Scientists discover ancient single-celled ancestors still live on in human blood, revealing a 700-million-year evolutionary link hidden inside the immune system. Researchers at Kyoto University traced modern blood cells back to primitive unicellular organisms that existed before complex animals appeared on Earth. The study found macrophages and immune genes like FOS still carry ancient biological patterns today.

You probably don't think much about the blood running through your veins on a daily basis.

Scientists have uncovered evidence that human blood and immune cells may have evolved from ancient single-celled organisms nearly 700 million years ago. Researchers at Kyoto…