Elephants are closer kin to golden moles than to rhinos or hippos
Elephants, manatees, aardvarks, hyraxes and tiny golden moles look nothing alike, yet they share one family tree. Nobody recognised it until DNA studies in 1998. The group, Afrotheria, grew up on Africa when it was an island continent, and its members evolved into lookalikes of mammals elsewhere.
Water isolated Africa from the Cretaceous onward, and only in the early Miocene, around 20 million years ago, did the Afro-Arabian landmass crash into Eurasia. Rodents, rabbits, carnivores and hoofed animals from the northern continents could not reach it for much of that time, so afrotheres filled their roles through convergent evolution. Sengis, tenrecs and golden moles became the insect-eaters, hyraxes stood in for rodents and rabbits, the aardvark took the ant-eater's job, and elephants and their relatives played the large grazers and browsers. Sea cows went aquatic and spread around the world by sea.
Before genetics, anatomists scattered these animals across unrelated groups. Hyraxes, elephants and sea cows were tied to horses and rhinos, the small insect-eaters were lumped into a catch-all category now known to be invalid, and the aardvark was paired with pangolins and armadillos. A few studies going back to the 1920s had hinted at links, and the trio of elephants, sea cows and hyraxes was long accepted as a unit. Molecular data finally revealed the full group. Anatomical clues now back it up: many members have lots of vertebrae, similar ankle bones, late-arriving adult teeth, testes that stay inside the body near the kidneys, and often a long, mobile snout.
Genome-scale studies suggest afrotheres and another old lineage, the xenarthrans, sit side by side at the base of the placental mammal tree, pointing to an ancient Gondwanan branch. A Paleocene African fossil, Ocepeia, offers a glimpse of what the ancestor may have looked like.
The group was once far more widespread. Before the Quaternary extinctions, elephant relatives lived on every continent except Australia and Antarctica, and hyraxes roamed much of Eurasia until the end of the Pliocene. Today many members face high extinction risk. Afrotheria accounts for nearly a third of the mammal orders in Africa and Madagascar but only 75 of their more than 1,200 mammal species, so each loss cuts deep.
Source: Afrotheria
