Genomes and fossils point to Europe as the likely birthplace of bats

The history of bats may have begun in Europe, before their descendants spread around the world. That is the origin favored by a reconstruction published September 23 in Nature, which brought together genomes from 103 species and anatomical information from living and fossil animals. The result comes from combining traces of the past: relationships preserved in DNA, body forms, and the locations of animals that lived long ago. Together, these records allow researchers to investigate where the earliest lineages were and how they acquired their diversity.

Flight helped bats reach distant places, making their present distribution insufficient to locate the group’s origin. They are the only mammals with powered flight and now live on every continent except Antarctica. Their more than 1,500 species include consumers of insects, fruit, nectar, and other foods. Reconstructing this history requires distinguishing later dispersal from the region occupied by the lineage’s earliest members, while also dealing with a sparse fossil record and genetic relationships that are difficult to resolve.

The international team from the Bat1K consortium, in work authored by Ariadna E. Morales and colleagues, began by improving the genetic comparison. A reference genome is an organized assembly of a DNA sequence that serves as a basis for locating and comparing sections across animals. In this study, the assemblies reached the scale of chromosomes, the structures in which DNA is organized. This makes it possible to compare segments within a more continuous framework, rather than relying only on many separate fragments.

The 103 species represented all 21 recognized bat families, and 42 genome assemblies were produced for the work. The researchers used DNA regions considered neutral—less directly shaped by selection for a particular function—to estimate ancestral relationships. The resulting tree, called a phylogeny, indicates which lineages share more recent ancestors. Not every part of the genome tells exactly the same story: rapid splits between lineages, ancient interbreeding, and similarities that evolve independently can generate conflicting signals.

Fossils added references in time and space to the comparison. The anatomical dataset brought together 699 traits across 65 species, including 44 fossil species. Each specimen’s form helps place it on the tree; its age indicates when a lineage already existed; and the place where it was found records a geographic presence. The models combine this information to estimate timing, relationships, and movements, accounting for the fact that lineages arise, disappear, and leave an incomplete record.

When this information was integrated, the reconstruction favored Europe as the region of origin in the late Paleocene, a geological epoch that ended about 56 million years ago. Earlier hypotheses had pointed to North America, Africa, or Asia. The new analysis also shortened the early branches lacking fossil representatives compared with estimates based on molecules alone. Including the preserved specimens therefore changed both the proposed geography and the estimated duration of the earliest stretches of this history.

Another result concerns echolocation: producing sounds and interpreting their echoes to locate obstacles and prey. In the form examined, sounds are generated in the larynx. The fossils’ placement on the tree indicates that this ability preceded the diversification of living families, just as flight was already part of the group’s early history. The analysis still does not determine which of the two abilities appeared first, a question that requires better knowledge of animals close to the lineage’s origin.

The European origin is an inference dependent on the available fossils and the models used to organize them; the transitional animal that would allow researchers to trace the emergence of bats remains unknown. The new tree offers a more consistent framework for investigating this gap and understanding how flight, navigation by echoes, and other traits were distributed among lineages. By bringing together relationships, anatomy, and location, the research connects questions previously examined with more separate pieces of the past.