Newly Found Fossils, Same Old Puzzle

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September 02, 2012

A Nature paper in early August announced the finding of  dramatic fossils and refocused attention on the significance of fossils found decades ago.  The team led by Meave Leakey said bones found at Koobi Foora near the shores of Lake Turkana resembled those found forty years ago near this same location.

in 1972, a team led by Richard Leakey (the husband of Meave Leakey) and Alan Walker uncovered bones they attributed to a new species, Homo rudolfensis. they designated their find ER 1470 (“ER" standing for East Rudolph, Lake Turkana then being known as Lake Rudolph). The announcement last month by Meave Leakeyrevitalizes the questions puzzling scientists trying to make sense of the scrappy evidence for early Homo in the period before the emergence of Homo erectus.

Fragments of a juvenile face and jaw, excavated between 2007 and 2009, have been greeted with great interest and renewed controversy, as set forth in commentary accompanying the paper by leakey, Spoor et al.in nature.  A complete discussion of this can be found at the following references:

New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo by Meave Leakey et al. the abstract oif which reads,

“Since its discovery in 1972 (ref. 1), the cranium KNM-ER 1470 has been at the centre of the debate over the number of species of early Homo present in the early Pleistocene epoch2 of eastern Africa. KNM-ER 1470 stands out among other specimens attributed to early Homo because of its larger size, and its flat and subnasally orthognathic face with anteriorly placed maxillary zygomatic roots3. This singular morphology and the incomplete preservation of the fossil have led to different views as to whether KNM-ER 1470 can be accommodated within a single species of early Homo that is highly variable because of sexual, geographical and temporal factors4, 5, 6, 7, 8, 9, or whether it provides evidence of species diversity marked by differences in cranial size and facial or masticatory adaptation3, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20. Here we report on three newly discovered fossils, aged between 1.78 and 1.95 million years (Myr) old, that clarify the anatomy and taxonomic status of KNM-ER 1470. KNM-ER 62000, a well-preserved face of a late juvenile hominin, closely resembles KNM-ER 1470 but is notably smaller. It preserves previously unknown morphology, including moderately sized, mesiodistally long postcanine teeth. The nearly complete mandible KNM-ER 60000 and mandibular fragment KNM-ER 62003 have a dental arcade that is short anteroposteriorly and flat across the front, with small incisors; these features are consistent with the arcade morphology of KNM-ER 1470 and KNM-ER 62000. The new fossils confirm the presence of two contemporary species of early Homo, in addition to Homo erectus, in the early Pleistocene of eastern Africa.“

See  Bernard Wood’s commentary in the same issue of Nature

See also Science News, August 8th, 201, New fossils hint at ancestral split African discoveries point to two early species in the human genus by Bruce Bower.