Evolving Ourselves - How Unnatural Selection and Nonrandom Mutation are Changing Life on Earth


Authors: Juan Enriquez and Steve Gullans

Publisher: Penguin Group
Copyright 2015 by Juan Enriquez and Steven Gullans
Pages: 33-34

"Much of what we eat today, often in large quantities, isn't exactly what one could call all-natural. And if you really are what you eat, then we are already quite a different species. Bodies that for hundreds of thousands of years ate 'all-natural' have been challenged to adapt fast to tidal waves of nachos and pizza.

"Dental plaque provides a small window through which to view this massive evolutionary upheaval. Anyone who has been to the dentist knows how tough it is to remove plaque. Bad for you, but good for science. Its toughness makes plaque a great reservoir of data for bioanthropologists. Diet affects plaque, and by comparing the plaque in ancient and modern human teeth, scientists can infer what kinds of things we ate and what lived in our mouths.

In the pre-Twinkie era, both early humans and our close relatives had mouths that were quite healthy. There are almost no examples of Neanderthal cavities. Paleolithic and Mesolithic human skulls are almost devoid of cavities.

"As human diets began to modernize, as we began cooking and cleaning more of our daily foodstuffs, a strange thing happened: The bacterial colonies in our mouths became far less diverse. Hunter-gatherers from seven thousand years ago had far more microbial diversity in their mouths than did Stone Age agriculturalists. Bacteria that had coexisted and coevolved with our bodies and diets, that had adapted, were crowded out by a new environment, and our mouths became colonized by nastier bacteria. We further repopulated our mouths with the ever more widespread use of processed sugars. The incidence of cavities exploded. We began to suffer chronic oral disease, something that became most bothersome, and sometimes even deadly, in the pre-antibiotic, pre-brushing, pre-dentist era.

The teeth discovered in a cave outside Tel Aviv in Israel were found to contain tartar more than 400,000 years old. (Photo: Israel Hershkovitz/Tel Aviv University)

"These days we need to do things no self-respecting Neanderthal would have considered: brush our teeth three times a day, floss, drink fluoridated water, fill cavities, and use dentures. (It's worth noting that these practices are far from common, or necessary, in any wild animals.)

"Our changing diet wasn't just hard on our mouths. Average male height during the ninth to eleventh centuries was just below that of modern men. But the transition into the Middle Ages, the Enlightenment, and the Industrial Revolution was brutal. Disease, wars, serfdom, and filthy cities changed the morphology of men; by the 1700s, the average Northern European was 2.5 inches shorter than before and did not recover until the twentieth century.

"Evolving diets redesign our bodies in other ways. The average U.S. male increased his weight from 166 pounds in 1962 to 191 pounds by 2002. By 2011 we had gained, on average, a further five pounds. If we had observed this kind of generalized transformation in the bodies of a wild species, we would be shocked. But Darwin and his theories could have predicted much of this change; indeed, he saw hints of it in his studies of animal husbandry and how a species rapidly changed and adapted under human-directed breeding. So he would not have been terribly surprised observing the changed morphology of a gaggle of modern humans as they perambulate by with their monster soft drinks in hand."