Mastodawn

anatole Feb 21, 2023

Where have people lived?
Let's #map human migrations 🧵

Here is a world map with the North Pole at center.
Africa, harbouring the start of #humans, is at the top left and South #America at the far right.
Numbers represent massive #settlements thousand years ago.

Notice that:
- Europeans were overwhelmed 50,000 to 40,000 years ago; #grandRemplacement
- the first massive migrations to America did not progress much south of Rio Grande;
- no big migration shows above current Antarctic temperatures.

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anatole

Definitions 🧵:
A #haplogroup is a combination of #alleles that tend to be inherited together.
An #allele is a variation of the same sequence of nucleotides at the same place on a DNA molecule.

#Haplogroups pertain to a single line of descent. As such, individual membership of a haplogroup relies on a small proportion of the #genetic material possessed by that individual.

Mothers pass on mitochondrial #DNA unmixed to all their children; so the #ancestry can be traced along the maternal line.

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anatole Feb 21, 2023

Men, not women, carry a Y chromosome, and it’s passed down father-to-son. Because the Y chromosome isn’t split and shuffled each generation, it’s a key signature for #ancestry.

In human #genetics, the #haplogroups most commonly studied are Y-chromosome (Y-DNA) haplogroups and mitochondrial DNA (mtDNA) haplogroups, each of which can be used to define genetic #populations.
mtDNA or Y-DNA changes only by chance mutation at each generation with no intermixture between parents’ genetic material.