LIFE × EVOLUTION

Flight, Then Sonar

~52 million years ago

Phanerozoic · Cenozoic · Paleogene · Eocene

A mammal with a membrane between elongated fingers, a claw on every one of them, and an inner ear too small to have heard its own echoes. The wing was already finished; the sonar was not. Its relatives, a few million years later, were hunting by listening.

Why it matters

Bats are the fourth and last origin of powered flight in animals, and this fossil settles an order that could not be settled any other way. Wing first, sonar second, and the two abilities that make a bat a bat were assembled one at a time rather than together.

Dating & uncertainty

A Wyoming fossil of 52 million years ago has fully formed wings and an inner ear too small for echolocation, which argues that flight came first. The order is still debated, and some hypotheses have sonar evolving before or alongside the wing.

Sources

1. Simmons et al. (2008), Nature · Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation
2. Speakman (2001), Mammal Review · The evolution of flight and echolocation in bats: another leap in the dark
3. Anderson & Ruxton (2020), Mammal Review · The evolution of flight in bats: a novel hypothesis

Earth history as one day

23:43:3016 min 30 s before midnight

if Earth’s 4.54 billion years were compressed into a single day