Your Blood May Contain an Evolutionary Relic Older Than Animals Themselves

A Kyoto University-led study traces blood cell origins back about 700 million years.

Researchers compared gene-expression data across animals and unicellular species to map the evolutionary roots of blood cells.

The findings suggest blood cells evolved from ancient macrophage-like scavenger programs, not from a brand-new animal-only system.

The Fos gene helped reveal this connection across humans, zebrafish, sea squirts, and sea urchins.