The 10,000 Year Explosion
How Civilization Accelerated Human Evolution
Gregory Cochran and Henry Harpending, 2009
A companion to Marlene Zuk's "Paleofantasy".
Science, at its best, destroys comfortable ideology, and opens your eyes to the world around you.
"Evolution" by natural selection is not just a Pavlovian bile stimulator for creationists, it is a tool to understand how lifeforms, especially human lifeforms, work. Natural selection is a quantifiable process - it has a large element of chance, but repeated chance can have certain results: water fills bowls, air fills rooms. Natural selection starts with unpredictable chance mutations, but amplifies or deletes them by a repeatable process.
Four takeaways from the book:
1) On average, a mutation with 1% selective advantage has a 2% chance of survival, and in time, spreading throughout the gene pool. The greater the advantage, the faster the spread. Advantage is the benefits minus the drawbacks - a gene might improve your production of progeny by 20%, and increase your chances of death by by 15%; a net gain of 5% means it will spread fast. The book uses the example of Ashkenazi Jews, who have a genetic mutation that leads to increased intellect and increased Tay Sachs, as an example.
2) Changing circumstances drive strong selective pressures. Gathering berries in a temperate climate selects for different genes than hunting game in an ice age. If there are big changes in the environment (such as crowding and sharing diseases), the selection pressures are very strong and changes can spread in a few generations.
3) More food (agriculture) means more people, more people means more mutations to feed into the selection mill, ergo, faster evolution.
4) Disease survival in social groups can evolve genes rapidly. Native Americans adapted to syphilis, Europeans adapted to smallpox, Africans adapted to malaria, and the diseases adapted to each group. Released into unadapted populations, the diseases can wipe out whole populations, because mutation does not have time to produce useful alleles, and selection does not have time to spread them.
Interbreeding between human populations can sometimes break the dependencies that gene complexes need to work, but over time working groups will transfer, and new and better groups will assemble out of the mixed components. A lot of that going on now.
The book is potentially aggravating. If you are a politically correct American Democrat, these two Utah boys will get your goat a few times. But reading is not for the thin skinned - if you want preprocessed ideologically safe input, confine yourself to NPR or FOX, and walk through life with blinders.