Monday, March 16, 2015

Evolution rates and DNA mutation clocks

Article: DNA mutation clock proves tough to set

I don't want to get into the weeds about this. I have seen some triumphalism among the more Bible-believing sites I visit that this disproves the possibility that everything evolved without any "outside" interference [read: God]. Or at least calls into a completely atheistic view of evolution.

I am not so certain.
Mathematicians keep refining π even though they know it to more than 12 trillion digits; physicists beat themselves up because they cannot pin down the gravitational constant beyond three significant figures. Geneticists, by contrast, are having trouble deciding between one measure of how fast human DNA mutates and another that is half that rate.
Or another way of putting that, "and another that is twice that rate."

Mutations provide the raw material for evolution. Red, blond and brown hair colors are the result of mutations. The ability in adult humans to digest milk and milk products is the result of a mutation.
The rate is key to calibrating the ‘molecular clock’ that puts DNA-based dates on events in evolutionary history. 
How fast genes mutate determine how fast evolution can happen. If the rate is too slow, then life could not have originated and evolved into it current diversity in the time allowed.
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 world. 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. 
"Slow clock." "Fast clock." "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.
Evolution works on the gene variations that are present in a population. Mutations provide those variations. One cannot speed up evolution in a population that does not have sufficient variations to change.

"Hedging their bets." Using different estimates to fit the data is the wrong way round of doing things. One takes the data and have it drive the estimates, guesses, and hypotheses.

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