BeijingTooth proteins from 400,000-year-old Homo erectus teeth can reveal ancestry that DNA cannot.
Chinese researchers matched a protein variant to Denisovan genomes, suggesting the two species interbred — evidence unreachable by ancient DNA.
Over 20% of some Philippines populations carry the variant, the study found.
Sources: Ars Technica
WHY PROTEINS OUTLAST DNA
DNA is a fragile double helix held by hydrogen bonds; it shatters into unreadable fragments after roughly 1 million years even in cold conditions, and far sooner in the tropics. Proteins are tougher — especially enamel proteins locked inside tooth crystal — and can survive 2 million years or more.
HOW THE METHOD WORKS
Enamel is 96% mineral, but the remaining sliver holds proteins like amelogenin and enameloid. A pinhead of tooth is dissolved, the peptides are sequenced by mass spectrometry, and single amino-acid substitutions are mapped back to genes — letting researchers infer the underlying DNA without ever recovering it.
THE DENISOVAN PUZZLE
Denisovans were identified in 2010 from a single finger bone in a Siberian cave. For a decade their fossil record was almost nothing — a few teeth, a jawbone from Tibet — yet their DNA lived on in modern humans across Asia and Oceania. Paleoproteomics is now filling in the bodies that go with the genome.
THE LEGACY IN LIVING GENOMES
Denisovan DNA didn't vanish — it sits inside billions of people today, concentrated in the populations whose ancestors crossed paths with them in Sundaland and Sahul.
THE EPO1 GENE
The most famous Denisovan inheritance is EPAS1, a variant carried by ~80% of Tibetans that regulates hemoglobin response at altitude. It is the clearest case of an archaic gene being kept by natural selection because it solved a problem modern humans couldn't.
WHY THIS REWRITES THE TREE
If Homo erectus — the species that left Africa 1.8 million years ago — interbred with Denisovans, then archaic gene flow runs deeper than the Neanderthal–sapiens crossings of 50,000 years ago. The human family tree is less a tree than a braided river.