Monday, April 4, 2016

Farewell to Henry


Henry Harpending (1944-2016) died this past Sunday. He had a stroke a year ago, and then a second one three weeks ago, but apparently he died of a lung infection. This is one of the risks of getting older: you dodge one bullet only to get hit by another.

The cemeteries are full of people who die before their time, but this is one case where I really wish death had held off a while longer, so that he could see more of the fruits of his labors, particularly in the area of gene-culture coevolution.

No, he wasn’t the only academic to show that culture and genes have coevolved in our species. In fact, the idea probably originated with Claude Lévi-Strauss in the early 1970s:

When cultures specialize, they consolidate and favor other traits, like resistance to cold or heat for societies that have willingly or unwillingly had to adapt to extreme climates, like dispositions to aggressiveness or contemplation, like technical ingenuity, and so on. [...] each culture selects for genetic aptitudes that, via a feedback loop, influence the culture that had initially helped to strengthen them. (Lévi-Strauss, 1971)

This idea of gene-culture coevolution became popular in the 1980s through papers by L.L. Cavalli-Sforza, Robert Boyd, Peter Richerson, and Pierre van den Berghe. It then fell out of fashion because ... well, because. When Paul Ehrlich wrote Human Natures (2000), he returned to the conventional wisdom that cultural evolution had largely replaced genetic evolution in our species. As one became more important, the other became less so.

In 2007, Henry Harpending turned this thinking on its head with a study on changes to the human genome over the past 80,000 years. With four other researchers, he found that these changes actually sped up more than a hundred-fold some 10,000 years ago, when hunting and gathering gave way to farming, which in turn led to population growth and larger, more complex societies. Our ancestors were no longer adapting to relatively static natural environments but rather to faster-changing cultural ones of their own making. They created new ways of life, which in turn influenced who would survive and who wouldn't.

As Henry and his co-authors pointed out, this estimate of a hundred-fold acceleration is actually conservative:

It is sometimes claimed that the pace of human evolution should have slowed as cultural adaptation supplanted genetic adaptation. The high empirical number of recent adaptive variants would seem sufficient to refute this claim. It is important to note that the peak ages of new selected variants in our data do not reflect the highest intensity of selection, but merely our ability to detect selection. Due to the recent acceleration, many more new adaptive mutations should exist than have yet been ascertained, occurring at a faster and faster rate during historic times. (Hawks et al., 2007)

Few ideas belong solely to one person, but Henry deserves credit for perseverance. Most of the others, like L.L. Cavalli-Sforza, eventually found it expedient to focus on other ideas. Henry pushed on, not only by co-writing a book with Greg Cochran, but also by continuing to do original research.

I would like to say that Henry was allowed to work in peace. That's how things are in a free society, no? Unfortunately, he was repeatedly warned to stop, subtly at first and then not so subtly. Last year, the Southern Poverty Law Center added his name to its list of "extremists"—a list that, curiously, omits people whose skin is darker than peaches and cream.

In its "Extremist File" the SPLC describes him as follows:

Harpending is most famous for his book, co-authored with frequent collaborator Gregory Cochran, The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, which argues that humans are evolving at an accelerating rate, and that this began when the ancestors of modern Europeans and Asians left Africa. Harpending believes that this accelerated evolution is most visible in differences between racial groups, which he claims are growing more distinct and different from one another. The evolution of these racial differences are, in Harpending's account, the driving force behind all of modern human history. He is also a eugenicist who believes that medieval Europeans intuitively adopted eugenic policies, and that we should recognize the importance of eugenics in our own society. (Southern Poverty Law Center, 2015)
 
I would give that summary a D+.

- The book's argument was that genetic evolution slowly accelerated as modern humans spread outward from a relatively small area in Africa, beginning some 80,000 years ago. Much later, this acceleration greatly increased when farming began to replace hunting and gathering some 10,000 years ago. The actual Out of Africa event—when modern humans spread out of Africa some 50,000 years ago—was tangential to this process of accelerating genetic evolution, yet the SPLC summary makes it seem pivotal (perhaps to show that Henry was obsessed with black people?).

- The book's argument was that culture and genes coevolve: culture drives genetic evolution just as much as genes drive cultural evolution. And this process can take place within groups that are not normally thought to be “racial.”

- The last sentence is way off the mark. Yes, a culture will make it harder for some individuals to survive and reproduce, thereby removing certain predispositions and personality types from the gene pool, but this process is no more a "eugenic policy" than is natural selection itself. It's silly to use words like "eugenics" and "policy" for something that happens unconsciously in any culture, even in small bands of hunter-gatherers.

I don't mind people making unfounded criticisms. That's par for the course in academia. But was the SPLC interested in academic debate when it listed Henry as an "extremist"?

Indeed, what's the point of that list? Information gathering? Or is it more like incitement to extrajudicial punishment and, yes, extrajudicial violence? "Look folks, this is a BAD PERSON, so go and do what the justice system is too cowardly to do!" Isn't that the point of the exercise? And isn't that exactly what the KKK was condemned for doing?

A strange role reversal has taken place between the long-dead KKK and the SPLC. It's now the latter that tries to enforce its notions of good behavior through intimidation, veiled threats, public shaming, and blacklisting. It's now the SPLC that is conspiring, literally, to deny people their civil rights.

Anyway, Henry Harpending seemed unfazed by the SPLC's blacklisting. He was apparently one of those rare tenured professors who put his tenure to good use and blissfully went on doing what he had always been doing. I wish he had lived longer. He was irreplaceable not so much because he knew more but because he was unafraid to say and act on what he knew. I will miss him.

References

Cochran, G. and H. Harpending. (2010). The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, New York: Basic Books.

Ehrlich, P. (2000). Human Natures. Genes, Cultures, and the Human Prospect, Penguin. 

Harpending, H., and G. Cochran. (2002). In our genes, Proceedings of the National Academy of Sciences (USA), 99, 10-12.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC117504/  

Hawks, J., E.T. Wang, G.M. Cochran, H.C. Harpending, and R.K. Moyzis. (2007). Recent acceleration of human adaptive evolution. Proceedings of the National Academy of Sciences (USA), 104, 20753-20758.
http://harpending.humanevo.utah.edu/Documents/accel_pnas_submit.pdf 

Lévi-Strauss, C. (1971). Race et culture, conférence de Lévi-Strauss à L'UNESCO le 22 mars 1971
http://politproductions.com/sites/default/files/art-%C2%ABrace_et_culture%C2%BB_levi-strauss_unesco_22_3_1971.pdf  

Southern Poverty Law Center (2015). Henry Harpending, Extremist Files,
https://www.splcenter.org/fighting-hate/extremist-files/individual/henry-harpending

9 comments:

Ted said...

A nice tribute to a man who deserved it.

Dieter said...

Commenting on your December blog, whatever is happening in Europe now may well answer the age old question, how were the Neanderthals replaced. The theory that the brighter and more advanced smaller blacks from Africa just moved in does not wash, has never washed but the genetic research that has been done in the last few few years may just point to a more reasonable solution. The recent news that there far too little y chromosone can explain all that. The smaller blacks, fleeing either population or natural disaster come into contact with the larger, brainier Neanderthal who promptly clobber the men and f**k the women. It is what stronger groups have done ever since populations came into contact. The smaller Blacks are unable to birth large-headed half-breeds, If its is small head and a boy it does not survive childhood, if it is a girl she can do the dishes and keep the men warm at night.
It is unlikely that the Neanderthal men on their own could have evolved a society that could survive the harsh winters, I believe it needed female co-operation. Since the Neanderthal infant mortality rate was likely very much higher it does not take all that many generations for Neanderthal to totally die out.

I have lived in Africa before all that independence nonsense, I have seen how the live in the bush in Congo and East Africa and there just is no way they could compete with a tribe tht has learned to survive an ice age.

Unfortunately I have studied neither anthropology or genetics so I do not know if my ideas are totally crazy or could have some basis in fact. Would love to know which it is.

Ric said...

RIP.
As a relief, consider that what goes around comes around.

Hi Peter, I am an old reader of your blog, which I thought you left. I read about your come back from the other blog and I am happy to read you again here, but now, this post is from April. So i wonder, Is it still going on ?

In the past, I was curious about the expression 'accelerated Evolution'. I first assumed that you meant 'increased number of mutations' per length of DNA per unit of time. But I understood that it is instead the number of mutations FIXED by Natural Selection that you are considering, and according to you, this number is increasing during gene/culture coevolution.
Does this imply that the raw mutation rate is NOT a limiting factor ? and that there is always more mutations than the Natural Selection can select. If that was not the case and the mutation rate was a limiting factor, the maximal rate of Selected Mutations per generation would simply become the mutation rate.
The raw number of mutation in an entire population is also dependent of the total length of DNA considered. That is, in a big population of 1000 individuals, there in 1000 more DNA susceptible to mutations than in a population of 1 individual.
Said otherwise, In a big population, you can have many more mutations than in a small one, and therefore, even if the mutation rate per se was a limiting factor in a small population, having more individuals may overcome this limitation.

You mention an increase of around a hundred fold or more, that could be such an effect of population size. That is, if the population increases a 100 fold, then there is a 100 fold more mutations to grab for Natural Selection.
However, at the level of the individual (and for the same amount of DNA), the mutation rate is still the same. One way to increase this rate a 100 fold is a drastic manipulation of the proof reading activity of the DNA polymerase, for example. This is the way that some Bacteria respond to environmental change : during stress, they manipulate their own DNA-proof reading activity during DNA replication, which effectively increases the true mutation rate, but at the cost of many lethal mutations. They also manipulate the interspecies molecular barrier, which normally prevent the DNA of different species to recombinate with the host bacterial dna. Bacteria can be promiscuous, with foreign DNA inside them from who knows which origins. But for recombination to occur between their own DNA and this extra DNA, long stretch of identical sequence must be present, which send the signal that this extra DNA is from the same species and can therefore be used for recombination, and generate novelty. During Environmental stress however, this system is shut down, and recombination can occur between non-perfectly homologous DNA, generating even more novelty. In any case, Bacteria have several systems to increase their true 'evolution rate' and generate novelty and adaptation to environmental change. But it seems that this is always at the cost of more lethal mutations, aka many more death in the bacterial population.
I may be wrong but don't think that such systems exists for humans. Therefore it is not the true mutation rate that is changing in human and the term 'Accelerated Evolution' is confusing in my opinion. Perhaps epigenetic changes can results in creating more novelty, but a ...100 fold, I don't know.
Are you suggesting, or are you suspecting, that something like the bacterial systems (perhaps more refine), exists for humans too ?
Can you elaborate on what you mean by 'Accelerated Evolution' and are you talking about the entire population, or for single individuals ?

Peter Frost said...

Ric,

I will eventually return to blogging. At present, I am overwhelmed by work and have very little free time. There are also unresolved problems at The Unz Review.

The term 'accelerated evolution' is not my own. Unless I am mistaken, it was coined by John Hawks, who explains it on his weblog:

http://johnhawks.net/weblog/topics/evolution/selection/acceleration/accel_story_2007.html?seemore=y][b][i]John

Human evolution accelerated partly because a growing population increased the number of promising mutations. The main reason, however, was the entry of humans into a growing diversity of environments, initially natural environments and then cultural environments.

The second reason was much more important than the first. There are many cases of large populations that evolve at a very slow rate. They evolve slowly because their environment is changing slowly. So selection is a matter of finding a better fit to an existing situation. As John Hawks argues:

"... the ecological changes documented in human history and the archaeological record create an exceptional situation. Humans faced new selective pressures during the last 40,000 years, related to disease, agricultural diets, sedentism, city life, greater lifespan, and many other ecological changes. This created a need for selection.

Larger population sizes allowed the rapid response to selection -- more new adaptive mutations. Together, the two patterns of historical change have placed humans far from an equilibrium. In that case, we expect that the pace of genetic change due to positive selection should recently have been radically higher than at other times in human evolution."

Ric said...

OK, thanks for the link, so yes, it's population expansion, aka 2 humans have twice as many mutations as one human. The rest is important, but sort of irrelevant.
To me this is not the right conceptual framework to think Evolution.

Jim Bowery said...

I wonder if dogs left a detectable signature in the genome of European hunters.

There would have been greater social independence of lone hunters, aided by friendly canines. That might also have atrophied eusocial competence. What are the genes involved in that?

Ben Hardisty said...

Ric, in a growing population natural selection is more effective: in a declining population each female might have, on average, less than one offspring, whereas in a growing population each female might have, on average, more than one offspring. The probability of fixation of a new mutation is very, very low in general-- even if that mutation confers an advantage. However, as the population becomes bigger and bigger, you see in population genetic simulations that beneficial allelic mutations become more likely to make it past the point at which they are likely to become extinct more often than they do in small population.

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