A new study is reshaping scientists’ understanding of bat evolution, suggesting that bats most likely originated in Europe during the late Paleocene, approximately 65 million to 60 million years ago.

Researchers have debated for decades where bats first appeared. Africa, Asia and North America have all been proposed as possible origins.

Now, an international team of 137 researchers from 64 countries has combined genomic data from all living bat families with evidence from ancient fossils to reconstruct the evolutionary history of the world’s only mammals capable of true powered flight.

The research was conducted through the Bat1K consortium, a global effort to sequence the genomes of all extant bat species. The consortium was co-founded by UCD Professor Emma Teeling.

A new bat family tree

The study examined 103 bat genomes, including 42 newly generated chromosome-level assemblies, covering all 21 recognized bat families. Researchers also incorporated evidence from 44 bat fossils.

Together, these data provide a clearer picture of how bats emerged and spread across the globe.

The findings suggest that bats first evolved in Europe during the late Paleocene. Their descendants later migrated to Africa. As bats became more diverse, separate groups expanded into the Americas, Asia and Australia, giving rise to the major bat lineages found around the world today.

Why are bats so unusual?

Bats are among the most distinctive mammals on Earth. They are the only mammals capable of sustained powered flight, and most species can use sound to navigate and hunt in darkness.

Bats also account for about one-fifth of all living mammals and play important ecological roles around the world.

Many bat species are unusually resistant to disease and can live much longer than other mammals of a similar size. Even so, scientists have spent decades trying to answer fundamental questions about how bats evolved and how their unusual traits developed.

“After decades of research and contradictory findings, it’s amazing that we finally have a robust phylogenetic tree that can be used to properly understand where and how the unique traits of bats evolved,” said Professor Emma Teeling from UCD’s School of Biological and Environmental Sciences. Teeling is a first senior author and co-founder of Bat1K.

“We also have the genomes to reveal the molecular basis of these amazing mammalian adaptations and tell us where bat fossils fall on this tree.”

Associate Professor Graham Hughes and Associate Professor Zisha Huang, both from UCD’s School of Biological and Environmental Sciences, also contributed to the project through the International Bat1K Consortium.

Powered flight and echolocation appeared early

The discovery provides new clues about the origins of two defining bat traits: powered flight and echolocation.

“As bats are the only mammals known to have evolved true powered flight, our findings show that Europe is the most likely place where mammalian powered flight first evolved,” Professor Teeling said.

Researchers also analyzed bat fossils, including Vielasia, which represents the oldest branch of the bat family tree. This fossil evidence suggests that echolocation had already appeared near the beginning of bat evolution.

Taken together, the findings indicate that powered flight and echolocation emerged before modern bat groups began to diversify. These abilities may have contributed to bats’ remarkable evolutionary success.

“The approach we used to model the evolution of fossil and extant species together allows us to do something that would otherwise be impossible: identify the oldest groups of fossil bats while accounting for genomic data, and reveal when and where bats originated,” said lead author Professor Liliana M. Davalos of Stony Brook University.

Reconstructing the ancient bat genome

The researchers also computationally reconstructed the genome of an ancient ancestor shared by all living bats.

This reconstruction offers a glimpse into the genetic makeup of one of the earliest flying mammals and creates a new resource for studying how bats developed their extraordinary diversity.

Scientists can use the dataset to investigate genetic changes associated with flight, echolocation, longevity and disease resistance. It may also help researchers understand why many bats are unusually resistant to disease and live unusually long lives for their size.

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

This genomic resource could eventually contribute to human research into aging, immunity and disease resistance.

“Bats never cease to amaze us. Bats are one of the greatest experiments in evolution,” said Professor Sonja Vernes, a senior author, Bat1K co-founder and director from the University of St Andrews.

“This incredible genomic resource is the culmination of many years of international collaboration on Bat1K, and we are finally able to understand how Bat1K’s amazing biology evolved.”

“This resource for the scientific community allows us to investigate the different types of genomic variation, from single base changes to hundreds or thousands of bases missing in one lineage but present in another, that give rise to the vast variety of bats we share the Earth with and uncover the origins of their unique traits,” added lead author Professor David Ray of Texas Tech University.

Decades of bat samples from around the world

The project is the largest study ever to combine bat genomes and fossils. It draws on samples collected over several decades from bats around the world, including rare species found only in remote areas.

In addition to identifying the likely geographic origins of bats, the analysis resolves some long-standing disagreements about how different bat families are related. The results also revealed unexpected evolutionary connections between groups of rare bats.

“This dataset represents decades of work by field researchers around the world, collecting samples from the most remote locations, from New Zealand to Madagascar,” Professor Teeling said.

“None of this would have been possible without the dedication and collaboration of these researchers, all working together through the Bat1K consortium to collect these samples and tell the evolutionary history of these extraordinary flying mammals.”

The X chromosome helps resolve a long-running controversy

Reconstructing the bat family tree has been particularly difficult because different parts of the bat genome can preserve conflicting signals about its evolutionary history.

One possible explanation is that early bat lineages exchanged genes with one another. As a result, one section of the genome may suggest one set of evolutionary relationships, while another section shows a different pattern.

Researchers discovered that part of the X chromosome preserves a particularly clear record of the underlying relationships between bat groups.

This signal helped the team resolve an evolutionary tree that had been disputed for decades.

This research was supported in part by the European Research Council, Science Foundation Ireland and Research Council Ireland, along with international partners.