Fossil analysis pushes back human split from other primates by two million years
A paper in the latest issue of the journal Nature suggests a common ancestor of apes and humans, Chororapithecus abyssinicus, evolved in Africa, not Eurasia, two million years earlier than previously thought.
“Our new research supports early divergence: 10 million years ago for the human-gorilla split and 8 million years ago for our split from chimpanzees,” said Los Alamos National Laboratory geologist and senior team member Giday WoldeGabriel. “That’s at least 2 million years earlier than previous estimates, which were based on genetic science that lacked fossil evidence.”
“Our analysis of C. abyssinicus fossils reveals the ape to be only 8 million years old, younger than previously thought. This is the time period when human and African ape lines were thought to have split, but no fossils from this period had been found until now,” WoldeGabriel said.
According to the paper, C. abyssinicus revealed answers about gorilla lineage but also provided fossil evidence that our common ancestor migrated from Africa, not Eurasia, where fossils were more prolific prior to this discovery of multiple skeletons. While some skeptics say that more fossil evidence is needed before they accept this team’s conclusions, many agree that the discovery of a fossil ape from this time period is important since only one other had been found. More.
Wouldn’t bet the rent on this but it raises a question: If it were really true that the human genome shows 98%-99% similarity with the chimpanzee after all these years, that is quite a lot of stasis. No?
See also: Stasis: Life goes on but evolution does not happen
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Here’s the abstract:
The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidation of African ape and human origins, but few fossil assemblages of this period have been reported from sub-Saharan Africa. Since the 1970s, the Chorora Formation, Ethiopia, has been widely considered to contain ~10.5 million year (Myr) old mammalian fossils1, 2, 3, 4, 5, 6, 7. More recently, Chororapithecus abyssinicus, a probable primitive member of the gorilla clade6, was discovered from the formation. Here we report new field observations and geochemical, magnetostratigraphic and radioisotopic results that securely place the Chorora Formation sediments to between ~9 and ~7?Ma. The C. abyssinicus fossils are ~8.0?Myr old, forming a revised age constraint of the human–gorilla split. Other Chorora fossils range in age from ~8.5 to 7?Ma and comprise the first sub-Saharan mammalian assemblage that spans this period. These fossils suggest indigenous African evolution of multiple mammalian lineages/groups between 10 and 7?Ma, including a possible ancestral-descendent relationship between the ~9.8?Myr old Nakalipithecus nakayamai8 and C. abyssinicus. The new chronology and fossils suggest that faunal provinciality between eastern Africa and Eurasia had intensified by ~9?Ma, with decreased faunal interchange thereafter9, 10, 11, 12. The Chorora evidence supports the hypothesis of in situ African evolution of the Gorilla–Pan–human clade, and is concordant with the deeper divergence estimates of humans and great apes based on lower mutation rates of ~0.5?×?10-9 per site per year (refs 13, 14, 15). (paywall) – Shigehiro Katoh, Yonas Beyene, Tetsumaru Itaya, Hironobu Hyodo, Masayuki Hyodo, Koshi Yagi, Chitaro Gouzu, Giday WoldeGabriel, William K. Hart, Stanley H. Ambrose, Hideo Nakaya, Raymond L. Bernor, Jean-Renaud Boisserie, Faysal Bibi, Haruo Saegusa, Tomohiko Sasaki, Katsuhiro Sano, Berhane Asfaw, Gen Suwa. New geological and palaeontological age constraint for the gorilla–human lineage split. Nature, 2016; 530 (7589): 215 DOI: 10.1038/nature16510