The 10,000 Year Explosion - a book review

In The 10,000 Year Explosion: How Civilization Accelerated Human Evolution Gregory Cochran and Henry Harpending argue just that: human evolution is advancing faster and faster. Cochran and Harpending are anthropology professors at the University of Utah.

 They present three reasons why human evolution is moving faster. First, during the last 10,000 years the human population has grown from an estimated five million to over six billion.

 Other things being equal, a large gene pool will evolve faster than a small gene pool. This is because there is more scope for beneficial mutations.

 Second, during the past 10,000 years humans have experienced a very different environment from the one that shaped previous human evolution. This is because of the development of farming and urban living. Farming originated in the Near East 10,000 years ago; civilization began there 5,000 years ago. The life of a stone age hunter is exciting, varied, and dangerous. In order to survive a farmer needs to be self disciplined, and he needs to be able to plan for the future. No matter how hungry he gets, he cannot eat his seed corn, or butcher all of his farm animals. Spending all day, day after day plowing fields or harvesting crops is tedious and exhausting, but it has to be done.   
 During the six million or so years of uniquely human evolution intelligence was important, or human intelligence would not have reached the level it did 10,000 years ago. Nevertheless, urban living places an even higher premium on superior intelligence. Those who are intelligent enough to become merchants, artists, and government officials live better lives than laborers, and have more children who survive and reproduce.  
 Moreover, over a period of centuries the criminal justice system of a civilized nation removes those with criminal inclinations from the gene pool. As farmers breed tamer domestic animals, governments breed tamer citizens.  

 Third, travel has become longer and faster. Even before the invention of steam ships, trains, cars, and planes, horse and camel transportation made it possible for men to travel long distances and spread their genes. Those genes which gave competitive advantages continued to be transmitted. Those which gave competitive disadvantages died out, along with those who inherited them.

 All of this should make sense. Nevertheless, the consensus has been what Stephen Jay Gould stated when he wrote, “There’s been no biological change in humans in 40,000 or 50,000 years. Everything we call culture and civilization we’ve build with the same body and brain.” 

 Why would so many people believe something so counter intuitive? 

 Political correctness. If one wants to believe that race is a social construct, that “we’re all the same under the skin,” that IQ differences don’t matter, and that there are no significant racial differences in average aptitude and behavior, one needs to believe that little or nothing has changed since the races differentiated 40,000 years ago. If one acknowledges persistent differences in performance and behavior between the races, one has to disagree.

 One obvious and not very controversial area in which people have changed during the past 10,000 years is in the spread of lactose tolerance. Most mammals lose the ability to digest milk sugar after they are weaned.  At several different times and in several different places individuals had mutations that allowed them to digest lactose all of their lives. By making it possible for adults to drink milk, this gave them an advantage against starvation, so their descendants were much more likely to survive and reproduce. Currently most people who speak an Indo European language, Arabs, Mongolians, and several African tribes who have tended cattle for over a thousand years can drink milk all of their lives. Most humans cannot.

 Another rather controversial area where humans have evolved is in the superior intelligence of most Ashkenazic  Jews. These have average IQs estimated as 112 to 115. Cochran and Harpending argue, and this is becoming the (quiet) scientific consensus, that they evolved that intelligence because after Europe converted to Christianity they were restricted to professions, like commerce and money lending, that required superior intelligence. Those who could not learn the necessary skills did not survive and reproduce. Cochran and Harpending point out that Jews whose ancestors lived for centuries in places other than Europe do not have higher average IQs, and that during the ancient world Jews were not considered to be especially clever, although Greeks were. 

 The 10,000 Explosion explains why the longer a population has practiced farming and urban living, the higher its average intelligence is, and the lower its crime rate.

 Nevertheless, the correlation is not exact. With a nearly all white population, Russia has a much higher murder rate than multi racial United States. Although farming and civilization began in the Far East about two thousand years after they began in the Near East, Orientals have lower crime rates and higher average IQs than Caucasians.

(emphasis added)

Why would I buy their book when I can read my fill of ignorant yammerings about evolution free of charge?

There’re so many factual inaccuracies in that post and it’s so scattershot that I don’t even know what your point is.

Yeah, that’s another advantage to reading the Answers in Genesis web site instead – their misunderstandings of evolutionary theory are actually more logical and coherent.

How is this counter-intuitive? It seems like the likeliest explanation to me.

As you point out, evolution used to take millions of years to have a noticeable effect. Why should a biological process suddenly accelerate a hundredfold? And only for one species?

The likeliest explanation is that it didn’t accelerate. Evolution is still working at the same pace it always did and the rapid changes in how humans lived over the last few thousand years are caused by some non-evolutionary effect.

Geez – I intended those comparisons between the authors and the Answers in Genesis people as jokes… but I just realized that the authors’ viewpoint is a lot more understandable if one assumes them to be Creationists. Sudden rapid changes favoring particular chosen peoples makes perfect sense from a no-nonsense, no-metaphors, six-twenty-four-hour-days creationist viewpoint: God cursed the descendants of the son who watched Noah getting drunk off his ass and blessed the son who was more properly filial; that explains everything!

And 10.000 years is also a suspect number, in that light.

To be fair, we ought to consider the points offered and see what predictions follow therefrom and how the correlate to reality. For example:

Given that the criminal justice system cracks down hard on poor people and minorities while letting the ruling-class rich skate, this explains how society has literally bred a generation of Kenneth Lays and Bernie Madoffs. So, we can’t be completely dismissive of this particular thread of argument, at least.

So the smartest, most peaceful people in the world are in…Iraq?

ETA: or from the other end, people in Korea and Japan came to agriculture relative late compared to the rest of Eurasia (in the case of Japan, very late). I don’t see much evidence that Koreans or Japanese are particularly stupid or crime-prone.

I hesitate to say anything which will be interpreted as supporting NDD, but in fairness there are many factors that can influence the species-wide “pace” of evolution. Species population is a basic one; more individuals and more reproductive acts at a time means more opportunities for genetic drift, other factors being equal (which they aren’t, but still).

Also, evolution isn’t only a biological process, in that non-biological cultural factors can influence biological evolution.

This is not to say that Stephen Jay Gould wasn’t largely right about the last 50,000 years. Our most important “evolution” since then has been non-biological cultural evolution–including in my view a radical learned revamping of the way we use our brains–but the essential biology of those brains probably hasn’t changed much. (Though there’s room to debate what’s essential; I count the folding back of the Neanderthal branch into the larger human population as a minor wiggle.)

New Deal Democrat made this inaccurate assertion in another thread, but it does not become more true by repetition.

Large populations tend to dilute mutations, whether beneficial or otherwise. Small populations, indeed tiny, isolated populations are most likely to see relatively rapid fixation of genetic change.

This is just one of the many factual inaccuracies that make the entire argument a failure.

But as CannyDan already pointed out, the larger number of random mutations that occur in a larger gene pool is balanced by the fact that mutations have a smaller effect because the overall gene pool is larger.

Beneficial mutations do not get diluted; they spread. If a person with the ability to drink milk all of his or her life has children by a person without this ability, the children do not retain the ability to drink milk until they are adults, they inherit the ability or they do not. Those who inherit the ability are less likely to suffer malnutrition or starvation, so they are more likely to survive and reproduce. That is how, from a small number of mutations that happened several thousands of years ago in a few individuals, a large minority of the human population can drink milk all of their lives.

But a large species population distributed over a large area represents more opportunities for sub-populations to be temporarily isolated.

I don’t want to get mired in accusations, but I’ve actually read the book and found it interesting. Some of the arguments are extended too far to convince me, but much of the book is a good summary of modern thought.

The Gould issue is simply a strawman, though. Ever since DNA evidence became common, the notion that evolution has been speeded up by the continual increase in mixing of different populations has been the new consensus. It’s not remotely controversial anymore. It is also not the same thing as what CannyDan refers to, which is the increased expression of recessive genes found in inbred populations. Different issue. Oddly, hunter-gatherers probably had fewer problems with this because they traveled over large areas and met other populations, all of whom had incest taboos that prevented too close inbreeding. It’s after humans populated the earth that some got stuck in isolation, while the majority interbred like no other species ever had a chance to.

However, you have to understand that evolution in this sense refers to tiny, localized genetic differences. The OP correctly refers to the spread of lactose tolerance, which is the archetypal example. That’s a simple mutation to one gene, so that the body never sends out the signal to stop producing the lactase enzyme after weaning. Presumably a small number of humans always had this mutation, but it gave no reproductive advantage until herding and milking became common. When it did, it spread worldwide, though it’s still in a minority of living humans. Some evidence shows 43 variations, indicating that it happened time and time again, rather than one time that spread everywhere.

This is evolution at work in historic time. It’s not X-men type mutations and not a new species and not even visible to the naked eye. But hundreds of similar mutations are now known, and more are found in seemingly every issue of every journal.

I am not qualified to judge the specific claims of the book. It does read like serious popular science - and there is obviously such a thing - and provides extensive back-up and cites. Of course, other controversial books also do that, but it didn’t read to me like a Bell Curve sham of bias and racism. Ever since genetic evidence has become so comparatively easy to obtain, the scientific consensus has swung back toward nature over nurture and this book is an example. That doesn’t mean that culture is not operative, or that it doesn’t have an effect, or that it doesn’t have a huge effect. Humans are a nature/nurture mix, with every single trait being a greater or lesser percentage. The authors often swing too much into nature for my taste but I don’t have to agree with every single thing they say. It’s the people who make absolute statements who need to defend themselves.

Untrue. There is no guarantee that a beneficial mutation will be spread, or otherwise become “fixed” into the genome. Not even a trait that would be obviously advantageous, let alone something rather well hidden by common factors of biology (adults normally do not nurse) and cultural practice (again, adults normally do not nurse).

Take your example, assuming your own statement that most adults are unable to consume milk. My brother-in-law, for instance, would suffer considerable distress if he accidentally or deliberately drank a milk product. This is different from merely not benefitting nutritionally, understand. So given a population of adults who actively avoid drinking milk because of its effect, we now postulate a mutation allowing one to do so. (Actually, this is probably an instance of neoteny, and not a novel mutation, but the exact mechanism is unimportant for this discussion.) The mutation appears in a single individual. On what basis is it likely to spread? Just because it’s “good”?

And who is going to find out that they have this “beneficial new” gene? Will they just give milk a try one day, knowing that everybody around them suffers distress upon ingestion? And having made the experiment, will they offer milk to prospective mates as part of the courtship process? And then of course reject the ones that puke, even if they’re drop dead gorgeous or otherwise wonderfully compatible?

This demonstrates a complete lack of understanding of the processes of evolution. Indeed, whether NDD intends it or not, as suggested upthread, this argument does seem to comport favorably with creationist misunderstandings. The opening statement in the quote above reads as an article of faith, not as an evolutionary theorem.

On preview, thanks to **Exapno Mapcase **for a mechanism. But this still demonstrates that even a beneficial mutation, which might have occurred many times in the history of mankind, did not guarantee that it would be spread until particular circumstances combined. And even here, there was no guarantee.

I am actually reading this book now, about halfway done.

No there are no guarantees, but a beneficial mutation has a chance to spread which is based on the advantage it gives. If a gene conferring a small advantage is only encountered once it will probably be lost. In the example the book gives a gene conferring a 5% advantage has a 10% chance to spread. If it is encountered multiple times the chances combine, it does not take too many encounters for the chance to rise to 50%, or 90%.

There is more scope for all mutations. Remember, “evolve faster” just means “change faster.” Evolution is non-teological. It does not go from “lower” to “higher” life forms – the terms are scientifically meaningless – though sometimes it does go from “less complex” to “more complex”; but always it goes from “well adapted to survive in its environment” to “as well or better adapted”. In some cases, becoming “better adapted” means what humans might adjudge to be going down what many of us think of as the “evolutionary ladder”.

Good basic source here: The TVTropes pages on Evolution and Evolutionary Levels. From the latter:

Who said anything about a guarantee? It is more probable.

At this point, are you still summarizing Cochran and Harpending, or adding your own comment/analysis?