A landmark study, the largest combined bat genome and fossil study ever undertaken, finds that bats most likely originated in Europe around 65 million years ago, before spreading across the world.

The work also reveals that echolocation, like flight, evolved near the dawn of bat evolution, and lays the groundwork for research into the genetic basis of bats' exceptional longevity and disease resistance, with potential relevance to human health.

• Largest bat genome and fossil study ever conducted (103 genomes, 44 fossils), generated and analysed by 137 researchers from 64 countries
• Bats most likely arose in Europe around 65 million years ago, not Asia, Africa or North America as long assumed
• Echolocation and flight evolved early in bats
• The bat family tree has been redrawn, resolving debates that have puzzled scientists for decades
• First-ever reconstruction of the genome of the ancestor of all living bats
• New foundation for research into bat disease resistance and long lifespans, with potential relevance to human ageing and disease research

Published in Nature, an international team of 137 researchers from 64 countries, working together as part of the Bat1K consortium, combined genomic and fossil evidence to show that bats, and thus mammalian flight, most likely originated in Europe around 65 million years ago.

International collaborative project

Co-author of the study, Dr Emma Stone from the Bat Conservation Research Lab in the University of Bath’s Centre for Evolution in the Department of Life Sciences, said:

This was a huge collaborative study, proving that global collaboration in science can break new ground, working across the globe over 137 researchers came together to contribute to new understanding of when and where bats originated.

It was a privilege to be able to contribute in a small way from my long term research programme studying African bats.”

These results overturned previous hypotheses proposing Asian, African or North American origins. Their earliest descendants then dispersed into Africa, establishing a Europe-Africa hub from which bats then expanded into Asia, the Americas and Australia.

The team assembled the largest collection of high-quality bat genomes to date, covering 103 species and representing every one of the currently recognised 21 bat families.

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

They combined them with 44 fossil bats from across the globe to reconstruct the evolutionary history of the world's only flying mammals.

Bats are among the most extraordinary mammals on Earth. They are the only mammals capable of true powered flight. Most bats orient and hunt in complete darkness using sound alone. With more than 1,500 species distributed across the globe, bats account for one fifth of all living mammals and play vital roles in maintaining healthy ecosystems by pollinating plants, dispersing seeds and consuming vast numbers of insect pests.

“Bats constantly surprise us. They are one of evolution’s greatest experiments. This extraordinary genomic resource, the culmination of years of international cooperation of Bat1K, is finally allowing us to understand how their remarkable biology evolved,” says Professor Sonja Vernes, University of St Andrews, Bat1K Co-founding Director and senior author.

Furthermore, many bat species show remarkable resistance to disease and live exceptionally long lives for their size. The genomic resource built for this study gives scientists the first robust evolutionary framework to investigate the genes behind these traits. This work could eventually inform human research into ageing, immunity and disease resistance.

Yet despite their extraordinary biology and ecological importance, scientists have struggled for decades to answer some of the most fundamental questions about bat evolution. Where did bats come from? How are the bat families related? When did flight and echolocation emerge? And how did bats evolve the unusual traits that set them apart from other mammals?

This study provides answers to many of these long-standing questions. The team analysed these genomes and fossils using novel methods and revised the bat evolutionary tree, resolving several long-running debates about how the major bat groups are related.

“It is extraordinary, after decades of research and conflicting findings, we finally have a robust phylogenetic tree that we can now use to properly understand how bats’ unique traits evolved.

“We also have the genomes to uncover the molecular basis of these spectacular adaptations and know where the fossil bats fall in this tree,” says Professor Emma Teeling, University College Dublin, Co-founding Director of Bat1K and senior author.

From bumblebee to sucker-footed bats

This work represents the largest combined bat genome and fossil study ever undertaken. Building this dataset required samples collected over decades from bats across the world, including representatives of some of the rarest and most unusual bat families, found in the most remote locations.

Among them are the tiny bumblebee bats of Thailand and Myanmar, widely considered the Earth’s smallest mammal, the remarkable sucker-footed bats of Madagascar, which have suction cups on their wrists and ankles that they use to cling to smooth leaves, and one of New Zealand’s only native mammals, the lesser short-tailed bat, which “walks” along the forest floor using its folded wings as forelegs.

Flight and echolocation evolved early in bats

The fossil evidence also provides important clues about another long-standing mystery: when bats first evolved echolocation.

The placement of the fossil bat Vielasia within the oldest branch of the bat family tree indicates that echolocation predates the diversification of modern bats. The finding suggests that two of the defining characteristics of bat biology, echolocation and powered flight, were established near the origin of the group itself, helping explain the extraordinary evolutionary success of bats over the subsequent 65 million years.

The team also reconstructed the genome of the bat ancestor, showing what the first genome of a mammal capable of flight would have looked like.

“This resource for the community of scientists allows them to investigate the different types of genomic variation, from single base changes to hundreds or thousands of bases missing from one lineage but present in another, that have given rise to the huge variety of bats that we share the planet with, and the origins of their unique characteristics,” says Professor David Ray, Texas Tech University, senior author.

This now gives scientists a genomic map for how one lineage of mammals evolved powered flight, advanced biosonar, exceptional longevity and unusual disease resistance, a foundation to trace the genetic basis of these traits with relevance well beyond bats.