Genes inherited from long-extinct human ancestors may be more common than thought, suggesting a Homo sapiens origin story with more than a few evolutionary one-night stands.

The latest findings involve genes from Denisovans, a recently-discovered member of the Homo genus who lived in central and eastern Asia until 40,000 years ago. Denisovans, humans and neanderthals last shared a common ancestor about 1 million years ago.

Earlier research found lingering Denisovan traces in genomes of people from Oceania. Now they’ve been found in southeast Asia, too.

“We haven’t been a very exclusive species, w...