Our pre-human ancestors mastered the task of leaping through the trees like high-flying acrobats, according to a study of a 52-million- year-old ankle fossil.
For years, scientists thought the ancestors of today's humans, monkeys, lemurs and apes were relatively slow and deliberate animals, using their grasping hands and feet to creep along small twigs and branches to stalk insects or find flowers and fruits.
Researchers from Duke University in the US studied scans of Donrussellia's ankle - a quarter-inch-long bone in the lower part of the ankle joint found in France - and compared it to other animals, using computer algorithms to analyse the 3D digital shape of each tiny bone.
Previously only known from jaws and teeth, Donrussellia is thought be one of the earliest members of the primate family tree, on the branch leading to lemurs, lorises and bush babies, researchers said.
They found that Donrussellia's ankle was not like those of other primates, but was more similar to those of treeshrews and other non primate species.
The team's analyses also suggest the animal did not just clamber or scurry along small branches. Instead, it may have been able to bound between trunks and branches, using its grasping feet to stick the landing.
Contrary to what many scientists thought - the first primates may have evolved their acrobatic leaping skills first, while anatomical changes that allowed them to cling to slender branch tips and creep from tree to tree came later, researchers said.
"Being able to jump from one tree to another might have been important, especially if there were ground predators around waiting to snag them," said Doug Boyer, assistant professor at Duke University.
The study was published in the Journal of Human Evolution.
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