By Maina Kiarie
Orrorin Tugenensis is considered the second-oldest (after Sahelanthropus) known hominin ancestor that is likely related to modern humans. The species lived between 6.2 and 5.8 million years ago and is the only species classified in the Orrorin genus.
Orrorin was discovered in 2000 by a team led by French paleontologist Brigitte Senut and French geologist Martin Pickford in the Tugen Hills of Central Rift Valley. Orrorin Tugenensis in Tugen means “original man in the Tugen region.” Individuals of this species were approximately the size of a chimpanzee and had ape-like features although they were bipedal (walked on two legs). They had small teeth with thick enamels which are similar to modern humans. Orrorin climbed trees and also walked upright with two legs on the ground.
In the Museums collection are 13 fossils from at least 5 Orrorin individuals and scientists estimate that it was about 1.5 times larger than Australopithecus Afarensis. That would place it about the size of a female chimpanzee at between 30 and 50 kg.
The species is nicknamed Millennium Man and from their low, rounded molars and small canine teeth, it can be inferred that they ate a mainly plant-based diet including leaves, fruit, seeds, roots, nuts as well as insects.
There is still a lot more to be learned about Orrorin such as whether it is a direct human ancestor to Homo sapiens and how that affects the Australopithecus Afarensis branch. Also yet to be answered is the relationship of Orrorin to Sahelantropus tchadensis.