By Carrie Arnold
Despite its name, the Paleo Diet is a new food trend, one which has become increasingly popular in recent years. The diet’s basic tenet is that our bodies haven’t yet evolved to cope with the changes to our food intake as a result of agriculture. Paleo Diet aficionados hold that grains like wheat are making us fat and unhealthy, and that we would be far better off if we ate how our ancient ancestors did, focusing on lean meats, fruits and vegetables.
What researchers haven’t been able to answer, however, is exactly what our ancestors ate. Early humans and our other hominin predecessors lived pretty much everywhere, in environments as diverse as the Arctic, tropical rainforests and deserts, and so its likely that diet varied by region. Even within a given region, reconstructions of diet have had to rely on tooth analysis or bones found nearby.
A quartet of papers published today in Proceedings of the National Academy of Sciences have instead turned to stable isotope analysis, which analyzes the specific chemical signature of molecules, to determine the diets of a variety of ancient hominin species by looking at their fossilized teeth. The findings show that human ancestors started moving away from the traditional ape diet of fruit and leaves about 2.5 million years ago—much earlier than previously thought. Thus, even our “paleo” ancestors may never have eaten a paleo diet.
Razib Khan’s degrees are in biochemistry and biology. He has blogged about genetics since 2002 (see his Discover Blog, Gene Expression), previously worked in software development, is an Unz Foundation Junior Fellow and lives in the western US. He loves habaneros.
…At some future period, not very distant as measured by centuries, the civilized races of man will almost certainly exterminate and replace throughout the world the savage races. At the same time the anthropomorphous apes, as Prof. Schaaffhause has remarked, will no doubt be exterminated. The break will then be rendered wider, for it will intervene between man in a more civilized state, as we may hope, than the Caucasian and some ape as low as a baboon, instead of as at present between the negro or Australian and the gorilla.
The above quote is not to vilify Charles Darwin. On the contrary, I believe Darwin was a scientific hero whose work is the foundation of modern biology. Nevertheless, he was a man of his age. Despite the fact that Darwin was a political liberal from a family of liberals, with pristine credentials in progressive social movements of his day, such as the anti-slavery campaigns, it is clear that he had Victorian biases nonetheless; some of the passages in The descent of man clearly come from a fortunately bygone era, when white scholars and adventurers cataloged and surveyed the unexplored corners of our world, and created taxonomies of the “lower races” as if they were just part of the local fauna. The reality is that Charles Darwin’s age was fundamentally one of white supremacy. In the year 1900, one out of three human beings alive was of European extraction. In the four centuries since Christopher Columbus, Europe and its Diaspora had entered into massive demographic expansion—which many Victorians saw as survival of the fittest. Progressives of the late 19th and early 20th century, such as H. G. Wells, foresaw a future where the “higher races” would naturally marginalize those peoples who were lesser participants in civilization. Such was taken as the judgment of nature.
How 100 years do change things. And yet just as Darwin could not help but reflect the presuppositions of his era, so we in our day can not help but channel the zeitgeist. Like Charles Darwin, today’s scholars have concluded that humans are fundamentally an African species. But unlike Darwin they conclude from this that there is a biological, essential unity of humankind, such that talk of “civilized” and “savage” is rendered moot and irrelevant. We do look through the mirror of our ages darkly, seeing startlingly different insights from the same shadows of reality. Whereas racist assumptions and beliefs were supported by interpretations of science of the 19th century, today we attempt to harness science in the opposing direction.
The topic of human variation, and more plainly, race, is fraught. The past century has seen a wild swing from the widespread acceptance of the idea that human races are real, with big, important differences, to the opposite position: that race is fundamentally an illusion, a social construction of the human mind. But both of these arguments are mistaken. The established modern consensus about the equality of people, irrespective of race, is morally and ethically justified. But these beliefs we hold to be true do not derive from the natural science, which doesn’t present a clear moral lesson.
Every few years it seems that the British biologist Steve Jones declares the death of evolution by natural selection in the human species. The logic here is simple even to a schoolboy: evolution requires variation in fitness, and with declining risk by death during our reproductive years humans have abolished the power of selection. But this confuses the symptom for the disease. Death is simply one way that natural selection can occur. Michelle Duggar has 19 children. The average American woman has around two by the end of her reproductive years. It doesn’t take a math whiz to figure out that Michelle Duggar is more “fit” in the evolutionary sense than the average bear. Even without high rates of death, some people have more children than other people, and if those people who have more children than those who do not are different from each other in inherited traits, evolution must occur. Q.E.D.
But you probably shouldn’t be convinced by logic alone. Science requires theory, experiment, and observation. (If you’re talking humans, you can remove the second from the list of possibilities: there are certain unavoidable ethical obstacles to experimenting on human evolution—plus we take far too long to reproduce.) But humans sometimes have something which bacteria can not boast: pedigrees! Not all humans, of course. Like most of the world’s population I don’t have much of a pedigree beyond my great-grandparents’ generation. But luckily for biologists, the Catholic Church has long taken a great interest in life events such as baptism, marriage, and death, and recorded this info parish by parish. With these basic variables, demographers can infer the the rough life histories of many local populations over the centuries. In many European nations, these databases can go more than 10 generations back. And some aspects of human evolution are revealed by these records.
What aspects am I talking about? Reproduction itself. Not only is variation in fitness one of the primary ways by which evolution occurs, but it is also a trait upon which evolution operates! How else are there rabbits which breed like…rabbits, and pandas…which don’t. There is often variation within species for the odds of multiple births, age at first reproduction, and lifespan, depending upon the differences in selection pressures over a population. And that seems to be exactly what occurs in human beings. There is interesting evidence for evolution of reproductive patterns from populations as diverse African pygmies and Finns, but more recently some researchers have been plumbing the depths of the records of the Roman Catholic Church in Quebec, and they’ve come back with gold.