Bats, belonging to the Order Chiroptera, represent a unique group as the only mammals capable of sustained, powered flight. This singular ability caused centuries of confusion regarding their place on the mammalian family tree. For a long time, their specialized anatomy and incomplete fossil record kept their closest relatives a mystery for biologists. Modern scientific techniques have since clarified this puzzle, revealing surprising evolutionary neighbors.
Why Bats Are Often Misclassified
The distinctive feature of powered flight, shared only with birds and insects, led to many incorrect assumptions about bat ancestry. Their nocturnal habits and winged appearance caused early naturalists to associate them with avian species, despite their clear mammalian traits like fur and live birth. A more common misclassification is the idea that bats are simply “flying mice” or winged rodents.
This belief stems from the small size and fuzzy appearance of many bat species, creating a superficial resemblance to animals in the Order Rodentia. However, the similarities are purely coincidental, representing an example of convergent evolution driven by similar ecological pressures. Bats differ significantly from rodents, including a much longer lifespan for their body size and a reproductive strategy that typically involves only one pup per year, unlike the large, frequent litters characteristic of rodents.
Historically, bats were also grouped with primates, tree shrews, and colugos (flying lemurs) in a superorder called Archonta. This “flying primate” hypothesis suggested that megabats, the large fruit-eating species, were closer to primates than they were to microbats, implying that powered flight may have evolved twice in mammals. Molecular evidence has since definitively rejected this idea, confirming that all bats share a single common ancestor and that these physical resemblances are misleading.
The True Evolutionary Neighbors
Modern genetic analysis has successfully placed bats within the superorder Laurasiatheria, a vast group of placental mammals that originated on the ancient northern supercontinent of Laurasia. This placement contrasts heavily with older, morphology-based classifications and connects bats to a surprising array of animals. The Laurasiatheria superorder includes groups such as Eulipotyphla, which contains shrews, moles, and hedgehogs.
However, the closest living relatives of bats are not shrews, but a collection of mammals that form a clade known as Scrotifera. This clade contains the Order Chiroptera alongside the Carnivora (dogs, cats, bears, seals), Pholidota (pangolins), and the Euungulata (hoofed mammals). Euungulata includes both the Artiodactyla (even-toed ungulates like deer and whales) and the Perissodactyla (odd-toed ungulates like horses and rhinoceroses).
The exact branching pattern within Scrotifera remains a subject of ongoing research, but bats share a more recent common ancestor with the Carnivorans, Pangolins, and Ungulates than they do with the Eulipotyphlans. This means that a cat, a horse, or a pangolin is evolutionarily closer to a bat than a mouse is. The last common ancestor of all Laurasiatherians is estimated to have lived between 76 and 90 million years ago, with the bat lineage diverging from its closest relatives within the Scrotifera clade later on.
How Scientists Confirmed the Kinship
The resolution of the bat’s evolutionary placement was largely achieved by moving beyond the traditional reliance on morphology, using molecular evidence. The frail skeletal structure of bats means their fossil record is notoriously sparse and incomplete, estimated to be missing as much as 61 to 73 percent of their evolutionary history. This lack of clear transitional fossils made it impossible to trace their lineage using physical remains.
The breakthrough came with the advent of large-scale DNA sequencing and phylogenomics, which involve analyzing genetic information from nuclear and mitochondrial genes. By comparing shared gene sequences and retrotransposon data across different mammalian orders, scientists could construct a much more accurate evolutionary tree. This molecular clock approach provided definitive proof that bats belong with the Laurasiatheria grouping.
Molecular studies effectively refuted the historical “flying primate” hypothesis, confirming that the traits shared between megabats and primates were superficial convergences, not signs of common ancestry. By analyzing thousands of base pairs of DNA, researchers were able to pinpoint the shared genetic markers that link bats to the Carnivora and Ungulates, resolving a long-standing problem. This modern methodology has become the standard for clarifying the relationships between highly specialized and morphologically distinct groups.