[5] H. erectus appeared about 2 million years ago and spread throughout Africa (debatably as another species called Homo ergaster) and Eurasia in several migrations.

[11][12] Separate archaic (non-sapiens) human species including Neanderthals are thought to have survived until around 40,000 years ago.

[16][17][18] Since the early human fossil record began to slowly emerge from the earth, the boundaries and definitions of the genus have been poorly defined and constantly in flux.

Because there was no reason to think it would ever have any additional members, Carl Linnaeus did not even bother to define Homo when he first created it for humans in the 18th century.

Many such names are now regarded as "synonyms" with Homo, including Pithecanthropus,[20] Protanthropus,[21] Sinanthropus,[22] Cyphanthropus,[23] Africanthropus,[24] Telanthropus,[25] Atlanthropus,[26] and Tchadanthropus.

[27][28] Classifying the genus Homo into species and subspecies is subject to incomplete information and remains poorly done.

[29] Some recently extinct species in the genus have been discovered only lately and do not as yet have consensus binomial names (see Denisova hominin).

[31] Wood and Richmond (2000) proposed that Hominini ("hominins") be designated as a tribe that comprised all species of early humans and pre-humans ancestral to humans back to after the chimpanzee–human last common ancestor, and that Hominina be designated a subtribe of Hominini to include only the genus Homo — that is, not including the earlier upright walking hominins of the Pliocene such as Australopithecus, Orrorin tugenensis, Ardipithecus, or Sahelanthropus.

Traditionally, the advent of Homo has been taken to coincide with the first use of stone tools (the Oldowan industry), and thus by definition with the beginning of the Lower Palaeolithic.

[38] LD 350-1, a fossil mandible fragment dated to 2.8 Mya, discovered in 2013 in Afar, Ethiopia, was described as combining "primitive traits seen in early Australopithecus with derived morphology observed in later Homo.

[45] With the publication of Dmanisi skull 5 in 2013, it has become less certain that Asian H. erectus is a descendant of African H. ergaster which was in turn derived from H. habilis.

Instead, H. ergaster and H. erectus appear to be variants of the same species, which may have originated in either Africa or Asia[46] and widely dispersed throughout Eurasia (including Europe, Indonesia, China) by 0.5 Mya.

A 1.5-million-year H. erectus-like lineage appears to have made its way into modern humans through the Denisovans and specifically into the Papuans and aboriginal Australians.

[54] The genomes of non-sub-Saharan African humans show what appear to be numerous independent introgression events involving Neanderthal and in some cases also Denisovans around 45,000 years ago.

[64][63] The genetic structure of some sub-Saharan African groups seems to be indicative of introgression from a west Eurasian population some 3,000 years ago.

[56][66] By about 1.8 million years ago, H. erectus is present in both East Africa (H. ergaster) and in Western Asia (H. georgicus).

[69][70][71] Most notable is the Southern Dispersal of H. sapiens around 60 kya, which led to the lasting peopling of Oceania and Eurasia by anatomically modern humans.

Division of Europeans and East Asians is of the order of 50,000 years, with repeated and significant admixture events throughout Eurasia during the Holocene.

The species status of H. rudolfensis, H. ergaster, H. georgicus, H. antecessor, H. cepranensis, H. rhodesiensis, H. neanderthalensis, Denisova hominin, and H. floresiensis remain under debate.