It is a branching, converging, diverging network of ancestral relationships that reflects millions of individual decisions about where to live, whom to reproduce with, and how to respond to the environmental, social, and historical pressures of each successive generation.

The genomic tools now available to researchers can, for the first time, begin to reveal some of the structure of that network in the deep human past.

What those tools are revealing is not simplicity but complexity — not a single clean origin story but a many-stranded web of ancestral connections that links the people of Lagoa Santa to people in Asia, to people in Australia and New Guinea, and ultimately to all of humanity.

That is, in the end, the most important thing the Population Y signal tells us.