Origin of the hominidae: The record of african large hominoid evolution between 14 my and 4 my

Abstract

The Hominidae probably originated in Africa sometime between 14 my and 4 my ago. Unfortunately the fossil evidence from this time period and region is relatively poor. We regard only 11 specimens as unambiguous hominoids, and none preserves a great amount of anatomy. They come from a very restricted geographical region. Two are from Ethiopia and the rest from Kenya, where most have been found in the Tugen Hills succession west of Lake Baringo. No unequivocal fossil evidence of ancestral Gorilla or Pan has yet been recognised. The oldest hominid yet known-in the sense used here-probably dates to greater than 5.6 my. One especially interesting question in the paleobiology of the hominoidea, as in other taxa, is the relation of extrinsic factors to speciation. To resolve this issue, diagnostic and well-dated specimens are necessary. However, they need not be anatomically spectacular. Fragmentary specimens, although imperfect anatomically, can be just as effective as more complete material in defining taxonomic branching points. The origin of Hominidae, or at least bipedalism, has been conjecturally associated with a regional environmental change from tropical forest to widespread grassland. Evidence accumulating from various parts of Africa, particularly the Tugen Hills, suggests this was not an abrupt transition. The pattern of habitats was probably patchy in space and time. This may have been a factor in the origin and development of the hominid clade. Much progress has recently been made, but further hominoid specimens, coupled with environmental information from well-calibrated sequences, is necessary to elucidate the nature and causes of cladistic branching within the superfamily .Some perennial problems in human evolution are the basic ones. Where did the first hominid species diverge from other hominoids? When did this event take place? What did the first hominid look like? And what were the proximate causes of the divergence and subsequent radiation of the Hominidae?It is easier to answer some of these questions than others, at least in a general way. With regard to the location of human evolution, selective quotation often attributes to Darwin the perception, now believed to be correct, that hominids evolved in Africa. In The Descent of Man (1871), having pointed out the general relation between extinct and extant species in each great region of the world, Darwin writes with typical caution:"It is therefore probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species 0 1988 Alan R. Liss, Inc. [Vol. 31, 1988 are now man's nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere." YEARBOOK OF PHYSICAL ANTHROPOLOGYOf course, at that time the fossil record of our early progenitors was somewhat sparse, but not nonexistent, and Darwin was even more circumspect and astute than this isolated reference implies. In the less-cited following passage he continues: "But it is usele...

Resolution of the African hominoid trichotomy by use of a mitochondrial gene sequence.

“…This branch length variation can be interpreted in terms of evolutionary divergence times. Assuming molecular rates are clock-like and Homo and Pan lineages diverged, for example, about 6 million years ago (52), the Gorilla lineage divergence would be dated at 7.9-10.0 million years according to COII and 28S rRNA gene sequences and DNA hybridization data, but at 6.6-7.0 million years by previous DNA sequence data sets. nonprimates.…”

Sivapithecus is east and Dryopithecus is west, and never the twain shall meet

“…The isolated teeth from Ngorora have been described as having affinities primarily with the Proconsuloidea or middle Miocene East African hominoids (e.g. Equatorius) (Hill and Ward, 1988;Begun, 2001;Hill et al, 2002).…”

A new Late Miocene great ape from Kenya and its implications for the origins of African great apes and humans

“…hominoid evolution R ecent molecular studies suggest that the divergence between humans and chimpanzees occurred at 7-5 Ma and that the divergence of gorillas occurred at 9-8 Ma (1-4). Consequently, the Late Miocene is the crucial period for understanding the origins of African great apes and humans, but unfortunately the African hominoid fossil record is extremely poor after 13 Ma (5,6). A rare exception is Samburupithecus kiptalami (9.6 Ma), discovered from Samburu Hills, northern Kenya (7,8).…”