“If there has been no spiritual change of kind / Within our species since Cro‑Magnon Man …” Louis MacNeice, who wrote this nearly 80 years ago, could be excused a little poetic licence, but it is only 12 years since the distinguished evolutionary biologist Stephen Jay Gould expressed more or less the same idea: “There's been no biological change in humans in 40,000 or 50,000 years. Everything we call culture and civilisation we've built with the same body and brain.” Not only has this become received scientific wisdom but it has passed into popular consciousness and spawned fad diets. Marlene Zuk is an evolutionary biologist at the University of Minnesota and Paleofantasy targets the movement that insists we are biologically adapted to a Palaeolithic diet and lifestyle. On the face of it, the idea seems plausible: in the standard model of human evolution, anatomically modern Homo sapiens have been around for around 200,000 years, only 10,000 of them as farmers, let alone modern industrial people. Evolution is slow, so it stands to reason that we haven't had time to adapt to the huge changes in our lifestyle. Many evolutionary biologists, however, including the author of this book, believe that this is wrong. The changes wrought in the human genome by settled farming and the consequent enormous growth in population can indeed be seen: they are profound and have been rapid.
“Drinka Pinta Milka Day” could be the slogan for the new thinking. It would have made no sense to the Cro‑Magnons (from around 43,000 BP) because, even if they could have collected milk from the wild animals they slaughtered for meat they would not have been able to digest it. All mammalian babies can digest milk, but the gene that allows this switches off at the age of weaning. Except in many modern humans. In the most northern human populations, ie Scandinavian, almost 100% can digest milk. The percentage declines as you track south‑east. A single base pair mutation allows adults to drink milk. It emerged around 7,500 years ago with the first dairying in southern Turkey, and as these herders moved north and west the milk drinkers out-bred the rest. This is rapid evolution and it's not the only case.