Convergence or Introgression?

I.d-5.) Pthirus gorillae and Pthirus pubis

The human pubic louse Pthirus pubis diverged from the gorilla louse Pthirus gorillae around 3 MYA.

I.e. Benefits of Hybridization

I.e-1.) Examples from the Cercopithecoids

(Ackermann et al., 2006)

I.f. The Importance of Correlating Genetic Events with Fossil Record Events

Regardless of whether apparently recent divergence times for certain genes result from introgression or intraspecific variation, determining which genetic changes correlate with certain anatomical changes can help us to better understand the functions of the genes in question.

II. Overview of the Hominoid Fossil Record

II.a. Oligocene (35 to 33 MYA)

[24-27 MYA] Proconsul hamiltoni

II.b. Miocene [23.03 to 5.333 MYA]

Original divergence of the human, chimpanzee, and gorilla lineages, about 13 MYA.

(Begun, 2010)

II.b-1.) Antiquanian [23.03 — 20.04 MYA]

II.b-2.) Burdigalian [20.04 — 15.97 MYA]

II.b-3.) Langhian [15.97 — 13.82 MYA]

II.b-4.) Serravallian [13.82 — 11.63 MYA]

II.b-5.) Tortonian [11.63 — 7.246 MYA]

II.b-6.) Messinian [7.246 — 5.333 MYA]

II.c. Pliocene [5.333 million to 2.58 MYA]

Interbreeding between the human and chimpanzee lineages ends possibly as recently as 4 MYA.

(Haile-Selassie et al., 2017)

II.c-1.) Zanclean [5.333 — 3.6 MYA]

II.c-2.) Piacenzian [3.6 — 2.58 MYA]

II.d. Pleistocene

2,588,000 to 11,700 years ago.

II.d-1.) Gelasian [2.58 — 1.8 MYA]

II.d-2.) Calabrian [1.8 MYA — 781 KYA]

II.d-3.) Ionian [781 KYA — 126 KYA]

II.d-4.) Tarantian [126 KYA — 11.7 KYA]

II.d. Holocene

III. Anatomical Curiosities, Anachronisms, and Fringe Theories

III.a. The Enigmatic Australopithecines

III.a-1.) Allometric Inconsistencies

Australopithecus anamensis

Australopithecus afarensis

Type specimen AL 288-1 or “Lucy” (Johanson, 1976) had a humerofemoral index of 85.1, “intermediate” when compared with Homo sapiens and the other Great Apes. (Jungers, 1982)

A study of the limb proportions of the Australopithecine

“In contrast, A. afarensis and anamensis more closely approximate a human pattern of forelimb to hindlimb joint size. This is an unanticipated complication in our understanding of early human evolution. In general, craniodental morphology tracks time in species of Australopithecus: A. anamensis (3.5-4.1 Ma) is the most primitive with a strongly sloping symphysis, large canine roots, etc., A. afarensis (3.0-3.6 Ma) is less primitive (Berger & McHenry, 1998)

Australopithecus africanus

“New discoveries of A. africanus fossils from Member 4 Sterkfontein reveal a body form quite unlike earlier Australopithecus species. The new adult material consists of over 48 fore- and hindlimb specimens and includes an associated partial skeleton, Stw 431. The forelimbs are relatively large: the average size of their joints corresponds to a modern human with body mass of 53 kg. The hindlimbs are much smaller with an average size matching a modern human of only 33 kg. Analyses of the Stw 431 partial skeleton confirm these results.” (Berger & McHenry, 1998)

“A. africanus (2.6-3.0 Ma) shares many derived characteristics with early Homo (e.g., expanded brain, reduced canine, bicuspid lower third premolar, reduced prognathism, greater flexion of the cranial base, deeper TMJ). The new postcranial material, however, reveals an apparently primitive morphology of relatively large forelimb and small hindlimb joints resembling more the pongid than the human pattern. More pongid-like proportions are also present in the two known associated partial skeletons of H. habilis (OH 62 and KNM-ER 3735). This may imply either (1) that A. africanus and H. habilis evolved craniodental characters in parallel with the lineage leading to later Homo, or (2) that fore- to hindlimb proportions of A. afarensis (and perhaps A. anamensis) evolved independent of the lineage leading to Homo and does not imply a close phylogenetic link with Homo.” (Berger & McHenry, 1998)

Australopithecus habilis (Homo habilis)

OH 62 – Homo habilis?

“Although the difference in humerofemoral proportions between OH 62 and AL 288-1 does not exceed variation in the extant samples, it is rare. When humerofemoral midshaft circumferences are compared, the difference between OH 62 and AL 288-1 is fairly common in extant species. This, in combination with error associated with the limb lengths estimates, suggests that it may be premature to consider H. (or Australopithecus) habilis as having more apelike limb proportions than those in A. afarensis.”
J Hum Evol. 2002 Oct;43(4):529-48.
Early hominin limb proportions.
Richmond BG1, Aiello LC, Wood BA.
(Richmond et al., 2002)

“The humerus and femur of the fossil hominid OH 62 are badly damaged and their lengths are not directly measurable (Johanson et al., 1987). Nevertheless, using relatively intact reference materials from another early hominid, AL 288-1, Johanson et al. (1987) reconstructed the bones to estimate the humerofemoral index, which falls well above the range for modern Homo, above the estimate for AL 288-1, and within the range for Pan paniscus. The reconstruction of missing bone by the method originally employed for OH 62 is broadly reproducible in a representative modern sample of Homo, making possible the estimation of an associated error term intrinsic to this method. Using the approximate variance of the ratio mean (Kish, 1965), shown here to be a good estimator of the sample variance of the humerofemoral index, the analysis of this modern sample extrapolated to other living hominoids gives quite acceptable results. Applied to OH 62, it suggests an error term associated with the estimated humerofemoral index so substantial that it is only possible to situate the index somewhere between the distributions for Homo and Gorilla, and quite possibly not above the index for AL 288-1. On the other hand, the predicted distribution for the humerofemoral index of AL 288-1 is more securely placed between the distributions for Homo and Pan paniscus.”
Am J Phys Anthropol. 1990 Sep;83(1):25-33.
Deconstructing reconstruction: the OH 62 humerofemoral index.
Korey KA1.
(Korey, 1990)

Bouri skeleton, BOU-VP 12/1

“The humerofemoral index of BOU-VP 12/1 differs significantly from both OH 62 and AL 288-1, but not from KNM-WT 15000. Published length estimates, if correct, suggest that the relative forearm length of BOU-VP 12/1 is unique among hominins, exceeding those of the African apes and resembling the proportions in Pongo.”
J Hum Evol. 2002 Oct;43(4):529-48.
Early hominin limb proportions.
Richmond BG1, Aiello LC, Wood BA.
(Richmond et al., 2002)

According to Green et al., Homo habilis may have had either apelike or humanlike limb proportions (2007), or, as is more likely the case, displayed a range that was similar to H. sapiens and Pr./Au. afarensis on the one end and similar to Au. africanus on the other.

OH 34 – H. erectus or Par. boisei?

(Green et al., 2007)(Berger, 1998)

Australopithecus garhi

Homo habilis, which some researchers, including Richard Leakey, have suggested would be better reclassified as Australopithecus habilis.

III.a-2.) Digitigrade Ancestry of Præanthropus

In a letter to Nature, entitled Evidence that humans evolved from a knuckle-walking ancestor, Brian G. Richmond and David S. Strait of George Washington University argue that analysis of the carpal morphology of Pr./Au. anamensis (KNM-ER 20419) and Pr./Au. afarensius (AL 288-1) demonstrate retained specializations associated with knuckle-walking, indicating a digitigrade quadruped ancestor for Præanthropus. (Richmond & Strait, 2000)

Retained from what? This is interesting because Ardipithecus, which lived closer to the date of divergence for Hominina and Panina, was not a knuckle-walker. Ardipithecus was most likely an arboreally plantigrade quadruped and a terrestrial plantigrade biped, making it unlikely to have been ancestral to a terrestrially digitigrade quadruped (like modern chimpanzees) that later spawned arboreally suspensory, terrestrial plantigrade bipeds (like the Australopiths). How and why evidence of knuckle-walking adaptations would have been retained in terrestrial bipeds who descended from terrestrial bipeds lacking such adaptations is currently somewhat of a mystery, to which molecular evidence of an interbreeding event between the ancestors of Panina and the ancestors of Hominina as late as 4 MYA provides a valuable clue.

III.a-3.) Gorilla-like Traits in Paranthropus

III.b. Ancestral Bipedalism

Also known as “Ancestral Bipedalism”,

The main consequence of this hypothesis is the placement of A. afarensis in a position ancestral to African apes. An argument in support of this alternative paradigm is formulated concerning the evolution of knuckle-walking in African apes from ancestors whose bipedalism was already well developed. Published data are cited, particularly concerning the structure of the wrist, which accommodate poorly the evolution of African apes from palmigrad-walking or brachiating ancestors resembling Proconsul africanus or Pongo. These arguments suggest that an alternative paradigm of hominoid evolution placing A. afarensis ancestral to Homo, Gorilla, and Pan warrants further consideration.

(Edelstein, 1987)

S. J. Edelstein, An Alternative Paradigm for Hominoid Evolution. HUMAN EVOLUTION Vol. 2 - N. 2 (169-174) - 1987
<http://www.unige.ch/sciences/biochimie/Edelstein/Edelstein%201987%20Alternative%20paradigm.pdf>

An alternate version of this model would make genus Australopithecus (in its most inclusive sense, roughly corresponding to subtribe Australopithecina, including both Praeanthropus and Paranthropus) ancestral to Homo, Pan, and Gorilla, whith the gracile Australopithecines (genus Australopithecus in its more commonly understood sense) ancestral to Homo and Pan, and the robust Australopithecines (sometimes separated into their own genus, Paranthropus) ancestral to genus Gorilla, based on numberous morphological similarities otherwise interpreted as homoplasy (convergent or parallel evolution).

III.b-1.) Australopithecus as an Ancestor of Panina

One of the main problems with this involves the earliest gracile Australopithecines showing evidence in their carpals of characteristics retained from a knuckle-walking ancestor. This would mean that chimpanzees evolved digitigrade quadrupedality independently of the gorilla lineage from a non-knuckle-walking biped (Australopithecus) who in turn evolved from an unrepresented digitigrade ancestor, who in turn evolved from a non-knuckle-walking bipedal ancestor (Ardipithecus).

III.b-2.) Paranthropus as an Ancestor of Gorilla

III.b-3.) Incompatibilities with the Genetic Clock

III.b-4.) Earlier Examples of Bipedality

III.c. Regressive similarity to Oreopithecus

III.c-1.) Oreopithecus & the Australopiths

III.c-2.) The Hallux of Oreopithecus & Ardipithecus

III.c-3.) Sahelanthropus, Orrorin & the Australopiths

III.c-4.) Island populations and the Aquatic Ape Theory

Species can’t diverge without being isolated. https://www.youtube.com/watch?v=1gjUXT99gC0 Is Evolution Predictable?

(Niemtiz, 2010)

III.c-5.) Ancestral Bipedalism Revisited

IV. The Interbreeding Model

First it is important to distinguish between an interbreeding model and a hybridization model. While use of the term “hybridization” implies that introgressions occurred subsequent to divergence into (mostly) genetically isolated lineages representing separate, distinct species, an interbreeding model of hominid evolution merely requires what Wakely refers to as “less extreme versions of divergence with gene flow” (2008) which could be thought to include geneflow through intraspecific hybrid populations – in other words, that genetic isolation occurred gradually over a long period of time. So while an interbreeding model of hominid evolution potentially subsumes any and all interspecific hybridization hypotheses, it does not definitively include them, giving no preference to post-speciation introgressions (interspecific hybridization with backcrossing) over gradual divergence with localized intraspecific hybridization events and extensive “intragression”, and therefore allows for the possibility that the individuals who interbred existed as part of a more diverse species comprising a continuum of interfertility.

IV.a. Possible Anatomical Corroborations

Within the framework of the interbreeding model, we can revisit the anatomical curiosities borne out in the fossil record in a new context.

IV.a-1.) Knuckle-walking as Evidence of Introgression

About 4.2 MYA genus Præanthropus appears, bearing, as noted earlier, carpal evidence of retained knuckle-walking adaptations absent in their probable immediate ancestor, Ardipithecus. This coincides with low-end estimates for an interbreeding event between the ancestors of humans and chimpanzees roughly 7-4 MYA, approximately one million years after their initial divergence from a common ancestor 8-5 MYA according to older estimates using the genetic clock, but more recent estimates for the last divergence from a common ancestor around 5.4 MYA would antedate the earliest evidence for Præanthropus in the fossil record by about 1.2 MY.

The appearance of retained knuckle-walking adaptations in Præanthropus is problematic if the Australopiths descended from an Ardipithecus-like bipedal ancestor that did not use its knuckles to support itself when moving quadrupedally, which had diverged allopatrically from branches of the hominid family tree which eventually produced knuckle-walkers. This speaks strongly in favor of the evidence for retained knuckle-walking adaptations in Præanthropus indicating descent from a time when genetic isolation of modern lineages was still incomplete, with a hybridization event between Hominina and Panina (or the immediate ancestors thereof) subsequent both to their initial divergence from the first hominin concestor 10 MYA and to the adoption of a knuckle-walking mode of locomotion by at least some ancestors in the lineage leading to the extant subtribe Panina prior to their last divergence as late as 4 MYA.

Whether the appearance of knuckle-walking both in tribe Gorillini and in subtribe Panina of tribe Hominini, while the hominin concestor (and logically therefore the hominine concestor) is unlikely to have been a knuckle-walker, is the result of convergent evolution (“linear” homoplasy) or an example of introgressions from tribe Gorillini into Hominini (“horizontal” homoplasy) is unclear, however, “[i]n 30% of the genome, gorilla is closer to human or chimpanzee than the latter are to each other,” (Scally & Dutheil et al., 2012), meaning that chimpanzees have genetic material in common with gorillas which humans do not possess. While Scally & Dutheil et al. attribute this to separate selection forces in the human and chimpanzee lineages, considering the genetic differences between even extant populations of humans, chimpanzees, and gorillas are more minute than sometimes found between members of the same species (Diamond, 1991), introgression cannot be ruled out as an explanation.

Thus, it’s probable that Præanthropus displays evidence of retained knuckle-walking adaptations in its carpals due to introgression from the chimpanzee lineage, which had in turn acquired its digitigrade form of quadrupedality via introgression from the gorilla lineage, or else Præanthropus and the chimpanzee lineage both experienced introgression through (an) unattested Hominini-Gorillini hybrid population(s), or some combination thereof. It may be that the chimpanzee lineage is the hybrid population that Præanthropus experienced backcrossing from, or that the human lineage is unattested from this time period and that both Præanthropus and the chimpanzee lineage are hybrid populations. (For more discussion on this, see Identifying Hybrid Populations.)

IV.a-2.) Effects among the Australopithecines

Concerning the aforementioned inconsistencies in Australopithecine limb allometry,

“When applied to the fossil samples, upper:lower limb-size proportions in A. afarensis are similar to those of humans (p = 0.878) and are significantly different from all great ape proportions (p = 0.034), while Australopithecus africanus is more similar to the apes (p = 0.180) and significantly different from humans and A. afarensis (p = 0.031). These results strongly support the hypothesis that A. africanus possessed more apelike limb-size proportions than A. afarensis, suggesting that A. africanus either evolved from a more postcranially primitive ancestor than A. afarensis or that the more apelike limb-size proportions of A. africanus were secondarily derived from an A. afarensis-like ancestor.” (Green et al. 2007, Abstract)

Given the evidence for interbreeding events between the human and chimpanzee lineages as recently as 4 MYA, shortly after the appearance in the fossil record of Au./Pr. anamensis, it is entirely possible that A. africanus did not simplistically “evolve from” a postcranially more primitive ancestor but that its “primitive” limb proportions, rather than being secondarily derived, were inherited from a postcranially A. afarensis-like ancestor that experienced introgression from the chimpanzee lineage via backcrossing from a hybrid population facilitating gene flow.

IV.b. Identifying Hybrid Populations

IV.b-1.) Genus Præanthropus

IV.b-2.) Genus Australopithecus

IV.b-3.) Genus Paranthropus

IV.b-4.) Genus Pan

IV.c.) Introgressions

IV.c-1.) First Introgression Period

IV.c-1.) Second Introgression Period

IV.c-2A.) Occidental Introgression

IV.c-2B.) Oriental Introgression

IV.c-3.) Third Introgression

IV.c-3.) Third Introgression

IV.c-3B.) Third Introgression Period

IV.c-3A.) Third Introgression Period: Phase I

V. Conclusions

Of the genus Homo, genus Pan, genus Gorilla, Scally & Dutheil et al. write “[i]t is notable that species within at least three of these genera continued to exchange genetic material long after separation.” (2012) Thus, the expectation of single-point concestors, with each lineage diverging instantaneously and irrevocably into fully-isolated lineages, is wishful thinking borne of a desire for taxonomic convenience.

V.a. Implications on Hominoid Taxonomy

V.a-1. Reorganization of the Family Tree for “Splitters”

Superfamily Hominoidea

Family Proconsulidae

Hominoid concestor (human-gibbon MRCA) –

Family Hylobatidae

Family Hominidae

Subfamily Kenyapithecinae – simultaneously the palæosubfamily to both Homininae and Ponginae, comprising organisms that existed at a time before the ancestors of the extant forms of Homininae and Ponginae could have justifiably been separable into distinct subfamilies.

Tribe Kenyapithecini –

The geographical distribution of this group was pan-Eurafrican, existing both north and south of what is now the Mediterranean Sea, with the subfamily's namesake genus, Kenyapithecus, likely being one of the southernmost examples.

Hominid concestor (human-orangutan MRCA) –

Subtribe Græcopithecina (my classification)–

Genus Ouranopithecus –

Species Ouranopithecus macedoniensis –

Genus Pierolapithecus

Species Pierolapithecus catalaunicus –

Genus Græcopithecus

Species Græcopithecus freybergi –

Subtribe Kenyapithecina –

Genus Kenyapithecus –

Species Kenyapithecus wickeri [14 MYA]–

14 million years ago

Knuckle-walking mode of semi-terrestrial locomotion (McCrossin et al. 1998, p. 353-396)

Tribes Dryopithicini and Sivapithecini – introgression

“Since few great ape fossils have been found in Africa so far, ‘some scientists have forcefully suggested that the ancestors of African apes and humans must have emerged in Eurasia,’ said study senior author Gen Suwa, a palæoanthropologist at the University of Tokyo.” (Charles Q. Choi, LiveScience on February 12, 2016)

Subfamily Ponginae –

Tribe Sivapithecini –

Subtribe(s) N/A –

Genus Ankarapithecus

Genus Sivapithecus

Genus Gigantopithecus

Tribe Lufengpithecini –

Tribe Pongini –

Subtribe(s) N/A –

Genus Khoratpithecus

Species Khoratpithecus chiangmuanensis –

Species Khoratpithecus piriyai –

Species Khoratpithecus ayeyarwadyensi –

Genus Pongo

Subfamily Homininae – one of two extant chronosubfamilies to the Kenyapithecinae (the other being the Ponginae).

Tribe Dryopithicini – simultaneously the palæotribe to both Gorillini and Hominini, and may itself be a chronotribe of Kenyapithecini, resulting from hybridization between the Graecopithecina and the Kenyapithecina.

Hominine concestor (human-gorilla near-MRCA) – the near-to-last common ancestor of Homo and Gorilla, representing their first initial split into not-yet-completely-reproductively-isolated groups. Descendants of this near-to-last common ancestor would eventually become separable into two subtribes: Chororapithecina, the probable palæosubtribe of Gorillina, and Oreopithecina, a palæosubtribe to both Hominina and Panina. It is likely the Chororapithecina and Oreopithecina continued occasionally to either hybridize directly or otherwise benefit from indirect gene flow through intermediate populations.

Subtribe Dryopithecina

Genus Dryopithecus –

Genus Rudapithecus –

Genus Samburupithecus –

Subtribe ??? –

Genus Nakalipithecus –

Genus Anoiapithecus –

Subtribe Chororapithecina (my classification) – with Dryopithecini being a palæotribe of both Hominini and Gorillini, having existed at a time when it was not yet meaningful to distinguish basal members of Hominini and Gorillini at the tribe-level, this subtribe would be shared by the extant tribe Gorillini and its palæotribe Dryopithecini, but not by palæotribe Dryopithecini's other extant chronotribe Hominini. Chororapithecina may have begun as a hybrid population of the Graecopithecina with Kenyapithecina.

Genus Chororapithecus (Suwa et al., 2007) –

Species Chororapithecus abyssinicus – Also read: (Shigehiro et al., 2015)

Subtribe Oreopithecina (my classification) – with Dryopithicini being a palæotribe concestral to both Hominini and Gorillini, having existed at a time when it was not yet meaningful to distinguish basal members of Hominini and Gorillini at the tribe-level, this subtribe would be shared by the stem-hominin palæotribe Dryopithecini and its later chronotribe Hominini, but not by palæotribe Dryopithecini's other extant chronotribe Gorillini, and would be a palæosubtribe to both extant subtribe Hominina and extant subtribe Panina, having existed at a time when it was not yet meaningful to distinguish basal members of Hominina and Panina at the subtribe-level.

Genus Oreopithecus (Gervais, Paul 1872) –

Hypothetical mainland Oreopithecus (or similar) species –

Genus Orrorin –

Species Orrorin tugenensis –

Genus Sahelanthropus –

Species Sahelanthropus tchadensis –

Genus Ardipithecus –

Species Ardipithecus ramidus –

Species Ardipithecus kadabba –

Tribe Gorillini – one of two now-distinct modern chronotribes to palæotribe Dryopithecini, tribe Gorillini would include the modern subtribe Gorillina and its probable palæosubtribe Chororapithecina, but would not include Dryopithecini’s other subtribe, Oreopithecina, which was instead the palæosubtribe to Hominina and Panina.

Subtribe Chororapithecina (my classification) – with Dryopithecini being a palæotribe concestral to both Hominini and Gorillini, having existed at a time before it was meaningful to distinguish Hominini from Gorillini at the tribe-level, this subtribe would be shared by both the tribe Dryopithecini and its later chronotribe Gorillini, but not by Dryopithecini's other chronotribe Hominini, and would be a probable palæosubtribe to Gorillina (also my classification).

Subtribe Gorillina (my classification)

Genus Gorilla –

Tribe Hominini – one of two now-distinct modern chronotribes to palæotribe Dryopithecini, tribe Hominini includes the modern subtribes Hominina and Panina, as well as their concestral palæsubtribe Oreopithecina and the now-defunct subtribe Australopithecina.

Subtribe Oreopithecina (my classification) – having existed at a time before it was meaningful to distinguish basal members of the Hominina and Panina at the subtribe-level, this subtribe would be shared by both the extant tribe Hominini and its earlier chronotribe Dryopithecini, and would represent a palæosubtribe concestral to both subtribes Hominina and Panina.

Early Oreopithecins –

Hominin concestor (human-chimpanzee near-MRCA) – a progenitor that was the near-to-last common ancestor of Homo and Pan, excepting for occasional hybridization events subsequent to a “main split” into two distinct but initially non-reproductively-isolated lineages, the Hominina and Panina, perhaps best viewed at first as non-distinct yet artificially distinguishable sides of a “ring species”-like interfertility continuum, possibly involving clines.

Later Oreopithecins / early Hominina –

Subtribe Australopithecina – a now-defunct palæosubtribe to extant subtribe Hominina.

Genus Ardipithecus –

Genus Kenyanthropus –

Species Kenyanthropus platyops –

Genus Prænthropus –

Species Prænthropus anamensis –

Species Prænthropus afarensis –

Species Prænthropus bahrelghazali –

Species Prænthropus garhi –

Genus Australopithecus –

Species Australopithecus africanis –

Species Australopithecus deyiremeda –

Species Australopithecus garhi –

Species Australopithecus sediba –

Genus Paranthropus –

Species Paranthropus robustus –

Species Paranthropus boisei –

Early genus Homo –

Species Homo habilis –

Species Homo rudolfensis –

Subtribe Panina – a modern subtribe that includes descendants of its palæosubtribe, the Oreopithecini, that are more closely related to modern chimpanzees than to modern humans. Thus far, the chimpanzees and bonobos are the only known members, fossil or extant, of this subtribe.

Genus Pan – In a letter to Nature magazine, entitled First fossil chimpanzee, Sally McBrearty of the Department of Anthropology of the University of Connecticut and Nina G. Jablonski of the Department of Anthropology of the California Academy of Sciences state, “There are thousands of fossils of hominins, but no fossil chimpanzee has yet been reported. The chimpanzee (Pan) is the closest living relative to humans1. Chimpanzee populations today are confined to wooded West and central Africa, whereas most hominin fossil sites occur in the semi-arid East African Rift Valley. This situation has fuelled [sic] speculation regarding causes for the divergence of the human and chimpanzee lineages five to eight million years ago. Some investigators have invoked a shift from wooded to savannah vegetation in East Africa, driven by climate change, to explain the apparent separation between chimpanzee and human ancestral populations and the origin of the unique hominin locomotor adaptation, bipedalism2, 3, 4, 5. The Rift Valley itself functions as an obstacle to chimpanzee occupation in some scenarios6. Here we report the first fossil chimpanzee. These fossils, from the Kapthurin Formation, Kenya, show that representatives of Pan were present in the East African Rift Valley during the Middle Pleistocene, where they were contemporary with an extinct species of Homo. Habitats suitable for both hominins and chimpanzees were clearly present there during this period, and the Rift Valley did not present an impenetrable barrier to chimpanzee occupation.” (McBrearty & Jablonski, 2005)

Species Pan troglodytes –

Subspecies Pan troglodytes troglodytes –

Species Pan paniscus –

Subtribe Hominina – a modern subtribe that includes descendants of Hominina and Panina's shared palæosubtribe, the Oreopithecini, that are more closely related to modern humans than to modern chimpanzees and bonobos. This subtribe could be liberally defined to include stem hominins which “leaned toward the human side” of a “ring-species”-like continuum of interfertility that once existed facilitating gene flow between what were initially only semi-genetically-isolated lineages or groups, thus including creatures still capable of interbreeding with the ancestors of modern chimpanzees and bonobos either directly or via intermediate populations which still existed, or could be conservatively defined to only include creatures which were fully reproductively isolated from the ancestors of modern chimpanzees and bonobos. Such a conservative definition of Hominina becomes problematic, however, if genus Paranthropus should somehow be demonstrated to have been reproductively isolated from their contemporary ancestors of extant subtribe Panina, as the common ancestor of genus Homo and genus Paranthropus likely would not have been reproductively isolated from the their contemporary ancestors of Panina, thus making subtribe Homina a polyphyletic grouping.

Early Hominina- / late Oreopithecina – pr

Later Hominina –

Genus Meganthropus –

Genus Paranthropus –

Genus Homo –

Species Homo habilis –

Species Homo naledi –

Species Homo rudolfensis –

Species Homo ergaster –

Species Homo erectus –

Subspecies Homo erectus erectus –

Subspecies Homo erectus pekinensis

Subspecies Homo erectus yuanmouensis

Subspecies Homo erectus tautavelensis

Subspecies Homo erectus soloensis

Subspecies Homo erectus lantianensis

Subspecies Homo erectus nankinensis

Subspecies Homo erectus bilzingslebenensis

Subspecies Homo erectus palaeojavanicus

Subspecies Homo erectus georgicus

Species Homo palaeojavanicus –

Species Homo floresiensis –

Species Homo hiedelbergensis –

Subspecies Homo heidelbergensis antecessor –

Subspecies Homo heidelbergensis heidelbergensis –

Subspecies Homo heidelbergensis rhodesiensis –

Species Homo sapiens –

Subspecies Homo sapiens antecessor –

Subspecies Homo sapiens idaltu –

Subspecies Homo sapiens heidelbergensis –

Subspecies Homo sapiens rhodesiensis –

Subspecies Homo sapiens neanderthalensis –

Subspecies Homo sapiens sapiens –

V.a-2.) Doing Away with “Splitting”

Subfamily Homininae → genus Homo

• Genus Gorilla → species H. gorilla

• Genus Pan → species H. troglodytes

• Genus Homo → species Homo sapiens, Homo africanus, Homo afarensis

Genus Gorilla → species Homo gorilla

• Species Go. gorilla → species H. g. gorilla

• Species Go. graueri → subspecies H. g. graueri

Genus Pan → species Homo troglodytes

• Species P. troglodytes → subspecies H. tr. troglodytes

• Species P. paniscus → subspecies H. tr. paniscus

Genus Australopithecus → species Homo africanus, H. robustus, H. afarensis

• Species Au./Pr. anamensis → subspecies H. afr./afa. anamensis

• Species Au. afarensis / Pr. africanus → subspecies H. afr./afa afarensis

• Species Au./K. platyops → subspecies H. afr./afa. platyops/afarensis

• Species Au. africanus → subspecies H. afr. africanus

• Species Au./Pr. bahrelghazali → subspecies H. afr./afa. bahrelghazali

• Species Au./Pr. garhi → subspecies H. afr./afa. garhi

• Species Au. sediba → subspecies H. afr. sediba

• Species Au. antiquus → subspecies H. afr./afa. antiquus

• Species Au. habilis → subspecies H. afr. habilis

• Species Au./Par. aethiopicus → subspecies H. ro. aethiopicus

• Species Au. deyiremeda → subspecies H. afr./afa. deyiremeda

• Species Au./Par. robustus → subspecies H. ro. robustus

• Species Au./Par. boisei → subspecies H. ro. boisei

• Species Au./Par. walkeri → subspecies H. ro. walkeri

Genus Præanthropus → species Homo tugenensis, H. africanus, H. afarensis

• Species Pr./Orr. tugenensis → (sub)species H. (afa./afr.) tugenensis

• Species Pr./Au. anamensis → subspecies H. afr./afa. anamensis

• Species Pr./Au. africanus → subspecies H. afr./afa. afarensis

• Species Pr./Au. bahrelghazali → subspecies H. afr./afa. bahrelghazali

• Species Pr./Au. garhi → subspecies H. afr./afa. garhi

Genus Kenyanthropus → species Homo africanus, H. afarensis

• Species K./Au. platyops → subspecies H. afr./afa. platyops/afarensis

Genus Paranthropus → species Homo robustus

• Species Par./Au. aethiopicus → subspecies H. ro. aethiopicus

• Species Par./Au. robustus → subspecies H. ro. robustus

• Species Par./Au. boisei → subspecies H. ro. boisei

• Species Par./Au. walkeri → subspecies H. ro. walkeri

Genus Homo → species Homo sapiens, H. africanus, H. afarensis

• Species H. neanderthalensis → subspecies H. s. neanderthalensis

• Species H. heidelbergensis → subspecies H. s. heidelbergensis

• Species H. antecessor → subspecies H. s. antecessor

• Species H. floresiensis → subspecies H. s. floresiensis

• Species H. cepranensis → subspecies H. s. cepranensis

• Species H. erectus → various subspecies:

• Subspecies H. e. erectus → subspecies H. s. erectus

• Subspecies H. e. pekinensis → subspecies H. s. pekinensis

• Subspecies H. e. yuanmouensis → subspecies H. s. yuanmouensis

• Subspecies H. e. tautavelensis → subspecies H. s. tautavelensis

• Subspecies H. e. soloensis → subspecies H. s. soloensis

• Subspecies H. e. lantianensis → subspecies H. s. lantianensis

• Subspecies H. e. nankinensis → subspecies H. s. nankinensis

• Subspecies H. e. bilzingslebenensis → subspecies H. s. bilzingslebenensis

• Subspecies H. e. palaeojavanicus → subspecies H. afr./ro./s. palaeojavanicus

• Subspecies H. e. georgicus → subspecies H. afr./s. georgicus

• Species H. ergaster → subspecies H. s. ergaster

• Species H. rudolfensis → subspecies H. afr. rudolfensis

• Species H. naledi → subspecies H. afr. naledi

• Species H. habilis → subspecies H. afr. habilis

• Species H. antiquus → subspecies H. afr./afa. antiquus

Genus Meganthropus → species Homo sapiens, Homo africanus, Homo robustus

Genus Ardipithecus → species Homo ramidus, H. bamboli, H. fontani

• Species Ar. ramidus → subspecies H. ra./f./b. ramidus

• Species Ar. kadabba → subspecies H. ra. kadabba / H. f./b. ramidus

Genus Orrorin → species Homo tugenensis, H. afarensis, H. africanus

• Species Orr./Pr. tugenensis → (sub)species H. (afa./afr.) tugenensis

Genus Sahelanthropus → species Homo tchadensis

Genus Oreopithecus → species Homo bamboli, H. fontani

• Species Ore. bamboli → subspecies H. f./b. bamboli

Genus Chororapithecus → species Homo abyssinicus, H. fontani

• Species C. abyssinicus → (sub)species H. (f.) abyssinicus

Genus Samburupithecus → species Homo kiptalami, Homo fontani

• Species Sam. kiptalami → (sub)species H. (f.) kiptalami

Genus Dryopithecus → species Homo fontani, H. wuduensis, H. laietanus, H. crusafonti

• Species D. fontani → (sub)species H. (f.) fontani

• Species D. wuduensis → (sub)species H. (f.) wuduensis

• Species D. laietanus → (sub)species H. (f.) laietanus

• Species D. crusafonti → (sub)species H. (f.) crusafonti

Genus Anoiapithecus → species Homo brevirostris or H. fontani

• Species An. brevirostris → (sub)species H. (f.) brevirostris

Genus Nakalipithecus → species Homo nakayamai or H. fontani

• Species N. nakayamai → (sub)species H. (f.) nakayamai

Subfamily Ponginae → genus Pongo

• Genus Pongo → species Po. pygmæus

• Genus Sivapithecus → species Po. indicus

• Genus Gigantopithecus → species Po. blacki

Genus Sivapithecus → species Pongo indicus

• Species Siv. indicus → subspecies Po. i. indicus

• Species Siv. sivalensis → subspecies Po. i. sivalensis

• Species Siv. parvada → subspecies Po. i. parvada

Genus Gigantopithecus → species Pongo blacki

• Species Gi. blacki → subspecies Po. b. blacki

• Species Gi. giganteus → subspecies Po. b. giganteus

• Species Gi. bilaspurensis → subspecies Po. b. bilaspurensis

Subfamily Kenyapithecinae → genus Kenyapithecus

• Genus Ouranopithecus → species Ke. macedoniensis

• Genus Pierolopithecus → species Ke. catalaunicus

• Genus Græcopithecus → species Ke. freybergi

• Genus Kenyapithecus → species Ke. wickeri

Genus Ouranopithecus → species Kenyapithecus macedoniensis

• Species Ou. macedoniensis → species Ke. macedoniensis

Genus Pierolopithecus → species Kenyapithecus catalaunicus

• Species Pi. catalaunicus → species Ke. catalaunicus

Genus Græcopithecus → species Kenyapithecus freybergi

• Species Gr. freybergi → species Ke. freybergi

Genus Kenyapithecus → species Kenyapithecus wickeri

• Species Ke. wickeri → species Ke. wickeri

V.a-3.) Compromise

Family Hominidae

• Genus Homo

• Subgenus H. (Anthropus)

• Infragenus H. (A. Palæoanthropus)

• Species H. (A. Pa.) sapiens

• Subspecies H. (A. Pa.) s. sapiens

• Subspecies H. (A. Pa.) s. idaltu

• Species H. (A. Pa.) neanderthalensis

• Species H. (A. Pa.) heidelbergensis

• Species H. (A. Pa.) antecessor

• Infragenus H. (A. Pithecanthropus)

• Species H. (A. Pi.) floresiensis

• Species H. (A. Pi.) cepranensis

• Species H. (A. Pi.) erectus

• Subspecies H. (A. Pi.) e. erectus

• Subspecies H. (A. Pi.) e. pekinensis

• Subspecies H. (A. Pi.) e. yuanmouensis

• Subspecies H. (A. Pi.) e. tautavelensis

• Subspecies H. (A. Pi.) e. soloensis

• Subspecies H. (A. Pi.) e. lantianensis

• Subspecies H. (A. Pi.) e. nankinensis

• Subspecies H. (A. Pi.) e. bilzingslebenensis

• Subspecies H. (A. Pi.) e. palaeojavanicus

• Subspecies H. (A. Pi.) e. georgicus

• Species H. ergaster > subspecies H. s. ergaster

• Species H. rudolfensis > subspecies H. afr. rudolfensis

• Species H. naledi > subspecies H. afr. naledi

• Species H. habilis > subspecies H. afr. habilis

• Species H. antiquus > subspecies H. afr./afa. antiquus

• Subgenus H. (Australopithecus)

• Infragenus H. (Au. Gracilis)

• Species H.(Au. Gr.) habilis

• Subspecies H. (Au. Gr.) h. habilis

• Subspecies H. (Au. Gr.) h. rudolfensis

• Species H. (Au. Gr.) africanus

• Subspecies H.(Au. Gr.) afr. africanus

• Subspecies H. (Au. Gr.) afr. sediba

• Subspecies H. (Au. Gr.) afr. habilis

• Species H. (Au. Gr.) afarensis

• Subspecies H. (Au. Gr.) afa. anamensis

• Subspecies H. (Au. Gr.) afa. afarensis

• Subspecies H. (Au. Gr.) afa. platyops

• Subspecies H. (Au. Gr.) afa. bahrelghazali

• Subspecies H. (Au. Gr.) afa. garhi

• Subspecies H. (Au. Gr.) afa. antiquus

• Infragenus H. (Au. Paranthropus)

• Species H. (Au. Par.) aethiopicus

• Species H. (Au. Par.) deyiremeda

• Species H. (Au. Par.) robustus

• Species H. (Au. Par.) boisei

• Species H. (Au. Par.) walkeri

• Subgenus H. (Pan)

• Infragenus Not Applicable

• Species H. (Pan) troglodytes

• Species H. (Pan) paniscus

• Subgenus H. (Dryopithecus)

• Infragenus H. (D. Samburupithecus)

• Species H. (D. S.) kiptalami

• Infragenus H. (D. Anoiapithecus)

• Species H. (D. A.) brevirostris

• Infragenus H. (D. Nakalipithecus)

• Species H. (D. N.) nakayamai

• Infragenus H. (D. ?)

• Species H. (D. ?) fontani

• Species H. (D. ?) wuduensis

• Species H. (D. ?) laietanus

• Species H. (D. ?) crusafonti

• Subgenus H. (Chororapithecus)

• Infragenus Not Applicable

• Species H. (C.) abyssinicus

• Subgenus H. (Gorilla)

• Genus Pongo

• Subgenus P. (Gigantopithecus)

• Subgenus P. (Sivapithecus)

V.a-4.) Discussion of Approaches

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