A Kyoto University study reconstructs a 700-million-year blood cell family tree by comparing gene expression across species and unicellular organisms, showing modern blood cell development mirrors ancient evolutionary steps.

Macrophages emerge as the blood cell type most closely tied to unicellular gene expression, suggesting macrophage-like cells were the primordial blood cells at the origin of multicellular animals.

Researchers traced the FOS gene back to a 700-million-year-old single-celled organism, aligning with the emergence of multicellular animals and the origin of blood cells.

The authors present a new method for tracing gene-expression lineage across diverse organisms, with potential to illuminate the evolutionary origins of diseases like cancer and guide future therapies.

This method could help understand the evolutionary roots of diseases such as cancer and potentially inform new treatment approaches.

Publishers and researchers anticipate the method will aid in exploring the evolutionary origins of cancer and potentially lead to novel therapies.

Researchers emphasize broader implications for understanding cancer and other pathologies through evolutionary-informed views on blood and immune cell development.

The findings were published in the Proceedings of the National Academy of Sciences on May 25, 2026, underscoring the deep-time genetic legacy carried through blood and immune cells.

Advances in transcriptome profiling and computational phylogenetics enabled cross-species comparisons that were previously limited by data availability.

The study links hematopoietic differentiation in vertebrates to ancestral unicellular programs, offering insights into immunity, disease pathogenesis, and potential therapies.

Publication details: Animals expand the evolutionary legacy of unicellular ancestors in blood cells, in Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.2528110123).

Team leader Hiroshi Kawamoto and first author Yosuke Nagahata stress the emotional and scientific significance of tracing this lineage, linking current blood cells to distant unicellular ancestors.