Homo rudolfensis is an extinct species of archaic human from the Early Pleistocene of East Africa about 2 million years ago (mya).

Early Homo species exhibit marked brain growth compared to Australopithecus predecessors, which is typically explained as a change in diet with a calorie-rich food source, namely meat.

Leakey classified them under the genus Homo because he had reconstructed the skull fragments so that it had a large brain volume and a flat face, but did not assign them to a species.

Because the horizon they were discovered in was, at the time, dated to 2.9–2.6 million years ago (mya), Leakey thought these specimens were a very early human ancestor.

[13] However, the validity of this species has also been debated on material grounds, with some arguing that H. habilis was highly sexually dimorphic like modern non-human apes, with the larger skulls classified as "H. rudolfensis" actually representing male H.

[8][13] In 1999, Wood and biological anthropologist Mark Collard recommended moving rudolfensis and habilis to Australopithecus based on the similarity of dental adaptations.

[16] In 2012, British palaeoanthropologist Meave Leakey described the juvenile partial face KNM-ER 62000 discovered in Koobi Fora, Kenya; noting it shares several similarities to KNM-ER 1470 and is smaller, she assigned it to H. rudolfensis, and, because prepubescent male and female bones should be indistinguishable, differences between juvenile H. rudolfensis and adult H. habilis specimens support species distinction.

Remains from the Shungura Formation, Ethiopia, and Uraha, Malawi, are dated as far back as 2.5–2.4 mya, which would make it the earliest identified species of Homo.

The discovery of LD 350-1, the oldest Homo specimen, dating to 2.8 mya, in the Afar Region of Ethiopia may indicate that the genus evolved from A. afarensis around this time.

[23] Based on 2.1 million year old stone tools from Shangchen, China, possibly an ancestral species to H. rudolfensis and H. habilis dispersed across Asia.

[2] In 1983, American physical anthropologist Ralph Holloway revised the base of the skull and calculated a brain volume of 752–753 cc (45.9–46.0 cu in).

He then said it was possible to predict brain size based on just the face and (disregarding the braincase) calculated 526 cc (32.1 cu in), and chalked up the errors of Leakey's reconstruction to a lack of research of the biological principles of facial anatomy at the time as well as confirmation bias, as a flat-faced reconstruction of the skull aligned with the predominant model of human evolution at the time.

The cheek teeth of KNM-ER 60000, a jawbone, in terms of size are on the lower end for early Homo, except for the third molar which is within range.

Such a wide variation in enamel thickness across the cheek teeth is not exhibited in KNM-ER 1802, which may indicate regional differences among H. rudolfensis populations.

[30] It is generally assumed that pre-H. ergaster hominins, including H. rudolfensis and H. habilis, exhibited sexual dimorphism with males markedly bigger than females.

Nonetheless, the proposed food-gathering models to explain large brain growth necessitate increased daily travel distance.

The mandibular body resists torsion from the bite force or chewing, meaning their jaws could produce unusually powerful stresses while eating.

Nonetheless, the jaw adaptations for processing mechanically challenging food indicates technological advancement did not greatly affect their diet.

[33] Early H. rudolfensis and Paranthropus have exceptionally thick molars for hominins, and the emergence of these two coincides with a cooling and aridity trend in Africa about 2.5 mya.