The 4.2 million-year-old fossil of a tiny monkey that weighed roughly the same as a pineapple has been discovered in Kenya.
Nanopithecus browni was the same size as a modern talapoin monkey, the smallest living Old World monkey species, which weighs only two to three pounds and is about the size of a cottontail rabbit.
Talapoins are part of a large group of monkeys called guenons, which are commonplace across Africa today.
Most species are several times larger in size than Nanopithecus browni.
Guenon evolution is poorly understood but thought to be driven by changes in forest habitats, with the distribution of modern species reflecting the breakup and re-convergence of ancient forests.
A typical guenon monkey compared to how large Nanopithecus browni would have been, and a domestic cat (Carol Ward/PA)
Talapoins live only in West Central Africa, are confined to tropical forests, and are thought to be dwarfed from a larger ancestor in response to life in woody, swampy habitats.
However, the new monkey was found at a site called Kanapoi, in Kenya, on the eastern side of the continent.
The habitat was dry and covered with grasslands and open forests – a very different place from the tropical forests of Cameroon and Gabon in West Central Africa.
Kanapoi is also where remains of some of the earliest human ancestors, Australopithecus anamensis, have been found.
Nanopithecus browni is the second oldest guenon found so far, just younger than the guenon single tooth found 10 years ago on the Arabian Peninsula, scientists say.
According to researchers, the newly discovered member of the primate family reveals that dwarfing occurred far longer ago than scientists suspected and may have happened more than once, and in very different habitats perhaps for different reasons.
Fredrick Kyalo Manthi, of the National Museums of Kenya, said: “The discovery of Nanopithecus browni reaffirms Kenya’s contribution to understanding the evolution and diversity of Pliocene fauna and the environmental contexts in which they lived.
“Environmental changes during the Plio-Pleistocene may have influenced the present-day distribution of guenons.”
The discovery was made by researchers from the National Museums of Kenya, University of Arkansas, University of Missouri and Duke University, and published in the Journal of Human Evolution.