Treasure trove of ancient genomes helps recalibrate the human evolutionary clock

Just like adjusting a watch, the key to accurately telling evolutionary time is based upon periodically calibrating against a gold standard.

Scientists have long used DNA data to develop molecular clocks that measure the rate at which DNA changes, i.e., accumulates mutations, as a premiere tool to peer into the past evolutionary timelines for the lineage of a given species. In , for example, molecular clocks, when combined with fossil evidence, have helped trace the time of the last common ancestor of chimpanzees and humans to 5-7 million years ago, and contributed to the recent 'out of Africa' theory for a great human migration event 100,000 years ago.

To improve the modeling and reading of the branches on the human tree of life, authors Francois Balloux et al, compiled the most comprehensive DNA set to date, a new treasure trove of 146 ancient (including Neanderthal and Denisovian) and modern human full mitochondrial genomes (amongst a set of 320 available worldwide). Mitochondrial DNA (mtDNA) is a precious resource for evolutionary scientists, because they have a high mutation rate, and unlike genomic DNA, are only maternally inherited.

Now, by using a variety of sophisticated calibration techniques, the authors have improved the accuracy of using mtDNA as a by recalibrating the human . They showed that a molecular clock calibrated with ancient sequences was far more accurate than the traditional ones based on archaeological evidence. With this new recalibration, scientists can now trace back, with greater accuracy than ever before, the first 'Eves' of the many migrations leading to the colonization of the earth by anatomically modern humans.

"The recent possibility to generate high-quality genome sequences from ancient remains represents an amazing progress in our ability to accurately reconstruct the past history of many species, including our own," said author Adrien Rieux.

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Citation: Treasure trove of ancient genomes helps recalibrate the human evolutionary clock (2014, October 8) retrieved 18 September 2019 from
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Oct 08, 2014
I wonder if the research quoted below has relevance to human studies as well?
"The genome and the information it contains about our ancestry and evolution is huge," said lead author Mark Statham, an assistant project scientist with the UC Davis Veterinary Genetics Laboratory. "If you're only looking at what your mother's mother's mother did, you're only getting a small portion of the story."...Conventional thinking based on maternal genetics suggested that red foxes of Eurasia and North America composed a single interconnected population across the Bering land bridge between Asia and Alaska. In contrast, this new research shows that the red foxes of North America and Eurasia have been almost entirely reproductively isolated from one another for roughly 400,000 years...."
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Oct 09, 2014
@MikPetter: Good question and nice reference!

Certainly the nuclear genome (where the Y chromosome sits) is used too. And the Y chromosome is also more sensitive to elapsed time than the rest of the genome, since it is similarly small and unpaired.

But the Y chromosome doesn't reach as broad and deep I think (implied by the article here), since only half the population has a copy vs 200 - 400 mitochondrial copies in an egg cell. (I think, extrapolated as what usual somatic cells IIRC has.) And you have to sequence more, more or less the whole nuclear genome at a guess, while the larger genome has more errors in total (lose-lose).

Incidentally, the fact that foxes has been isolated through the Bering Strait has some implications for the difficulty but also success (small groups enough) for our ancestors to migrate that way.

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