The authors claim, for instance, that the Indo-European expansion was principally enabled by lactase persistence in the founding population of proto-Indo-European speakers, who then migrated across the Eurasian continent fuelled by their ability to digest cows' milk. They also claim that Ashkenazi Jewish successes in business, media, the arts, and science - all of which are demonstrable, I should think - have been enabled by their genetically inherited superior intelligence, a direct result of competition for jobs and status in Ashkenazi communities in Europe over the last millennium or so. The competition for such things, and the fatal consequences of failure, selected for intelligence. Voila - Ashkenazim are on average more intelligent than other Europeans. (Other attempts, notably the fantastic The Chosen Few by Botticini and Eckstein, have tried to show that such achievements have more to do with culture and literacy than genetics, but these are by far the strongest arguments Cochran and Harpending make in their book.)
'HBD-ers' extrapolate from this that almost all of human culture is genetically inherited, which is an unwarranted extrapolation. It is trivially untrue, for a start. While languages can correlate with some genes now and then, the genes do not cause you to speak your language - your experiences, combined with thousands upon thousands of years of history, do. The clothes you wear are not determined by your genes; fashion has changed considerably in a couple of generations, far too short a time for genes to be behind the differences in attire between 1914 and 2014. The food you eat isn't determined by genes (aside from e.g. lactose intolerance), but again by cultural history - world cuisine changed dramatically in the wake of the Columbian Exchange, for example. Your hobbies are not determined by genes - there is no gene for watching television, and pretty much anyone, it seems, can learn how to read or play basketball recreationally, even if some people are better at these things than others. In a very important sense, culture is determined by history, and rarely by genes.
That isn't to deny that humans have a great deal of shared phylogenetic inheritance that is behind certain general human proclivities ('human nature'). It is merely to say that human cultural variation is not determined by human genetic variation, which is definitely the case. It would be foolish to deny it.
***Cochran has also claimed in a recent blogpost that indigenous American history may primarily be explained by the comparative lack of genetic diversity in the Americas. Afro-Eurasia is dominated by a few language families - Sino-Tibetan, Indo-European, Afroasiatic, Niger-Congo, Austronesian, and so on - while there were hundreds of families in the pre-Columbian Americas. Cochran has claimed that because of the lower level of genetic diversity in the Americas, a result of the relatively recent human migration from Eurasia, no single human group would acquire a lasting advantage over all the others. They were unlikely to acquire genes for lactose tolerance or anything like that, and therefore wouldn't be able to spread themselves around like speakers of Indo-European languages using lactase persistence (never mind that IE languages probably spread due to socio-cultural innovations).
The Americas were not static in prehistory, and there were plenty of dominant language families, including Tupian, Arawak, Uto-Aztecan, Quechuan, Chibchan, Algonquian, Athabaskan, Iroquoian, and Souian. These were spread over very large areas and were spoken by lots of people. They seem to have spread through socio-cultural advantages, like agriculture or the bow and arrow, and if the Americas were significantly less dynamic than Afro-Eurasia, then that may be chalked up to the north-south orientation of the continents, the necessity to adapt maize for more northerly climes, and the absence of the horse and camel.
***HBD-ers appear to have an extraordinary interest in IQ, as well, and see this as a driving force behind cultural 'achievements'. That's something I can't fathom: there doesn't seem to be any reason to correlate high average IQ with the ability to build monumental architecture or generate a large agricultural surplus or domesticate crops, and these seem to be the things that drive literacy, exploration, conquest, and everything else.
The focus on IQ seems unhealthy. I probably shouldn't have to point out, either, that such a focus is often behind crazy claims ranking the 'races' - 'Asians' above 'whites' above 'blacks' (never mind that these 'races' don't really exist and that human biological diversity is clearly much more complicated than this).
HBD-ers claim that differences in IQ are related to the complexity of the societies in which the people have lived for the past few thousand years. Competition for jobs and resources in more complex, literate, urbanised societies will ensure a high degree of selection for intelligence, increasing IQ over time. Smaller, simpler, non-literate, non-urban societies will not select for intelligence, and therefore, apparently, we can expect all of sub-Saharan Africa to have a lower IQ than western Europe or east Asia.
That might even make sense as an explanation (assuming that there even is such a pattern in the data) were it not for the fact that large parts of sub-Saharan Africa were very complex in the pre-colonial era, including most of the Sahel, the savanna/rainforest border in west Africa, almost the entire east African coast, Ethiopia, Nubia (i.e., northern Sudan), the Zimbabwean plateau, the rainforest near the mouth of the Congo, the Great Lakes, and plenty of other parts of inland Africa (the archaeological evidence indicates considerable social complexity all over the place, actually, and any good book on pre-colonial Africa ought to show this). I would also note that due to sub-Saharan Africa's low population density, these settled complex societies constituted the bulk of sub-Saharan Africa's people.
Competition for trade and jobs would have been greater, earlier, and for longer on the Swahili coast than it was in Anglo-Saxon and medieval England, so why should we expect higher average IQ in England than in Tanzania? Or, better yet, why should we expect Irish people to perform anything like as well as Nigerians, given that Ireland was poor, exploited, and rural for hundreds of (apparently crucial) years while much of west Africa was urbanised and densely populated for the same time frame? How could the descendants of poor Irish folk, like JFK and Conan O'Brien (and me!) be able to achieve anything at all, given the rural and unsophisticated nature of their homeland?
If there is a noticeable difference in performance on IQ tests, perhaps we should be looking at other factors, like colonial history, corruption, tax, trade, teaching standards, parental literacy, and so on. The idea of looking at these factors was recently mocked by Greg Cochran in a blogpost that boggles the mind for the sheer amount of sociological and historical illiteracy it demonstrates, but it seems common sense to look for socio-cultural explanations for differences in economic output and academic achievement instead of reaching straight for genetic differences.
***Natural selection is powerful, and there's no real reason to believe that selection hasn't operated on human populations since they started to separate from one another a couple of hundred thousand years ago. But some HBD-ers - not all, I don't think - want to explain cultural changes that took place over the course of only a few generations in terms of natural selection, and I don't think this makes any sense whatsoever. An attempt has been made to write European history in terms of genetic changes, and it is beyond laughable (it also barely bothers with actually showing how such-and-such a system imposed actual selective pressures on the people involved, so in terms of causal mechanisms, it's rather lacking, to put it mildly). Natural selection may be powerful, but human brains and character are extremely complex things, and without extreme pressures it seems unlikely that socio-cultural changes over the course of five or six generations will be capable of causing any significant changes in personality, temperament, or even IQ.
That account also makes bizarre claims, like the idea that altruism is greater in societies that have complex marriage systems and that 'marry out' of the family unit - because, apparently, when you marry out of your circle for generation after generation, everyone you meet is almost guaranteed to be your relative and therefore worthier of compassion!
Does this square with anyone's experience of living in a society like that? I certainly don't see the people around me as probable relatives, and I live and have always lived in such a society. It is pretty clear from a variety of studies (primatological, ethnographic, and so on - see in particular Bernard Chapais's classic Primeval Kinship) that the basis of human kinship is imprinting in childhood, not whether you know that others around you are, in some sense, your kin.
You will instinctively feel that a girl you grew up in the same house with is your sister, but you will feel considerably weaker emotions about someone you know to be your biological relative but whom you only met in adulthood. Imprinting is the mechanism, and that isn't commensurate with the claim that everyone being related in some sense generates greater altruism because, simply, you can't grow up with all of those people. There's no naturalistic way for it to affect your psyche.
Humans can change culturally without genetic change. They do it all the time. They learn to speak new languages, eat new foods, use new devices, read new books, use new weapons, farm new crops, trade with newly-found populations, and adopt new beliefs about the universe. Genetic variation cannot explain human history. Even in those pesky cases in which genes do cause significant variation, as with lactose tolerance, humans inevitably find ways around them. The Indo-European expansion may have been caused in some small, insignificant part by lactase persistence enabled and necessitated by their pastoral economy, but Mongolian pastoralists with similar economies are lactose intolerant and ferment their dairy products to circumvent the need to adapt genetically. Variation in genetics is much less important than environment, ecology, and historical circumstance in determining cultural practices.
***Here's a big problem for HBD-ers to resolve. For thousands of years, western European societies were full of superstition, religion, religious bigotry, and religious (and other) violence. To be a heretic, or to agree with heresies or heretics, was sufficient cause for arrest and brutal murder, meaning that religious belief and religious orthodoxy were actively selected for. To disagree with the imposition of the death sentence for a heretic, to seem unorthodox, to not rejoice at the discovery and burning of witches - all of these could lead to execution. This went on for hundreds of years, was extremely widespread, and was strongly selected for. This is the kind of selection that, if such things were possible, would certainly lead to higher levels of superstition or religious hatred encoded at some genetic level.
Western Europe nowadays, of course, is one of the least religious, least violent, and least superstitious places on the planet. Murder rates in most of western Europe hover around 1 in 100,000 and a tiny proportion of the European population is killed deliberately by another person. The death penalty is entirely absent from Europe (aside from Belarus) and torture and witch burnings are no longer practiced.
This all changed incredibly quickly, within a couple of hundred years, and it happened in clear and obvious defiance of strong selective pressures to conform to the prior pattern of violence. Natural selection in favour of such things meant nothing in the face of expanding trade, strong states, reason, improving hygiene, and the expansion of knowledge about the universe.
This is because the main thing to bear in mind about people is that they're all generally quite capable of living on the earth and learning new things. They can take in and improve new ideas, given sufficient means and stimuli. Genetic variation is absolutely fuck all compared to that.