A battle against arsenic toxicity by Earth’s earliest complex life forms | Nature Communications
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The toxicity of arsenic has challenged life for billions of years, but the timing of when complex organisms first evolved strategies to cope with this threat remains elusive. Here, we study 2.1-billion-year-old (Ga) Francevillian macrofossils, some of Earth’s earliest complex life forms, to establish their biogenicity and to ascertain how they managed arsenic toxicity. The studied specimens thrived in low-arsenic marine waters, yet displayed strikingly high levels of arsenic, which was actively sequestered in specialized compartments in their bodies to mitigate toxicity. Upon their death, arsenic was released and incorporated into pyrite nuclei. The patterns observed in the fossils are distinct from abiotic concretions but similar to some seen in later eumetazoans, reinforcing their biological affinity. Our findings highlight that early complex life faced significant arsenic stress, even in low-concentration marine environments, which prompted the development of essential survival mechanisms. Arsenic incorporation into pyrite nuclei reveals that the 2.1-billion-year-old Francevillian biota actively detoxified arsenic by sequestration in specialized body compartments.

The toxicity of arsenic has challenged life for billions of years, but the timing of when complex organisms first evolved strategies to cope with this threat remains elusive. Here, we study 2.1-billion-year-old (Ga) Francevillian macrofossils, some of Earth’s earliest complex life forms, to establish their biogenicity and to ascertain how they managed arsenic toxicity.

The studied specimens thrived in low-arsenic marine waters, yet displayed strikingly high levels of arsenic, which was actively sequestered in specialized compartments in their bodies to mitigate toxicity. Upon their death, arsenic was released and incorporated into pyrite nuclei. The patterns observed in the fossils are distinct from abiotic concretions but similar to some seen in later eumetazoans, reinforcing their biological affinity.

Our findings highlight that early complex life faced significant arsenic stress, even in low-concentration marine environments, which prompted the development of essential survival mechanisms.