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June 03, 2013

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Human lineage had diverse offshoots, study finds

Aug. 8, 2012
Courtesy of Nature
and World Science staff

At least two dif­fer­ent spe­cies of hu­mans lived along­side our own an­ces­tors in Af­ri­ca al­most two mil­lion years ago, show­ing the hu­man line­age was more di­verse than pre­vi­ously thought, new re­search in­di­cates.

The fos­sils from north­ern Ken­ya, dat­ed to be­tween 1.78 and 1.95 mil­lion years ago, are de­scribed in the cur­rent is­sue of the re­search jour­nal Na­ture.

“These three fos­sils show that two spe­cies of the ge­nus Ho­mo, our own ge­nus, lived along­side our di­rect an­ces­tor Ho­mo erec­tus, nearly two mil­lion years ago,” said an­thro­po­l­o­gist Meave Lea­key of the Nai­ro­bi, Ken­ya-based Turkana Ba­sin In­sti­tute, in a tel­e­phone brief­ing dis­cussing the find­ings.

“They are sig­nif­i­cant be­cause they an­swer a key ques­tion in our ev­o­lu­tion­ary past: How di­verse is our ge­nus close to the base of the hu­man line­age?” she said.

This ques­tion first “came in­to sharp fo­cus with the dis­cov­ery in 1972 of an al­most com­plete skull, KNM-ER 1470 or 1470 for short,” she added. “This skull is strik­ing with its re­markably long, flat face and large brain. But be­cause 1470 lacked teeth, and a low­er jaw, it raised the ques­tion as to wheth­er it rep­re­sented a dif­fer­ent spe­cies” from Ho­mo erec­tus.

The skull re­mained at the cen­ter of an un­re­solved de­bate as fur­ther ev­i­dence re­mained “frus­trat­ingly elu­sive” for dec­ades af­ter­wards, she added.

But “in 2007, our luck mag­ic­ally changed, and with­in three years, we found three fos­sils, which we be­lieve are at­trib­ut­a­ble to the same spe­cies as 1470,” she added. All three come from with­in 6 miles or 10 km of where the pre­vi­ous one had been found.

The face is “re­markably si­m­i­lar to that of 1470, but small­er,” she added. “The new fos­sils tell us for the first time what the teeth and low­er jaw of 1470 would have looked like and en­a­ble us to sep­a­rate the col­lec­tion of non-Ho­mo erec­tus fos­sils in­to two groups with clear, dis­tin­guish­ing char­ac­ters.”

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At least two different species of humans lived alongside our own ancestors in Africa almost two million years ago, showing the human lineage was more diverse than previously thought, new research indicates. The fossils from Northern Kenya, dated to between 1.78 and 1.95 million years ago from northern Kenya, are described in the current issue of the research journal Nature. “These three fossils show that two species of the genus Homo, our own genus, lived alongside our direct ancestor Homo erectus, nearly two million years ago,” said anthropologist Meave Leakey of the Nairobi, Kenya-based Turkana Basin Institute, in a telephone briefing discussing the findings. “They are significant because they answer a key question in our evolutionary past: How diverse is our genus close to the base of the human lineage?” she said. This question first “came into sharp focus with the discovery in 1972 of an almost complete skull, KNM-ER 1470 or 1470 for short,” she added. “This skull is striking with its remarkably long, flat face and large brain. But because 1470 lacked teeth, and a lower jaw, it raised the question as to whether it represented a different species” from Homo erectus. The skull remained at the center of an unresolved debate as further evidence remained “frustratingly elusive” for decades afterwards, she added. But “in 2007, our luck magically changed, and within three years, we found three fossils, which we believe are attributable to the same species as 1470,” she added. All three come from within 6 miles or 10 km of where the previous one had been found. The face is “remarkably similar to that of 1470, but smaller,” she added. “The new fossils tell us for the first time what the teeth and lower jaw of 1470 would have looked like and enable us to separate the collection of non-Homo erectus fossils into two groups with clear, distinguishing characters.”