This website in an attempt to explain DNA diversity that allows us to identify "older" genomes from more "recent" ones, says the following:
"There are parts of your (our) genome where random mutations won’t generally kill you. Random mutations tend, therefore, to accumulate there. Since have some pretty decent estimates for how often random mutations occur, comparing the mutations in two different populations lets us estimate how long ago they split. For example, let’s suppose you get one random mutation per hundred years, and we’re comparing two populations that split 300 years ago and haven’t seen each other since. Population A should have gotten 3 mutations during that 300 years, and Population B should have gotten 3 mutations. So if we look at a third population, C, and find that they have 5 mutations that they don’t share with A or B, then we conclude that C split off from some ancestral population 500 years ago. We can reconstruct this as: 600 years ago, there was a group called ABC, but 500 years ago, it split into Group AB and Group C. 300 years ago, Group AB split into Group A and Group B."
Sounds great, so clear, so logical... but... This is a typical explanation for diversity in Africa vs. out of Africa and to put it bluntly, it is Wrong!!. And this is why:
It says there was an ancestral group, ABC which split 500 years ago into AB and C. Since the split, group C accumulated 5 mutations. And group AB split 300 years ago. Each sub group, A and B, accumulated 3 mutations each, which made them different. So as C has 5 mutations but A and B only 3 each, C is "older" than A or B. Did you see the mistake in this logical explanation?
The error is that although they postulate a random mutation every 100 years, the group AB which split from ABC 500 years ago did not accumulate any mutations from then until the split of A and B 300 years ago.
AB group did not accumulate a single mutation over 200 years, but C did, it added 2.
Then, A split from B, and both of them kept on mutating at 1 mutation every hundred years. Final score: C = 5 mutations and A & B only 3.
Actualy AB would have accumulated mutations over those 200 years, different mjtations from those of C. In fact all groups A, B and C would have accumulated 5 mutations over those 500 years.
All humans are equally ancient, we all carry the original DNA, and after we split into separate groups, our random mutations led us to split apart a bit more, but we all have roughly the same amount of mutations, unless, of course these mutations are not random, but are mobilized by selection, but that will be discussed in another post.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2018 by Austin Whittall ©
No comments:
Post a Comment