Life invents sex
A red alga on Somerset Island is the oldest evidence
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Bangiomorpha pubescens, found in the Hunting Formation on Somerset Island in Canada and dated to around 1.05 billion years, is the oldest fossil showing differentiated sex cells. It is simultaneously the oldest fossil assignable to a living group — it is a red alga, close kin to modern Bangia. Sexual reproduction is expensive: you pass on only half your genes, and you have to find a partner. That it nonetheless dominates among complex organisms is explained by recombination purging harmful mutations and allowing beneficial variants to combine. Without sex, evolution is limited to whatever mutations a single lineage manages on its own.
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Until now all life had made copies of itself. Then some organisms began mixing their genetic material with another. Every offspring became slightly different from its parents — and evolution suddenly had far more to choose between.
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Part of Terra Saga — the story of Earth on a timeline. terrasaga.org