Million‑year divergence still allows interbreeding

David Reich's preprint outlined in the article proposes that a modern human expansion ~300,000 years ago mixed with deeply diverged archaic lineages, implying that groups separated for on the order of a million years could still produce viable offspring. That reframes assumptions about how long genetic separation undermines sexual compatibility and invites study of mate choice, fertility genetics, and cultural framing of ancestry. — If long‑diverged human lineages can interbreed, it undercuts simplistic biological narratives about deep separations and has implications for how ancestry, race, and reproductive biology are discussed in public policy and culture.