Origin: A Genetic History of the Americas

scenario for the origins of Native Americans based on current genetic data
—remember that the labels we attach to the populations in all images to
follow artificially neaten an extraordinarily complex and tangled family
tree.
We are using a dozen or so genomes across 20,000 years of time to
attempt to understand the movements, matings, births, and deaths of untold
numbers of people. What is quite amazing about paleogenomics is how well
it works: Each person’s genome is a reflection of thousands of ancestors,
allowing us to understand human narrative on a grand scale.
But as you read this genetic chronicle, please do not lose sight of the
dignity of the human beings who lived this history and the rich complexity
of individual existences that are lost in the telling. The story I tell here is
akin to reconstructing a person’s entire life by stitching together the photos
they posted on Instagram. Not inaccurate, necessarily, just… incomplete.
The images in this chapter present an overview of the history genetics tells
us about the first quarter of our story: the formation of the gene pool that
gave rise to Native Americans between about 43,000 and 25,000 years ago.
Think of them as our roadmap, a way to orient ourselves in the confusing
twists and turns of migrations and population formation. Our journey
through history in this chapter is aiming for the group or groups that were
directly ancestral to Native Americans. To get there, we will have to tell the
story of the two populations that served as their antecedents: the ancestral
East Asians and the Ancient Northern Siberians.
I want to begin this history about 36,000 years ago with the emergence
of the ancestral East Asian population, but to get there, I must first move
further back in time. Here is a brief chronological sketch of the events
leading up to that point: