International Balzan Foundation Luigi Luca Cavalli

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1999 Balzan Prize for Science of Human Origins There has been a tendency in some sociobiological circles and their descendants to consider cultural traits as dominated by biology, but the reverse is becoming the rule. There is unquestionably a range of new genetic traits which have been introduced as an answer to cultural changes. Most of them have to do with acquired cultural traits introduced by new diets or customs, like getting dressed. The expansion toward northern Asia would have been impossible without clothing. Whether clothing was determined by the previous loss of hairiness, or whether it helped loss of hair is difficult to say, but it is likely that hair loss took place earliert and made clothing necessary. One may also venture that hair was lost because fire had become a major presence in human life, and hairiness is dangerous in proximity to fire. Another genetic change having specific racial consequences is paleness of the skin. That skin became pale was largely a consequence of a cereal-based diet, which, in dark-skinned people, causes rickets at northern latitudes. Wheat does not contain vitamin D, but a chemical substance that is its precursor, which can be converted into vitamin D only by an enzyme present in the lower layers of the skin. This enzyme, however, must be activated by ultraviolet rays, which are too scarce in Europe because of its high latitude. The melanin responsible for the dark color of the skin stops ultraviolet rays, whereas pale skin allows the formation of vitamin D in a diet based on cereals and cancels out the highly harmful consequences of rickets. Another example of the biological consequences of cultural evolution is intolerance to milk (and tolerance to it). Practically all mammals lose the ability to use lactose after being weaned, but among many herding peoples, the custom of drinking milk among adults became widespread, even though this may give rise to serious cases of lactose intolerance. A mutation that arose among herders in the Ural Mountains around 6000 years ago abolished the disappearance after weaning of the enzyme that makes it possible to use lactose, and the carriers of this mutation are totally lactose tolerant. Today this mutation is found in 90- 95% of Scandinavians, is very frequent in northern Europe, a little less in central Europe and present in 20-40% of southern Italy. The heredity of acquired behavioral characteristics through cultural evolution is a reality that enables characteristics transmitted via cultural routes to overcome the great slowness with which normally favorable biological characteristics spread through populations: thanks to biological heredity alone. The spread of lactose tolerance is an example of one of the most rapid biological evolutions in humans, though it was undoubtedly helped enormously by the spread of milk 16
Luigi Luca Cavalli-Sforza consumption, especially among adults, which came about through a Lamarckian type of heredity (of acquired characteristics during lifetime). The genetic study of human evolution has shown with extreme clarity that the genetic success of a population, as proved by its expansion in numbers and across vast regions, was largely the result of major technological innovations in relatively recent times: food production (agriculture, stockbreeding and their various developments) or transportation (cattle, horses, camels, lamas, boats, oceanic navigation), or military power (bronze, iron, cattle and horses, camels) and, in more recent times, communication (roads, and again the horse, the telephone, radio, television, and so on), mathematics (agronomy, geography, astronomy, computers), the experimental method (engineering, chemistry, modern physics). With the modern triumph of communication cultural evolution is becoming more and more the directional force of human evolution, and genetic evolution may well end up be completely under its control. Even the evolution of animals and plants is undergoing intense acceleration as a result of cultural evolution in humans. The remote origins of the success of humans as a species lie in two innovations which are partly biological, but perhaps in part also cultural. The first is language, which certainly required a strong development of the essential parts of our brain, and which was hence largely a biological evolution. However, once it became possible to use it, it developed enormous driving force. The other was human ingeniousness, which brought about many cultural innovations, the usefulness – if not necessity – of which has been proved beyond a doubt. Unlike genetic innovations due to mutation, which are by chance, cultural innovations are responses to a necessity. However, they are not always wholly appropriate, and like all innovations, they may also have costs that are heavier than their benefits. Racism I do not like the word “race” because it corresponds to old subdivisions that are inconsistent with genetic reality and unjustifiable by a rational classification. Moreover, there is no real use for such classifications and, what is worse, there is always an associated racist flavor. Darwin had already recognized the difficulty of a rational classification of races in what is an almost perfect continuum, and noted the enormous variety of numbers and definitions of races, from two to almost one hundred. The current trend toward increased admixture can only make the idea of race even less clear. 17
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International Balzan Foundation Luigi Luca Cavalli

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