Is human evolution accelerating?

by on December 10, 2007 at 9:38 pm in Science | Permalink

This paper says yes, over the last 40,000 years.  The basic mechanism is that more people result in more adaptive mutations, plus environments have changed rapidly, due largely to technology and culture.  Here is an LA Times summary, it claims that the pace of human evolution has accelerated hundredfold [sic] since the invention of agriculture (some reports indicate "ten to hundredfold").

How about this summary:

Prof Hawks says: "We are more different genetically from people living 5,000 years ago than they were different from Neanderthals."

As far as I can tell this looks legitimate.  Here are one hundred different news summaries, here is Scientific American.

Thanks to several loyal MR readers for the pointer.

Addendum: Read this for explanation, it gets even more interesting toward the end, another implication is that viruses are more dangerous than we used to think.

razib December 10, 2007 at 9:54 pm

i have some tedious exposition of the theoretical background. p-ter of gnxp.com will have some critiques of the tests for selection they used in terms of the biases that creep in. i think john’s point about time as a major dimension of variation is something people need to think about more (though MR readers who have read greg clark should be familiar with the general principle).

razib December 10, 2007 at 10:31 pm

But wouldn’t technology advances reduce the survival importance of mutations?

don’t think of it is something like ‘survival.’ thing of a mutation as a potential deviation from population mean fitness. one could argue that domestication of cattle was a technology. the result was the survival benefit of a dominant gain of function mutation on the LCT locus which conferred adult persistence of the lactase enzyme. this LCT persistence allele went from 0 to 95% frequency in northern europe within the past 6,000 years (and also spread to much of western eurasia and north africa). the selection coefficients are on the order of 10%, that means a 10% increase in fitness relative to the population mean.

So while there might be more variations, I wonder whether there might be more “survivalibity” as well.

you need to unpack this “survivability.” for the vast majority of our species’ existence we’ve been in a malthusian trap. in any case, death rates or longevity isn’t relevant to evolution. for adaptive evolution you need a correlation between reproduction and a particular genotype and variance of that reproduction. many evolutionary models assume a poisson distribution of reproductive variance, but the reality is that the variance is probably greater than that, and, agriculture and the rise of neolithic mass societies might have increased male variance A LOT, which would crank up adaptive evolution. think of the “genghis khan” haplotype.

just because we are living in a relatively safe world with antibiotics doesn’t mean that selection isn’t salient. all you need is for phenotypic variation to track reproductive variation, for the phenotypes to be heritable.

snark December 10, 2007 at 11:59 pm

“We are more different genetically from people living 5,000 years ago than they were different from Neanderthals.”

Sounds much less controversial than this nearly equivalent form: “We [well, most of us, and probably everybody reading this] are more different genetically from people descended from those who took up agriculture only within the last millenia than they are different from Neanderthals.” For example many Africans and Native Americans.

Vish December 11, 2007 at 12:16 am

The paper may well be legitimate. But its worth noting that these are all ex multi-regionalists (those who believed that humans in different regions evolved pretty much independently for millions of years), who would love to have large amounts of genetic differences between “primitive” africans and the better races. Unfortunately for them, classic multi-regionalism is dead, but how convenient that they appear to have found other mechanisms of rapid evolution.

razib December 11, 2007 at 12:34 am

john comes out of multi-regionalism. i don’t know if henry was too involved in this debates, though it wouldn’t surprise me if he was a multi-regionalist, but a generation ago most physical anthropologists were multi-regionalists. the other authors are too young or out of the field. and as i said, you’re attempt to cast aspersions based on associations with multi-regionalism don’t make any sense, it emphasis pan-species phyletic gradualism.

razib December 11, 2007 at 1:03 am

“Have you noticed in nature vs. nurture debates, how often the nurture side rushes to play the guilt-by-association card?”

sure, but my point is that that doesn’t even apply here! both multi-regionalists and out-of-africanists try to pull the PC-card. but ultimately they’re models of human evolution that don’t apply that much to current political debates. i mean, vincent sarich was one of the early researchers who work directly led to the out-of-africa molecular model, and he’s a race realist. are we going to hold that against out-of-africa?

Floccina December 11, 2007 at 9:55 am

The interesting question is what direction is going in, maybe prettier girls and taller boys? Who is reproducing and who is not? It seems to me that today as far as among the children of the middle class, people with middleclass values, homely girls and unsuccessful boys are more likely than in the past to never marry and to never reproduce.

While pessimist like to point out that less successful people are having more children than the very successful, it is my guess that the least successful are also not reproducing very much. Some homeless people may have passed their genes on but I would guess that most have not. Mentally retarded generally do not reproduce. Very unattractive people seem to reproduce at a lower rate. Also to the pessimist good looks and male height do correlate positively with intelligence and overall health.

Mennonites are still reproducing at a high rate at what point do they become a significant percent of the population. Religious people in general might be reproducing faster than non-religious people.

Recently people who like children, and this could be genetic, are reproducing far more than others. The cheaper by the dozen type of family where both parents love children are way out of the norm today but still exist if they pass on this desire for large families on to their children they could become a significant force. Also, an interesting thing are these sperm and egg banks that buy Harvard students sperm could begin an interesting trend.

There are lots of trends and with some people out producing others by huge margins it is hard to predict what direction things will go in 50 to 100 years.

sourcreamus December 11, 2007 at 11:51 am

Does this paper or any other deal with how humans have evolved? I have read that we are smarter, taller, and can drink cows milk, but is there anything else that would seperate us from people 5,000 years ago?

Mark December 11, 2007 at 2:15 pm

Chris, by definition the ones with ‘better’ genes have more children. Otherwise they would be having fewer and thus be evolutionary inferior :)

TGGP December 12, 2007 at 2:52 pm

M1EK, there is still selection for those who have more children. The genes of those that reproduce less will be swamped by those that do more.

kev December 13, 2007 at 4:03 pm

I am not a biologist, but I read through this discussion with interest, and wondered how long it would take before a ‘crusader’ would come along and introduce god. Apparently only 2 days. Perhaps the approaching celebration of Mithra (renamed to Christmas by emperor Constantine in 313 CE), will keep them busy and post any more nonsense.

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