When the asteroid smashed into Earth 66 million years ago, it wiped out the fiercest, strongest creatures on Earth–the dinosaurs. So how exactly did our tiny, furtive ancestors thrive in the aftermath of an apocalypse?

by PROF STEVE BRUSATTE

ILLUSTRATION: MAGIC TORCH

The supercontinent Pangaea began to break apart in the early Jurassic, around 200 million years ago

When the asteroid smashed into Earth some 66 million years ago, as visualised here, it altered the path of evolution for the planet’s species

D uringthe Triassic, some 225 million years ago, two types of animals went their separate ways.

They were both born on the supercontinent of Pangaea, the single slab of land that stretched from the North Pole to the South. Their fates would be different, but forever intertwined. One group was destined for grandeur, and before long, their aeroplane-sized bodies thundered across the land. Dinosaurs. The other group was relegated to the shadows to bide their time.

Mammals. Us, our distant ancestors.

Fast-forward some 160 million years, through the Jurassic and to the end of the Cretaceous. Temperatures spiked and crashed, sea levels rose and fell, and the supercontinent became the many continents of today. Through all of this time, dinosaurs and mammals lived together, but followed their own paths. No mammal ever got larger than a badger, as they were held in check by the dinosaurs. Conversely, the smart and furry little mammals kept dinosaurs from the small-bodied niches, so there never was a miniature T. rex or Triceratops. Like ships passing in the night, the dinosaurs and mammals both diversified, claiming separate realms as their own. Dinosaurs ruled the forests and plains by day, mammals the brush and underground in darkness.

Then, in an instant, everything changed. Sixty-six million years ago, a sudden disaster reshaped the world, and within days, months and years, it upended an evolutionary status quo that had persisted for more than 100,000 millennia. The dinosaurs – except for a few peculiar species with wings and feathers, which became today’s birds – couldn’t cope, and they went extinct.

Many mammals felt the pang of death, too, but some managed to endure. From these plucky survivors, the next great dynasty of Earth history would blossom.