How *Fallen Angels* Polluted the Human Race. DNA study finds many genetic mutations are rare and recent

Scientists look at a broad sample of human DNA and get a snapshot of how dramatically we've changed in the last few thousand years.

Human DNA contains myriad individual differences that influence a host of traits, be they eye color or the ability to digest milk. Now a study shows that most of those tiny genetic variations are rare — and they arose in the very recent history of our species.

Joshua Akey, a geneticist at the University of Washington in Seattle, led a consortium of scientists who examined the DNA of 4,298 European Americans and 2,217 African Americans. Limiting their analysis to the parts of the genome that contain instructions for making proteins, the study authors found more than 1 million sites where the building blocks of DNA — the nucleotides known by the letters A, C, G and T — varied in at least one of the subjects.

The scientists were even able to estimate the age of variations based on how rare or common they were — and found that about 73% of the mutations had occurred in the last 5,000 to 10,000 years.

The percentage of rare — and therefore recent — mutations was greater in European Americans than African Americans, the team reported. That fits with the history of Homo sapiens: The ancestors of Europeans went through explosive population growth when they left their homeland in Africa tens of thousands of years ago.

[link to www.latimes.com]