is a blink in history. Starvation will in practice happens sooner since so many asians also want to eat meat and they are getting the means to buy it. It may be that conscious selection of genes in offspring will become a major driving force in evolution but I think shere fight for survival will be stronger.

cathy said at December 11, 2007 5:19 AM:

1) John Hawk's blog has more detail - he promises a FAQ tomorrow at http://johnhawks.net/weblog/
2) I hate it when scientists talk about 'race' because most Americans think race means skin color.
3) I wonder about genetic evolution being the reason that Swedes are currently less warlike than their ancestors. Sweden is not isolated and the Vikings travelled pretty widely - maybe only the peaceful ones stayed home, while the warlike were spreading their genes in Ireland.
4) I also wonder if this gives a genetic advantage to countries that welcome immigrants - we have a lot of genetic material to work with.

Anders Sandberg said at December 11, 2007 6:10 AM:

The timescale of technological genetic change is on the order of a generation (plus the time for getting safety testing, regulatory approval and parental interest). But the timescale of many forms of technological change is faster. This is likely to make most genetic enhancements obsolete by the time the embryo has grown to an adult - "thanks mom and dad for the life extension and ambition genes. Too bad we can do that even better with nanomedicine and computer aided personalities these days." Also, the kids of the rich will find themselves surrounded by slightly younger, slightly more enhanced peers.

Altogether, this means that the genetic divergence may be smaller than the technological divergence. The descendants of Facebooking social software people might be far more different from the descendants of the augmented reality people, simply because they have grown up in a particular media culture and chosen enhancements accordingly.

As for Swedish warlikeness: there has probably been some selection against ambition and aggression through migration (both during the Viking era, during Sweden's time as a major power and during the migration to the US in the 19th century), but since this just skims the gene pool it would be unlikely to have had a huge effect at home. I think cultural explanations might work much better here. Culture can change surprisingly fast too.

Wolf-Dog said at December 11, 2007 6:15 AM:

But within less than 20 years modern genetics might revolutionize food production in such a way that factories would create the necessary nutrients without the need for vast farm lands, etc. So just as science is quickly responding to the coming shortage of oil, once the fear of starvation starts, all the universities will start focusing on food production.

Paul F. Dietz said at December 11, 2007 6:44 AM:

The notion that modern civilization has stopped human evolution has never made sense to me. Huge changes in the environment we live in should radically shift the genetic optimum, and that's just what these guys see evidence for.

One long term implication of this is for human population growth. Advanced countries have low birth rates, but eventually that will be selected against. Future humans will have large families even in high tech cultures, if they are allowed to.

Mats-Erik Pistol said at December 11, 2007 10:29 AM:

Anders,
"The timescale of technological genetic change is on the order of a generation" is almost obsolete by now. There is at least one company intending to change (rewrite) existing genes in a body already. They intend to use zinc-finger protein technology. People working in gene synthesis are talking about chromosome synthesis although we are some time away from that, being able to synthesize only kbase-pairs today within reasonable cost. Technology is changing so fast that our Earth is a very unstable system indeed now. I fear that the reason we are the only intelligent species in the visible Universe could be due to a fact that intelligent species selfdestruct one way or another. For us it seems that climate destruction will be the cause of selfdestruction.
Wolf-dog. It does not matter if food production goes up a factor of ten. Population growth will continue until negative feedback, called early death, sets in. Only strong dictatorship over essentially infinite time periods can stop population growth. Even in this case, there will strong selection for genes that cheat the dictator in all possible ways such as expanding out in the far reaches of the solar system (or outside) to reproduce.
The skimmed Swedish and Norwegian populations went to Iceland. Icelandic people are not very aggressive supporting culture being the reason for peacefulness. Icelandic people have a high IQ supporting the notion that high IQ travels (which is known from other studies). There are few countries (Armenia) with such a high concentration of GMs and IMs in chess as Iceland. Presumably the vikings liked chess.

David Govett said at December 11, 2007 1:09 PM:

Designer babies. Auto-modifiable genetic code. Instantly adaptable immune systems. Gazillions of new animals, plants, bacteria, viruses. These are only a few of the powers humans will have in the coming decades. The Singularity will change everything.

Mthson said at December 11, 2007 1:50 PM:

Scandinavia sending abroad the most aggressive 25% or whatever proportion of their male population for 200 or 250 years is bound to have a large effect on gene frequencies. Interest in personal combat and conquering tends to correlate with right-of-center views more than left-of-center views, so we'd expect a large shift to the left in those societies.

Iceland developed slowly because of a lack of interest from the home countries, and interest in homesteading on a backwater island is not the same as interest in raiding and conquering, so differential selection for migration to Iceland compared to military raids South and East seems plausible.

Pete said at December 11, 2007 2:31 PM:

Wouldn't this undermine the principle of human equality, and potentially justify racism and discrimination? Some critics have questioned the quality of the science, and think culture plays a bigger role than genetics. Genes get passed on to offspring, but that doesn't necessarily mean we're evolving as people did tens of thousands of years ago.

Technically all humans came from Africa, we just used our minds to adapt differently. There could be other factors in why the Vikings became so peaceful? Perhaps the spread of Christianity to Scandinavia may have made them feel part of a greater European culture, and desire less to attack their neighbours. Not to mention the Christian ideals of love for neighbour, and human equality. I've heard hunger was one cause for their invasions. A culture of violence may have spread in Scandinavia, justifying their invasions to them.

Look at people in the "ghettos" in American cities. Violence is constantly reinforced, in music and such, and that's all many of them see.

Plus, we don't live in a culture anymore where "the strong survive." We have social justice, public hospitals and stuff - so wouldn't that actually decrease the need to adapt and evolve? I'm not entirely discounting genetics. I just agree with the critics, that perhaps it doesn't play as much of a role as Harpending and Cochran make it out to.

Aaron said at December 11, 2007 6:05 PM:

The Scandanavians did NOT become peaceful with Christianity- they just stopped raiding outside. Sweden was a VERY agressive power until Charles the 12th met Peter the Great of Russia. Many more generations of losing people in war.

Paul F. Dietz said at December 11, 2007 6:32 PM:

Wouldn't this undermine the principle of human equality, and potentially justify racism and discrimination?

Whether it does or not has nothing to do with whether the theory is correct. To infer correctness from desirability, or incorrectness from undesirability, is a fallacy of wishful thinking.

Genes get passed on to offspring, but that doesn't necessarily mean we're evolving as people did tens of thousands of years ago.

Of course we aren't evolving as people did 10Ks of years ago. We evolving much faster now, as our environment diverges faster and faster from what our genomes were equilibrated toward.

This sort of rapidly accelerating evolution is also likely happening in many other high-population species in environments we've highly perturbed.

Mthson said at December 11, 2007 7:21 PM:

Human equality isn't dependent on physical identicality. People can be short or tall etc. or different in any number of aesthetic or functional ways, but we still afford them the same human dignity. The danger of letting this topic be treated as a moral question instead of a empirical question has historically been (over the last four decades) that it tends to make us say things that are true in a moral sense but not quite true in an empirical sense.

The main evolutionary trend occurring today in most countries seems to be for lower socioeconomic groups and religious groups to have more children, both through quantity and through shorter generational cycles.

Barry P said at December 11, 2007 11:23 PM:

The usa is historically and continues to be a land of immigrants -- legal & illegal--. Contrary to must assumptions, those who immigrate are more aggressive and energetic persons. Their offspring are going to show those traits in varying degrees. It is a select group that now expands in a more favorable environment - the USA or modern Europe.

In contrast the established population tends to have less children as socio-economic position increases. The rich & successful typically have less children than poorer people. The average genetic stock in effect doesn't increase.

It appears to be a wave phenomena, with initial advances in quality and quantity by the emigrees, and stagnation or dropping of average once they become established population.

Are we destined to have a superior wave of emigrees followed by another as the predecessors lose their genetic/reproductive drive?

Randall Parker said at December 12, 2007 6:15 PM:

Mats-Erik Pistol,

I think you make an incorrect assumption: That groups living close to each other will intermarry. Well, sometimes. But not always. For example, the Syrian Jews in Brooklyn have such harsh prohibitions against intermarriage (they end all relations with their children who marry outside of their community) that they rarely do it. Also, the black-white intermarriage rate in the United States is pretty low.

Also, I see a different kind of segregation coming in the future based on brain alleles, and for more than just intelligence. We already have people of similar temperaments being more likely to marry and to stay married. In fact, people who marry across racial boundaries are more similar to each other in temperament than people who marry within their races (sorry, that's from memory and I don't have a handy cite for that). What I foresee is a big shift toward mating between people with similar personalities and moral tendencies and for those people to have kids who are more like them.

There will be less mental differences between parents and offspring since parents will have greater control over which of their genes they pass to their offspring. In fact, parents will make their kids possess the same traits they have but even stronger doses. Masculine guys will genetically engineer their sons to be even more masculine. Glib salesmen will assure their kids are even better with the gift of gab and that they are good at reading the personalities of others. Whereas some Aspies (people who have Asperger's Syndrome) might even decide that being an Aspie is so superior (and some do not see their condition as a disability) that they kids should be Aspies too. Already there are deaf people who are trying to have deaf offspring.

mats-erik Pistol said at December 13, 2007 4:58 AM:

Randall,

You are right that some religious groups very seldomly intermarry and they can become a segregated group if they can keep their culture long enough. Amish is another example. Even in the Amish there is genetic import since Amish sometimes adopt children from the outside. A few amish leave the group and export genes. Also in the closed hasidic groups we have the phenomenon of infidelity where women get pregnant with outside men and hasidic men (maybe working on Wall street with a high income) have lovers in the gentile world. It is not common but it happens (I forgot the reference). I think this is enough that isolated groups forming a new species will not occur. It is also highly unlikely that religious groups will keep their isolation when starvation sets in again.
That new groups will form based on gene selection in offspring is intriguing but not likely. Society is changing too fast. Door-to-door salesmen will not form a special class of people since we will buy everything from the internet soon.
I guess I understood divergence as the formation of special groups that more and more become almost a separate species. This will not happen since groups are not selected for by evolution. Only genes are selected for with some modulation since the genes live by necessity in a body and have to share their lives with other genes. No, the divergence that will occur should be rephrased to say that the diversity of the gene pool will increase dramatically in the future. This will as stated repeatedly above be caused by artificial selection/creation of genes in offspring in addition to more standard means. Then at the singularity everything breaks down. I wonder if it is an essential singularity or a removable one? Integrable?

Dave Gore said at December 13, 2007 1:59 PM:

20% of the people in each generation leave no genes behind (see http://www.ancestry.com/learn/library/article.aspx?article=5921). Is it a surprise that evolution is progressing so rapidly?

Mthson said at December 13, 2007 2:47 PM:

Here's the working link: http://www.ancestry.com/learn/library/article.aspx?article=5921.

"The number of ancestors common to all Europeans today increased, until, about a thousand years ago, a peculiar situation prevailed: 20 percent of the adult Europeans alive in 1000 would turn out to be the ancestors of no one living today (that is, they had no children or all their descendants eventually died childless); each of the remaining 80 percent would turn out to be a direct ancestor of every European living today."

Randall Parker said at December 13, 2007 9:40 PM:

Mats-Erik,

Again, I think people will split apart based on genetically caused cognitive differences. I believe different people will give their kids different innate methods for moral reasoning. These difference will cause such large differences in values that it'll be hard for these morally different people to co-exist in the same society. So they will segregate.

I expect we will discover genetic causes for:

- altruism, both the extent of it and the targets for altruistic behavior.
- jealousy, sexual, for possessions, for status, and other.
- empathy.
- ease of angering and triggers for angering.
- lustfulness.
- what types of physical appearances are attractive
- and many other esthetic reactions, emotional reactions, and behaviors.
- monogamy/promiscuity.

Once people can control some of these attributes in offspring people will make different choices as to the extent and shape of various cognitive attributes they will give to their kids. I predict that they will make incompatible choices.

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