The increase in height has to do with hygiene, nutrition and medicine, not evolution.
We Will Not Be Giants
Frans de Waal is the C. H. Candler professor of Primate Behavior and director of the Living Links Center at the Yerkes National Primate Research Center at Emory University. He is also a member of the National Academy of Sciences and the Royal Dutch Academy of Sciences. His latest book is “The Age of Empathy.”
Updated May 16, 2011, 1:24 PM
The evolutionary account of why the Dutch, with an average length of 6 foot 1 for men, have become the tallest people in the world is that length offers a great advantage in a super flat country: tall people see farther than anyone else.
This is nonsense, of course. There is no evidence whatsoever that the growth in human height over the last few centuries has anything to do with evolution by natural selection. Evolution works by favoring certain genomes over others. The increase in human length is too fast to be explained by genetic change. Rather, it must have to do with progress in nutrition, hygiene and medicine. As such, it also tells a story about health care systems and prenatal care, which may explain why Europeans have grown even more in average length than Americans, and are now on average one or two inches taller.
These effects are by no means unique to humans, though. It is well known that most zoo animals grow larger, reach maturity earlier and live longer lives than the same species in the wild. The average lifespan of chimpanzees is at least 10 years longer in captivity. There are also substantial size differences, with adult male chimpanzees weighing around 50 to 60 kilograms at zoos, but only around 40 kilograms in the wild. No one views this as evolutionary change; it is all environmental.
It is interesting to note that the lengthening of the Dutch has come to a halt. It stopped around 2001. Some scientists have speculated that humanity may have reached its genetic limit, for now. So, perhaps we shouldn't worry too much about an endless increase in height.