DNA barcodes and genetic diversity in humans

  • #1
jim mcnamara
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Very short and general precis: Analyzing the 'barcode' gene in mitochondria (big data source) has found that most current animal species have comparatively tiny genetic diversity, humans included. Based on the data, the conclusion is modern human genetic diversity is low, and modern humans as a species are about 200,000 years old. The same holds true for many of the other animal species in the database, 200,000 years.

Comment: hmmm. If this study holds water it means that most of the extant animals and early humans all underwent some kind of evolutionary change 200,000ya. This is sure to arouse lots of skepticism.

Background:
https://en.wikipedia.org/wiki/DNA_barcoding
Popular Science:
https://phys.org/news/2018-05-special-humanity-tiny-dna-differences.html
Paper:
"Why should mitochondria define species?" Human Evolution
DOI: 10.14673/HE2018121037
This DOI link is broken for now. I cannot get to the original. Expect it will be fixed shortly.
 
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  • #2
Bystander
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Comment: hmmm. If this study holds water it means that most of the extant animals and early humans all underwent some kind of evolutionary change 200,000ya. This is sure to arouse lots of skepticism.
..., or not. Methinks there could be a bit more to the thesis/hypothesis than meets the eye. Not a fan of "punctuated equilibrium," up until this time/point, but may have to backtrack on that assessment.
 
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  • #3
jim mcnamara
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@Bystander - punctualism fits a lot of the data we have. Its is the 200Kya boundary I have some issues with.

My issue with this paper is plant geography and the statement of many animal species species from divergent phyla having evolved all 200Kya. Plants should also display this feature at least to some extent. Schizaea - the curly grass fern, exists natively in two places: the dwarf pine forest in the New Jersey Pine Barrens and in one pine forested valley in the Ural mountains. The best possible explanation is not the 'constipated bird theory of plant distribution', but Plate Tectonics. Does this mean the species has persisted for 60 million years? It's possible - there are cycad fossils of extant species that date from the Eocene.

And yes it is hard to claim they are the same species. They could be genotypically unrelated and phenotypically identical. Which is also a stretch. But Plate Tectonics does explain the current distributions of the phyla of many plants and animals.

If they perform the same experiment on barcode data from plant species I'll be willing to buy the 200Kya boundary. Currently we are 'stuck' on choosing a suitable definition - candidate gene: http://www.pnas.org/content/106/31/12794.full?sid+38cee406-d425-4f58-8edc-bbcb2ac34bad
 
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Its is the 200Kya boundary I have some issues with.
We had ice ages, vulcanic eruptions and such relative frequently during that margin of error of that 200k year to manage (and eventually: break up) population sizes.
My issue is with the original statement (of the popularized version of the paper what I could google up so far) instead.
It is textbook biology, for example, that species with large, far-flung populations -- think ants, rats, humans -- will become more genetically diverse over time.
I'll try to dig up the original paper tomorrow, but I just can't help it: such statements makes it feel like a really bad joke.
 

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