LIFE × EVOLUTION

Flight, Then Sonar

~52 million years ago

Phanerozoic · Cenozoic · Paleogene · Eocene

A mammal with a membrane stretched between elongated fingers, a claw on each of them, and an inner ear too small to have heard its own echoes. The wing was already finished; the sonar was not. Its close relatives of the same epoch hunted by listening.

Why it matters

Bats are the fourth and last animal group in which powered flight appeared, and until this fossil came to light the bones had said little about the order in which they acquired the two abilities that define them. It tips the argument towards the wing first and the sonar afterwards, against the rival accounts that reverse that order or have both arrive together.

Dating & uncertainty

A 52-million-year-old fossil from Wyoming has fully formed wings and an inner ear too small for echolocation, which argues that flight came first. The order is still debated, and rival hypotheses have the sonar appearing before the wing or alongside it.

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