What happened
Kyoto University researchers rebuilt the evolutionary family tree of blood cells and found that key immune cells trace back to single-celled ancestors from about 700 million years ago. Macrophages, the cells that engulf invaders, most closely resembled those ancient microbes, and a gene called FOS links the lineage all the way back.
What I love about this is the picture of complexity it paints. Modern blood did not appear from nowhere. Early animals reused genetic toolkits inherited from single-celled life, then branched mast cells, T cells, red blood cells, and B cells off that foundation over hundreds of millions of years.
Complexity tends to be remixed, not invented. The same method may help trace the deep origins of diseases like cancer. A good reminder that we are walking archives of an extremely long experiment.
Source
Reported by Scientists Discover Ancient Single-Celled Ancestors Still Live On in Your Blood via sciencedaily.com, published May 27, 2026.