Smallest ape ever

Simiolus minutus is an extinct species of ape that lived 12.5 million years ago in the Miocene epoch. Based on three fossilized molar teeth measuring approximately 5 millimetres (0.19 inches) across – in particular, an unprecedentedly small M2 molar – it has been extrapolated that this ape could have weighed under 3.5 kilograms (7 pounds 11 ounces), which is about the same as a domestic cat. All of the teeth were unearthed in the Tugen Hills region of central Kenya – the most recent one in 2004 – and are now held at the Kenya National Museum in Nairobi. The findings of the study were published in the December 2018 edition of Journal of Human Evolution on 5 November 2018.

The structure of the teeth indicates that S. minutus predominantly ate leaves, and it’s speculated that this folivorous diet may have proved its downfall. Increasing competition for the same food from a rapidly expanding group of colobine monkeys (a now widespread subfamily of Old World monkeys that includes colobus, langurs, lutungs and proboscis monkeys) was likely a key factor in this ape’s decline.

Until now, the smallest ape on record was Micropithecus clarki, which is estimated to have been of a similar size based on dentition (Fleagle and Simons, 1978; Fleagle, 1988). Excavated in Uganda, M. clarki was a near-contemporary of S. minutus, found in rock dating to the early Miocene.

The smallest extant apes are among the dwarf gibbons (Hylobates), which at the lower end of their range can weigh just under 5 kg (11 lb). The great apes, meanwhile, include today’s largest primates among their number: the eastern lowland gorilla (Gorilla beringei graueri) can reach up to 175 kg (385 lb).

The study was a collaboration between Professor James Rossie of Stony Brook University and the late Professor Andrew Hill of Yale University (both USA).