Kenyanthropus is a genus of extinct hominin identified from the Lomekwi site by Lake Turkana, Kenya, dated to 3.3 to 3.2 million years ago during the Middle Pliocene.

Before its naming in 2001, Australopithecus afarensis was widely regarded as the only australopithecine to exist during the Middle Pliocene, but Kenyanthropus evinces a greater diversity than once acknowledged.

Kenyanthropus is most recognisable by an unusually flat face and small teeth for such an early hominin, with values on the extremes or beyond the range of variation for australopithecines in regard to these features.

The Lomekwi site also yielded the earliest stone tool industry, the Lomekwian, characterised by the rudimentary production of simple flakes by pounding a core against an anvil or with a hammerstone.

In August 1998, field technician Blasto Onyango discovered a hominin partial left maxilla (upper jaw), specimen KNM-WT 38350, on the Kenyan Lomekwi dig site by Lake Turkana, overseen by prominent paleoanthropologists Louise and Meave Leakey.

In August 1999 at the Lomekwi site, research assistant Justus Erus discovered an uncharacteristically flat-faced australopithecine skull, specimen KNM-WT 40000.

The 20th century generated an overabundance of hominin genera plunging the field into taxonomic turmoil, until German evolutionary biologist Ernst Mayr, surveying a "bewildering diversity of names", decided to recognise only a single genus, Homo, containing a few species.

In addition to Kenyanthropus, the 1990s saw the introduction of A. bahrelghazali, Ardipithecus, Orrorin, and Sahelanthropus, which has complicated discussions of hominin diversity,[3] though the latter three have not been met with much resistance on account of their greater age (all predating Australopithecus).

[4] Meave Leakey and colleagues drew attention to namely the flat face and small cheek teeth, in addition to several other traits, to distinguish the genus from earlier Ardipithecus, contemporary and later Australopithecus, and later Paranthropus.

[1] Leakey and colleagues further drew parallels with KNM-WT 40000 and the 2 million year old KNM-ER 1470 assigned to Homo rudolfensis, attributing differences in braincase and nasal anatomy to archaicness.

[1] In 2003, American palaeoanthropologist Tim D. White was concerned that KNM-WT 40000 was far too distorted to obtain any accurate metrics for classification purposes, especially because the skull was splintered into over 1,100 pieces often measuring less than 1 cm (0.39 in) across.

[6] In 2003, Spanish writer Camilo José Cela Conde and evolutionary biologist Francisco J. Ayala proposed resurrecting the genus "Praeanthropus" to house all australopithecines which are not Ardipithecus, Paranthropus, or A. africanus, though they opted to synonymise Kenyanthropus with Homo as "H.

The clivus inclines at 45° (there is relaxed sub-nasal prognathism), steeper than almost all other australopithecine specimens (on the upper end of variation for Paranthropus), more comparable to H. rudolfensis and H. habilis.

Unlike A. afarensis, Kenyanthropus lacks the anterior pillars, bony columns running down from the nasal aperture (nose hole).

Much later Paranthropus are also characterised by relatively flat faces, but this is generally considered to be an adaptation to maximise bite force through enormous teeth, which Kenyanthropus enigmatically does not have.

[8] The tools are attributed to Kenyanthropus as it is the only hominin identified at the site, but in 2015, anthropologist Fred Spoor suggested that at least some of the indeterminate specimens may be assignable to A. deyiremeda as the two species have somewhat similar maxillary anatomy.

[13][14] Similarly, the bovid remains at Lomekwi are suggestive of a wet mosaic environment featuring both grasslands and forests on a lakeside or floodplain.

Theropithecus brumpti is the most common monkey at the site as well as the rest of the Turkana Basin at this time; this species tends to live in more forested and closed environments.

At the fossiliferous A. afarensis Hadar site in Ethiopia, Theropithecus darti is the most common monkey, which tends to prefer drier conditions conducive to wood- or grassland environments.

[1] Kenyanthropus, A. afarensis, and A. deyiremeda all coexisted in the same time and region, and, because their anatomy largely diverges in areas relevant to chewing, they may have practised niche partitioning and foraged for different food items.