Coastal waters were an oxygen oasis 2.3 billion years ago

Despite being ripe for complex life, it took another 1.5 billion years for oxygen-hungry animals to evolve

fossil eukaryote

OXYGEN OASIS  Oxygen was abundant enough for complex life-forms such as this 1.4-billion-year-old fossilized eukaryote to thrive around 2.3 billion years ago, new research suggests. The expansion and diversification of eukaryotes nevertheless only came hundreds of millions of years later.

Andrew Knoll/Harvard University

Earth was momentarily ripe for the evolution of animals hundreds of millions of years before they first appeared, researchers propose.