Joint analysis of 103 bat genomes and 44 fossils places bat origins in Europe

A 103-species set is thin against more than 1,500 living bat species, about 6.9 percent of them ^[9]. The coverage that counts here sits at a different level: the collection includes representatives of every one of the 21 currently recognised bat families ^[6]. Every deep branch of the tree therefore has a sequenced genome on it, which is what a dating analysis needs. Variation within a family is sampled far more sparsely, and that is not the question this dataset was built to answer.

The geography leans on the fossils. The team modelled 44 fossil bats from around the world together with the living species in a single analysis ^[7]. Liliana M. Davalos of Stony Brook University, a senior author, said the approach "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" ^[11]. A root placed this way depends on where fossil bats have been dug up, and the phys.org report does not give the uncertainty on the 65-million-year estimate. Samples behind the genomes were collected over decades, including from the rarest and most unusual bat families in remote locations ^[17].

Vielasia falls within the oldest branch of the revised tree, which puts echolocation before the diversification of modern bats ^[13]. The authors take that to mean echolocation and powered flight were both established near the origin of the group ^[14]. Bats are the only mammals capable of true powered flight, and most of them orient and hunt in darkness using sound alone ^[18], so a tree that separates those two traits in time would have implied a long stretch of flying, non-echolocating bats. On this tree they arrive together.

"Bats constantly surprise us. They are one of evolution's greatest experiments," said Sonja Vernes of the University of St Andrews, senior author and director of Bat1K ^[12].

Many bat species resist disease well and live exceptionally long lives for their size ^[15], and the study's own framing is that the genomic resource provides the first robust evolutionary framework for investigating the genes behind those traits, with possible relevance to human research on aging and immunity ^[16]. The framework is where the paper stops. Identifying a gene, showing it changes lifespan, and showing the same pathway operates in a mammal that does not fly are three separate pieces of work, none of them in this paper. The dataset does change the control: a comparison that finds an unusual immune gene in one bat species can now be checked against 20 other families before anyone calls it a bat adaptation ^[6].

The team also revised the bat evolutionary tree using new methods, settling several long-running arguments about how the major groups relate to one another ^[10].