🌍 How early organisms overcame arsenic 2.1 billion years ago

Long before the appearance of plants or animals, primitive multicellular organisms had developed an effective strategy to survive arsenic, a notoriously deadly poison. A recent study reveals that these life forms stored this toxic element in specialized cellular compartments.


The studied fossils come from the Franceville Basin in Gabon, a site already known for containing some of the oldest traces of multicellular life. Using X-ray microtomography analyses, researchers observed that arsenic was integrated into the very structure of the fossilized cells, rather than being present due to contamination.

This adaptation likely emerged during a period marked by increasing oxygen levels in Earth's atmosphere. This change promoted the oxidation of arsenic into arsenate, a particularly toxic form because it mimics phosphate, which is essential for life. To survive, these eukaryotes had to differentiate between these two elements at the cellular level.

The study shows that these organisms did not survive the volcanic activity that disrupted their environment. However, their arsenic management strategy may have been reinvented multiple times throughout the history of life, demonstrating a remarkable capacity for adaptation.

How did early organisms survive arsenic?

The analyzed fossil eukaryotes stored arsenic in isolated compartments within their cells. This process allowed them to limit the toxic effects of arsenate by preventing it from disrupting essential cellular functions.

This strategy implies a certain complexity in cellular organization, proving that even in this distant era, life displayed biochemical ingenuity. By distinguishing between arsenate and phosphate, these organisms reached a major milestone in their evolution.

This discovery illustrates the idea that adaptation to extreme conditions is not the exception but rather a constant in evolution.

Why did these organisms disappear?

Their extinction appears linked to a major environmental upheaval caused by renewed volcanic activity. This disruption altered water chemistry, reduced oxygen levels, and created an overly hostile environment.

Despite their resistance to arsenic, these organisms could not withstand all these changes. Their disappearance shows the limits of biological adaptation, even when facing a previously overcome threat.

However, this extinction made way for other, better-adapted lineages. It is part of a cycle of emergence, crisis, and renewal that characterizes the history of life on Earth.