"As bats are the only mammals known to have evolved true powered flight, our findings point to Europe as the most likely place where mammalian powered flight first evolved," Teeling added.

The team also analyzed the fossil bat Vielasia, which sits on the oldest branch of the family tree. Its placement suggests echolocation had already emerged close to the start of bat evolution.

Both features therefore appeared before modern bat groups began to diversify.

How did researchers settle the debate?

Building the family tree proved difficult. Different parts of bat genomes preserve conflicting evolutionary signals, likely because early bat lineages exchanged genes.

The team found, however, that part of the X chromosome preserved an especially clear record. That signal allowed scientists to resolve relationships that had been disputed for decades.

"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.

What did the ancestor's genome reveal?

Beyond tracing origins, the team computationally reconstructed the genome of the common ancestor of all living bats. That reconstruction offers a window into the genetics of one of the earliest flying mammals.

The dataset gives researchers a tool for studying the genetic changes behind flight, echolocation, longevity and disease resistance.

"We combined state-of-the-art DNA sequencing and computational methods to generate and compare these genomes and identify the genes they contain," said Professor Michael Hiller of the Senckenberg Research Institute in Frankfurt.

Why do bats matter beyond biology?

Many bats live far longer than other mammals of similar size. They also resist viruses that devastate humans, including those linked to Ebola and COVID-19.

The new genomic resource could eventually help scientists probe the genetic basis of ageing, immunity and viral resistance in humans.

"Bats constantly surprise us. They are one of evolution's greatest experiments," said Professor Sonja Vernes of the University of St Andrews. "This extraordinary genomic resource, the culmination of years of international cooperation of Bat1K, is finally allowing us to understand how their remarkable biology evolved."

What comes next?

The study sequenced 42 new chromosome-level genomes, drawing on decades of fieldwork from New Zealand to Madagascar. The team hopes to use the same approach to revisit unresolved questions in mammal evolution.

Funding came from the European Research Council, Science Foundation Ireland and the Irish Research Council, alongside international partners.