Galloping human evolution

Time was, teachers used to tell their students that accelerating cultural evolution – the alphabet, the wheel, movable type, the steam engine, the computer, whatever – meant human biological evolution wasn’t important any more. It was too slow.

A blockbuster paper published online today by the Proceedings of the National Academy of Sciences turns that old story on its head.

Cultural evolution diversifies the physical environments where humans live, creating a multitude of places where useful mutations can thrive. And greatly increased population density means ever more bodies where mutations may be selected for usefulness.

The result, says Greg Cochran, one of the authors, is that human biological evolution has accelerated, to perhaps 100 times as fast as in prehistory. (And that’s before we had the genetic tools to modify it on purpose.)

I don’t intend to dismiss the other authors; it’s only that Cochran happens to be the one I talked with. The others are John Hawks, Eric T. Wang, Henry C. Harpending, and Robert K. Moyzis. I’ll add a link to the specific article at PNAS as soon as I have one.

UPDATE: Steve Sailer at http://isteve.blogspot.com/ links to the paper at

http://www.anthro.utah.edu/PDFs/accel.pnas.smallpdf.pdf

and also has links to early press coverage at the LA Times, Reuters and elsewhere

Also, lead author John Hawks has further comment about the study on his blog,

http://johnhawks.net/weblog/topics/evolution/selection/acceleration_embargo_ends_2007.html

The old story was that around the time agriculture started to replace hunting and gathering as a way of life for human beings, biological evolution faded into insignificance because it was so much slower. There’s hardly been enough time – only about 10,000 years or so – for human biology to have changed enough so’s you’d notice.

Not so, as studies of the human genome are demonstrating. When people began domesticating animals, planting crops, and living in settled communities, they created environments for themselves quite different from any environments the human species had occupied before, and natural selection proceeded, as it always does, to favor survival and reproductive success for individuals who were, by chance, better adapted to those environments.

The marquee example is retaining the ability to digest milk into adulthood, which is nearly universal among people of European descent, and quite rare elsewhere.

But the shift to agriculture was also important, Cochran said, because agriculture can support a larger population. Any individual might be the next one to draw a winning ticket in the genetic lottery, and the human species was suddenly buying a lot more lottery tickets.

Think of the genes as a crew of thousands of extras, swarming around the sets and the studio lots, auditioning for jobs. They play more than one role, in lots of different movies, for different directors, as circumstances permit.

One day on the set where they’re filming a swords-and-circuses epic, the director spots a spear-carrier who has given an especially elegant performance, impaling a charioteer.

“You there, with the spear? Could you do that again? Yeah?! I’m gonna make you a star!” And – for a quick glimpse into how biology and culture drive each other – if the spear-carrier proves to be bankable, he’ll get more roles, the director will get more movies, the studio will tilt toward making more epics and the extras with good spear-carrying traits will be more likely to succeed in that environment.

Success, in the gene world, is reproductive success – leaving descendants – but given the role of the casting couch in Hollywood, maybe that’s not pushing the metaphor too far.

On the next set over, the director is casting a chick flick. He says to his assistant, “see that looker over there, the one with the purple eyes? Ask her whether she can ride a horse.”

Now the aspiring starlets competing with Elizabeth Taylor for a role in “National Velvet” can take riding lessons. But they can’t do anything to give themselves violet eyes.

The hunter-gatherers competing with pastoralists for food resources could certainly have learned to keep domesticated animals. But if they and their children could not digest milk much past the average age of weaning, it wouldn’t do them any good. In hard times they’d starve while the meek drinkers of milk inherit the earth.

Or at least a broad swath of it from Iceland to South India.

Accelerated biological evolution in humans doesn’t mean that we’re turning into aliens, but there is evidence that hundreds of human genes are under selection pressure, having to do with such things as diet, vitamin metabolism, the functioning of the central nervous system, disease resistance, hair, skin and eye color, the shape of the skeleton and behavioral traits better suited to living in large groups. “We’re tamer,” Cochran said.

I asked him why we’re not developing floppy ears like the silver foxes bred for tameness.

So where is that evidence coming from? In part, from an ambitious international effort called The HapMap Project (www.hapmap.org).

The human genome has about 3 billion base pairs, strung out in long chains in 23 pairs of chromosomes. Between any two people, most of the base pairs will be the same, but researchers estimate there may be some 10 million locations along the chromosomes where variant spellings of the genetic code appear. If you should happen to hear geneticists talking about “snips,” that’s what they mean; it’s short for “single nucleotide polymorphism.”

The HapMap project is intended to make that vast amount of information more manageable so medical researchers can more efficiently go looking for genes that may influence health. “Genetic variants that are near each other tend to be inherited together,” the HapMap site explains. “These regions of linked variants are known as haplotypes” (hence the name).

A relatively small number of “tag” SNPs is enough to uniquely identify a haplotype, and if researchers know what those are, they don’t need to look at every base pair.

Because chromosomes are typically cut apart into several pieces and reassembled during reproduction, it is approximately correct that the longer a haplotype is, the younger it is. So the HapMap serves as a genetic clock for the species.

The ability to digest lactose goes back roughly 8,000 years. Hey, useful mutations don’t always come along just when you want them. Malaria resistance begins to appear about 5,000 years ago.

Most haplotypes are old, and found in almost every human population, though not necessarily with the same frequency. But the clocks in different places started at different times and they’re not all running at the same speed. The HapMap project is studying three groups of 90 people each, one from the Yoruba tribe in Nigeria, one from East Asia (Tokyo and Beijing) and one of Americans of northern European descent. All the groups have numerous genes under selection, but not all the same ones. If the evolutionary price of resistance to malaria is sickle-cell anemia, it is far too high a price to pay for populations living where it’s too cold for malarial mosquitoes anyway. If the evolutionary price of light skin is melanoma, the price is too high in equatorial Africa.

You understand there is no agency or designer deciding these things. There’s just a small statistical advantage in each generation for those with a more favorable version of a gene, “favorable” meaning only that children in that environment who inherit it are slightly more likely to grow up and have children themselves than those who don’t. Researchers might not even know which gene in a haplotype is being selected for, or what it does.

They do know, though, that it’s happening faster than we used to think. Cochran said, according to a press release from the University of Utah, “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.”

About linsee

Linda Seebach retired in 2007 from the Rocky Mountain News in Denver, where she was an editorial writer and columnist.
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25 Responses to Galloping human evolution

  1. Byron says:

    The argument is not, as far as I know, that cultural adaptation replaced biological evolution because biological evolution was “too slow;” it was because cultural adaptation reduced the selection pressures that resulted in differential rates of reproduction. Once you have insulin therapies, for example, diabetes becomes a much smaller cause of differential reproduction. Ditto corrective lenses and bad vision. Etc.

  2. Thomas Collins says:

    In the article it is stated that:

    “You understand there is no agency or designer deciding these things.”

    Fascinating. Experimental scientists can describe experiments they claim to have designed, but the unwashed masses must understand that there could be no level of intelligence in the universe that could have designed the genetic code to act in a way that we observe as a process we call evolution.

    Far closer to the truth, however, is that the most an evolutionary biologist can say at the moment is that a controlled experiment cannot be developed under current knowledge to determine if the phenomena we observe at our level of existence is the result of a creative act that humans at our level might describe as a higher intelligence. Discussion about such matters may still be important, however, because today experimental science covers just a portion of matters about which humans appear to have a natural wonder.

    It is always amusing to me to see evolutionary biologists speak in ways similar to the above quotation. Even simply within the sphere of experimental science, evolutionary biology doesn’t have a high level of mathematical precision. Perhaps evolutionary biologists feel themselves under siege from those claiming the authority of God for their view of how humans developed, but that is no excuse to hide in the cocoon of pseudo-scientific thought that would justify making a statement such as the one quoted above.

  3. Jim says:

    I would like someone show me a human mutation that was/is actually useful. Mutations are not good and they die. They never, if indeed exist, ever produce good. All living things have been and will continue to created by GOD and nothing else. Please have a Merry Christmas and try to learn what Christmas is all about.

  4. Tom Holsinger says:

    Jim,

    Be sure to enjoy the ice cream on your Christmas pie.

  5. Brock says:

    EPE = MPP*NI*SP

    Evolutions Per Epoch(EPE) = Mutations Per Person * Number of Individuals/Population Size * Strength of Selective Pressures

    To summarize your article: EPE’s gone up because we’ve increased two of its three variables (a lot); MPP isn’t the one that one that went up.

    But for successful mutations to spread, they must be allowed to breed. Are Mormons evolving faster than the Chinese?

  6. Brock says:

    Thomas Collins:

    Be sure to check out the post immediately previous to this one. It discusses one example of “the ability to discover support for what one already believes amid a mountain of overwhelmingly contrary evidence.”

  7. Dale Amon says:

    Fascinating. I’ve read other papers on Vitamin D metabolism and skin color, and how many diseases have a North-South trend line (with additional dips for places with particularly small amounts of sunlight).

    There have also been some writings on genetic changes in the middle east just around the time of the first large human settlements and these may have been changes which led to a greater percentage of survival in that new niche environment.

    The speed of evolution has also been recently shown in the petri dish. Some scientists have managed, without any genome manipulations at all, just the use of pathogens, managed to almost generate a new species in very short order… the almost because they did not take it far enough for the new variant to be unable to produce offspring with the original stock.

    Things are moving very, very fast in this field!

  8. Fugate says:

    Let me get this straight. Human evolution is advancing at at exponential rate and all we’ve got to show for it is that some populations can tolerate lactose after 10,000 years of selective breeding. Rather anemic.

    I wonder if this is even “evolution” at all. Isn’t it just gene selection rather than a mutation?

  9. John Hawks says:

    Thanks for the post. I’m the lead author, and you can find some more details about the study on my blog:

    http://johnhawks.net/weblog/topics/evolution/selection/acceleration_embargo_ends_2007.html

    The commenter that noted how fast things are moving couldn’t be more right — this is stuff that we couldn’t have imagined five years ago!

  10. Accelerating mutation rate, eh? So when should we expect the X-Men? ;)

  11. M. Simon says:

    Bad Vision is not necessarily bad.

    It adapts one to fine close in work. The kind of work that might keep one out of wars. Making chain mail for instance.

  12. mrsizer says:

    Tom, no one (in this thread) is saying that God did not create the knobs, merely that It does not turn them.

    One of the most difficult things in the science of evolution is not being forward-looking. Evolution is driven by what is useful at the time the change happens. There is nothing/no-one looking ahead and planning an evolutionary change now that will be useful in 1,000 years. That’s what is said above; no mention whatsoever of what put the process in motion in the first place.

    That, in fact, is one of Intelligent Design’s biggest arguments against evolution: Some things are too complicated to have been accomplished piece-by-piece over time. Unfortunately for that argument, “too complicated” almost always means “we just don’t know, yet”.

    I don’t want to turn my back on reality: These things exist and have happened over time, whether we like it or not (or God could have created the Universe yesterday and everything is a trick, but that’s a useless philosophy). I also don’t want my God to be a “God of the Gaps” who is only responsible for things that are “too complicated”, which is an ever-diminishing set.

    Even the real church – led by the apostolic successor of Peter – admits that evolution happens (and it took them 700 years to pardon Galileo).

    Understanding how God’s creation works is not incompatible with belief in God.

    There’s also no reason to doubt the Bible – but many reasons to distrust the accuracy of the details. Imagine yourself as the smartest scientist on the planet. You are the ultimate McGyver. You can build a fusion reactor with your bare hands, an iron meteorite, and a bronze spear. You are transported back in time 5,000 years and you explain, to the best of your incomparable ability, how the world works to the natives. They write it all down. Do you think that, given their world-view, that, now, given our world-view, we could do anything detailed based on their writings? Now think how much bigger the gap is between God’s knowledge-base and yours. Errors are inevitable.

    Besides, be nice.

    Merry Christmas,
    – Mark

  13. mrsizer says:

    John (just followed the link, but you don’t allow comments), in case you check back:

    LOL! I hope you don’t use the word “recent” when talking with the press. They are idiots and “recent” means “last week” not “since the dawn of agriculture”, which you will probably have to point out was 40,000 years ago since most of them know more about Britney Spears than history.

    Fascinating stuff. Congratulations (and Merry Christmas),
    -Mark

  14. pineybob says:

    Anyone who expresses utter confidence in purely material origins is just as big a fanatic as Jim is for his total faith in divine origins. Acceptance of natural selection does not necessarily require us to believe that the prime mover was not an intelligence. I have no difficulty believing that humans and chimpanzees are cousins, but I do have some doubts (as perhaps did Darwin) about the purely material origins of the Cambrian explosion. I have a great deal of difficulty believing that life and the complexity of the cosmos arose from nothing but gigantic quantities of hydrogen, time and improbability.

  15. r j sundberg says:

    Evolution is primarily driven by natural selection. “Natural Selection” is the forces in the natural world which favor the most adaptable individuals to breed new offspring over the less adaptable individuals through breeding success and mortality success. The advent of civilization some 8,000 years ago altered this formula so that the forces of nature no longer controlled this process. In other words, civilization drastically altered “Natural Selection” by eliminating the “Natural” and substituting the civilization quotient which includes many cultural factors that were never present in the “Natural Selection” method of selection. I have my own opinions about the consequences, but only want to draw this distinction to those who are discussing the subject.

  16. Berend de Boer says:

    Accelerated human evolution? It’s happening all around us, espcially on TV, just watch Heroes.

    Otherwise it would be helpful if authors distinguish between distribution and shuffling of existing genes and actual new functionality (yes, that would be pointy ears or green blood).

  17. phil says:

    I don’t see that human evolution is proceeding at a faster rate. Faster than what ?

    Experimental evidence indicates that roughly 25 generations is required for selection to spread a loci change throughout a small, cohesive population. Nothing discussed here changes or challenges these findings. So 25 human generations should approximately be 500 years (25 x 20 where 20 is an average reproductive age or age of 1st reproduction).

    All the larger human population and civilization does is increase the total diversity of the genome and the potential loci for selective pressure to act on, as I see it.

    Humans are animals like any other animal species on earth and like all life, any selective pressure is natural, be it human or whatever, its still natural selection. The artificial distinction between natural and human induced selective pressures are simply hubris.

    At any rate, I fail to see how basic mechanisms of propagation of genetic change have been impacted at all.

  18. Darwin says:

    “The hunter-gatherers competing with pastoralists for food resources could certainly have learned to keep domesticated animals. But if they and their children could not digest milk much past the average age of weaning, it wouldn’t do them any good.”

    Tribespeople in modern day Africa use their herds for much more than “milk” :

    a) butter (which is less than 1% lactose, and therefore digestable by all)
    b) meat
    c) blood (“milked” from the animals over the course of their lifetime via bloodletting)
    d) curds/cheese (many styles of which are digestable into adulthood)

    Is there something so fabulous about drinking raw liquid milk that it provides a significant advantage over these other uses of herd animals? I mean, sure, it’s a benefit, but compared to everything else herds provide.. seems pretty marginal.

    =darwin

  19. Tom Holsinger says:

    Phil,

    Check out Gregory Clark’s _A Farewell to Alms_ for fascinating evidence of an evolutionary psychology explanation of the Industrial Revolution.

  20. Clockmaker says:

    Readers who do not believe in evolution driven by random mutations and natural selection should refrain from commenting on this scientific article.

  21. Peterargus says:

    Mrsizer: Awesome post @ 7:41. You should write a book. Really.

    Darwin: Here’s something recent in the subject from http://news.bbc.co.uk/1/hi/health/6397001.stm :

    Dr Mark Thomas, from UCL, said: “The ability to drink milk is the most advantageous trait that’s evolved in Europeans in the recent past.

    “Although the benefits of milk tolerance are not fully understood, they probably include the advantage of a continuous supply compared with the ‘boom and bust’ of seasonal crops, its nourishing qualities, and the fact that, unlike stream water, it’s uncontaminated with parasites, making it safer.

  22. rosignol says:

    Is there something so fabulous about drinking raw liquid milk that it provides a significant advantage over these other uses of herd animals?

    1) relatively rich in nutrients and energy
    2) can be harvested without harm to the animal (unlike butchering, or even bleeding)
    3) does not require storage or preparation (unlike butter, cheese, etc)
    4) available year-round

    Interestingly enough, it’s also the kind of thing that wouldn’t have become an advantage until we started domesticating animals. So it’s conceivable that the mutation might have occurred at various points in human history, but died out for lack of usefulness.

  23. submandave says:

    This article raises again in me the frustration that the same term, “evolution,” is often freely used interchangably to mean both the process of natural selection that leand to refinement and improvement of a species as well as the radical mutations that, over eons, supposedly gives rise to biologic diversity and new species. The forces of the former are experientialy evident in our lives, yet that is often paraded as “scientific proof” of the latter.

    If the process of “evolution” as it referrs to natural selection has indeed accelerated then I would also contend that the absence of any accelerated diversity in the human species tends to counter the theory of “evolution” as primogenesis. I will again ask for a single example of any existing species for which a known mutation affecting the number of chromosomes (either additional or less) has produced a demonstrably improved and more viable state.

  24. Harry Springer says:

    I’m growing weary suggesting this over and over, with nobody realizing that it solves many dilemmas.

    Accept the atheistic evolutionary cosmos, under the standard theory.

    Accept a limited form of the Gaia notion, (that the biosphere adapts).

    Accept a limited inspiration from the Teilhardian notion of complexification as destiny.

    Reject the notion of intelligent design.

    It could well be that the growing interconnectedness is a time-reversed intelligent design.

    Mentality (the noosphere) is growing. Evolution is accellerating.

    Could the end point, be a loving singularity?

    It would explain why you can’t find God….

    He(She) didn’t get here yet!

    We didn’t become him(her) yet.

  25. I’ve tagged you with the “seven random things” meme here.