Genome complexity: Mutation rate uncertain (Introduction)

by David Turell , Tuesday, June 16, 2015, 15:15 (3236 days ago) @ David Turell

Trying to estimate human mutation rates by comparing genomes results in very uncertain estimates of rates. This puts the estimates of when ancestors branched off in great doubt:-http://www.nature.com/news/dna-mutation-clock-proves-tough-to-set-1.17079-"A slower molecular clock worked well to harmonize genetic and archaeological estimates for dates of key events in human evolution, such as migrations out of Africa and around the rest of the world1. But calculations using the slow clock gave nonsensical results when extended further back in time — positing, for example, that the most recent common ancestor of apes and monkeys could have encountered dinosaurs. Reluctant to abandon the older numbers completely, many researchers have started hedging their bets in papers, presenting multiple dates for evolutionary events depending on whether mutation is assumed to be fast, slow or somewhere in between.-"Last year, population geneticist David Reich of Harvard Medical School in Boston, Massachusetts, and his colleagues compared the genome of a 45,000-year-old human from Siberia with genomes of modern humans and came up with the lower mutation rate2. Yet just before the Leipzig meeting, which Reich co-organized with Kay Prüfer of the Max Planck Institute for Evolutionary Anthropology, his team published a preprint article3 that calculated an intermediate mutation rate by looking at differences between paired stretches of chromosomes in modern individuals (which, like two separate individuals' DNA, must ultimately trace back to a common ancestor). Reich is at a loss to explain the discrepancy. “The fact that the clock is so uncertain is very problematic for us,” he says. “It means that the dates we get out of genetics are really quite embarrassingly bad and uncertain.'”