On Jul. 1, 2025, an international team of researchers led by by the Université de Poitiers and Cardiff University announced finding that ancient complex life forms, called eukaryotes, stored arsenic inside special compartments within their cells, a strategy that helped neutralise the toxic poison.

Using advanced X-ray technology, the international team was able to detect and map arsenic within 2.1-billion-year-old fossils from the Francevillian Basin in Gabon.

The arsenic found in the fossils was not due to later contamination but part of a biological response to environmental stress, according to the team.

This is revealed by distinct patterns formed from the arsenic preservation process in the fossils when compared to structures left by non-living mineral structures; it is further evidence the fossils were once complex living organisms with more advanced cells, they argue.

Their study, published in Nature Communications, reshapes current understandings of how early life faced environmental challenges, highlighting the critical role adaptation played in the evolution of life.