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Tuesday, March 29, 2016

Australopithecus fossils found east of the Great Rift Valley 

New fossils from Kenya suggest that an early hominid species — 
Australopithecus afarensis — lived far eastward beyond the Great Rift 
Valley and much farther than previously thought. An international team 
of paleontologists led by Emma Mbua of Mount Kenya University and 
Masato Nakatsukasa of Kyoto University report findings of fossilized 
teeth and forearm bone from an adult male and two infant A. afarensis 
from an exposure eroded by the Kantis River in Ongata-Rongai, a 
settlement in the outskirts of Nairobi. 

"So far, all other A. afarensis fossils had been identified from 
the center of the Rift Valley," explains Nakatsukasa. "A previous 
Australopithecus bahrelghazali discovery in Chad confirmed that 
our hominid ancestor's distribution covered central Africa, but 
this was the first time an Australopithecus fossil has been found 
east of the Rift Valley. This has important implications for what 
we understand about our ancestor's distribution range, namely that 
Australopithecus could have covered a much greater area by this 
Stable isotope analysis revealed that the Kantis region was humid, 
but had a plain-like environment with fewer trees compared to other 
sites in the Great Rift Valley where A. afaransis fossils had 
previously appeared. "The hominid must have discovered suitable 
habitats in the Kenyan highlands. It seems that A. afaransis was 
good at adapting to varying environments," notes Nakatsukasa. 
Kantis: A new Australopithecus site on the shoulders of the 
Rift Valley near Nairobi, Kenya 


Most Plio-Pleistocene sites in the Gregory Rift Valley that have 
yielded abundant fossil hominins lie on the Rift Valley floor. Here 
we report a new Pliocene site, Kantis, on the shoulder of the 
Gregory Rift Valley, which extends the geographical range of 
Australopithecus afarensis to the highlands of Kenya. This species, 
known from sites in Ethiopia, Tanzania, and possibly Kenya, is 
believed to be adapted to a wide spectrum of habitats, from open 
grassland to woodland. The Kantis fauna is generally similar to that 
reported from other contemporaneous A. afarensis sites on the Rift 
Valley floor. However, its faunal composition and stable carbon 
isotopic data from dental enamel suggest a stronger C4 environment 
than that present at those sites. Although the Gregory Rift Valley 
has been the focus of paleontologists' attention for many years, 
surveys of the Rift shoulder may provide new perspective on African 
Pliocene mammal and hominin evolution. 

-Thanks to Rick Trasky for these articles.

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