Bats are the only mammals that can fly, and they use sound to find their way at night. They make up about one-fifth of all mammal species on Earth and help keep ecosystems in balance. Where they first came from, though, has long been an open question.
A comprehensive study now offers evidence that bats originated in Europe in the Late Paleocene, about 65 to 60 million years ago.
The work comes from the Bat1K consortium, a team of 137 researchers in 64 countries, co-founded by Professor Emma Teeling of University College Dublin. The group aims to sequence the genomes of all living bat species. For this study, they used 103 bat genomes, including 42 highly complete ones covering all 21 recognized bat families. They combined those genomes with data from 44 fossil bats, producing the largest evolutionary reconstruction of bats so far.
The results point to Europe as the starting place. From there, descendants moved into Africa, then spread into the Americas, Asia and Australia. That spread, the researchers say, produced the diversity of bats we see today. Teeling called the result "a robust phylogenetic tree," a family tree others can use to study how bats' unusual traits evolved.
The study also looks at when those traits appeared. Fossils of Vielasia, one of the earliest known branches of the bat family tree, suggest that echolocation, the use of sound to navigate, evolved near the beginning. Powered flight and echolocation both seem to have been in place before modern bats split into many groups. That double advantage may help explain why bats succeeded worldwide.
"The approach we used to model the evolution of fossil and living species together can do what other methods cannot: identify the oldest group of fossil bats while taking the genomic data into account, and uncover when and where bats originated," said Professor Liliana M. Dávalos of Stony Brook University.
By reconstructing the genomes of ancient bat ancestors, scientists can now look at a genetic outline of what may have been the first flying mammal. That may help them study flight, echolocation and long life at the molecular level.
Bat family relationships have been hard to pin down. Different parts of the genome often tell different stories, likely because genes mixed between early groups. The team found that one chromosome region kept a clear signal, which helped settle decades of debate.
If bats first evolved in Europe, that also changes the story of mammals more broadly. Europe was not only a birthplace for familiar groups such as primates and hoofed animals. It may also have been home to the only flying mammals, which later spread across almost the whole world.