Friday, December 14, 2012

Natural Selection, Diet and Health

I've been on a reading jag about evolution: The Greatest Show on Earth  by Richard Dawkins and Why Evolution is True  by Jerry A. Coyne. I also threw in Dawkins' 1991 Christmas Lectures titled "Growing up in the Universe."  (Link goes to online videos.) A few things worth knowing (among many others):

Evolution hasn't made our bodies perfect. The earliest life was bacteria, and all life forms have changed by tiny increments ever since. There was no going back to the drawing board and starting a new, more logical design. For instance, our maxillary sinuses draining at the top is a trait we inherited from ancestors who walked on all fours (their sinuses drain at the front).(1) Both books have an entire chapter on parts that have evolved badly. Good fuel helps a lot, but it won't fix a bad design.

Natural selection can occur rapidly. We're all familiar with bacteria evolving resistance to antibiotics. But natural (or artificial) selection has been observed over periods of years or decades in changes in elephants, birds, insects and other animals. Perhaps for the Kitavans, Japanese or Inuit (isolated populations), some natural selection has occurred also. Take someone who has health problems on a starchy diet. How many descendents would he or she leave on a Pacific island where the fare was mostly fruit and root vegetables? Much is made of the healthy, rice-eating Japanese, but it's rarely mentioned that Japan went through a 1,200-year period of enforced pescatarianism.(2)

It's well known that dogs descended from wolves--but how? There's an idea that wolves scavenged humans' garbage dumps and those that were less afraid of humans self-selected into gradual domestication. (Dimitri Belyaev, a Russian scientist, domesticated foxes to the point that they acted like dogs using the same principles.) (3) The point here is that humans wasted meat--enough meat to attract and feed packs of wolves and dogs. Just because lean game animals have a certain percentage of fat doesn't mean that was the percentage of fat in the human diet.

Gills evolved into thyroid and parathyroid glands.(4) Someone else will have to figure out the implications.

1. The Greatest Show on Earth by Richard Dawkins, p. 370. Simon & Schuster, 2009.
2. VB4-Japan. The Cambridge World History of Food. Accessed December 14, 2012
3. Dawkins, p. 73-74.
4. Dawkins, p. 360.

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