The Friends of Charles Darwin

BBC: Bat fossil solves evolution poser

A fossil found in Wyoming has resolved a long-standing question about when bats gained their sonar-like ability to navigate and locate food.

They found that flight came first, and only then did bats develop echolocation to track and trap their prey.

A large number of experts had previously thought this happened the other way around.

To me, it seems obvious (always a dangerous word when talking about evolution) that bats must have been able to fly before they evolved echolocation. Echolocation would seem to have only limited use for ground-based mammals, otherwise more mammals would surely have evolved the capability.

I was curious to know, therefore, why so many experts thought that bats' echolocation must have evolved before flight. I thought it might be because, according to the above BBC article, all bats echolocate, so, unless echolocation evolved independently several times over (which is perfectly possible), it must have evolved in a (presumably early) common ancestor. It turns out that that there was simpler explanation as to why so many experts believed echolocation evolved before flight: until this new fossil, Onychonycteris finneyi, was discovered, another species, Icaronycteris index, had, for over 40 years, been regarded as the oldest known bat—and Icaronycteris index could echolocate.

I was also surprised to learn that all bats echolocate. I had assumed that fruit bats don't. It turns out they do have the capability, but it is greatly reduced—as is also the case with vampire bats. Echolocation in these bats, it seems, could be seen as vestigial, and might be on the way out.

Interesting stuff.

I like bats.