Botched ID discovery prompts lemur rethink

Ancient dental records offer a radical new explanation for how Madagascar’s lemurs evolved.

Scientists have long believed that the island’s diverse primates arose following a single colonisation event from mainland Africa between 50 and 40 million years ago.

Now, an alternative explanation published in the journal Nature Communications reveals a case of mistaken identity that has remained hidden for half a century.

Jaw fragments unearthed in Kenya in the 1960s were initially described by American palaeontologist George Gaylord Simpson as belonging to a new species of primate. But another scientist, Alan Walker, persuaded Simpson that the freshly named Propotto leakyi was actually a type of fruit bat.

Recently, a team of researchers led by the late Gregg Gunnell of Duke University in the US re-examined the Propotto fossils and constructed new phylogenetic trees — charts which show how groups of species are related to one another.

Their analysis shows that Propotto was indeed a primate, and is a predecessor of Madagascar’s aye-aye (Daubentonia madagascariensis), a species of lemur and the world’s largest nocturnal primate.

Together with other primate remains recovered in Egypt, the discovery places the last common ancestor of the aye-aye on the African continent around 28 million years ago.

The evidence suggests that Madagascar’s lemurs evolved from two distinct primate lineages, challenging the long-held view of a single dispersal and colonisation event.

Gunnell and colleagues also characterise the timing of lemur dispersal to Madagascar as happening much later than previously thought: as recently as 20 million years ago.

The authors acknowledge that this profound restructuring of the lemur family tree depends entirely on dental evidence, and that “more rigorous tests of these hypotheses will only be possible as new and more complete fossils are discovered”.