Mammals inherit the world
Empty niches fill within ten million years
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The Bighorn Basin in Wyoming provides one of the most continuous sequences through the transition. Mammalian body size increases tenfold within a few hundred thousand years of the boundary, and all modern orders are established by the early Eocene. Molecular data suggest many lineages had diverged before the impact but stayed small and inconspicuous — it was ecological opportunity, not new genetics, that triggered the explosion. It is the clearest demonstration in the fossil record that who dominates is decided as much by who disappeared.
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After the asteroid, no large land animals were left. Mammals, which had been small and nocturnal for 160 million years, suddenly had the world to themselves. In just ten million years they became everything from bats to whales to horses.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org