A new relative joins Lucy on the human family tree. An international team of scientists, led by Curator of Physical Anthropology Dr. Yohannes Haile-Selassie, has discovered a 3.3 to 3.5 million-year-old new human ancestor species. Upper and lower jaw fossils recovered from the Woranso-Mille area of the Afar region of Ethiopia have been assigned to the new species Australopithecus deyiremeda. This hominin lived alongside the famous Lucy’s species, Australopithecus afarensis. The species will be described in the May 28, 2015 issue of the international scientific journal Nature.
Australopithecus deyiremeda differs from Lucy’s species in terms of the shape and size of its thick-enameled teeth and the robust architecture of its lower jaws. The anterior teeth are also relatively small indicating that it probably had a different diet.
The new species is yet another confirmation that Lucy’s species, Australopithecus afarensis, was not the only potential human ancestor species that roamed in what is now the Afar region of Ethiopia during the middle Pliocene, said lead author and Woranso-Mille project team leader Dr. Yohannes Haile-Selassie. Current fossil evidence from the Woranso-Mille study area clearly shows that there were at least two, if not three, early human species living at the same time and in close geographic proximity.
This new species from Ethiopia takes the ongoing debate on early hominin diversity to another level, said Haile-Selassie. Some of our colleagues are going to be skeptical about this new species, which is not unusual. However, I think it is time that we look into the earlier phases of our evolution with an open mind and carefully examine the currently available fossil evidence rather than immediately dismissing the fossils that do not fit our long-held hypotheses, said Haile-Selassie.
By the time scientists figure out just where a new specimen fits, the media have lost all interest and most folks don't get the details of how the initial claims have been narrowed down.
KNM-ER-1470 is a good example. The dates and assignments have both changed (more than once) since the initial announcement back when I was studying fossil man in graduate school.
Louis Leakey saw KNM-ER 1470 only days before his death, and, believing the skull to be a million years older than it was, classified it as an indeterminate species of Homo. When scientists later dated the skull to 1.9 million years old, the same age to when Homo habilis lived, the scientific community thought KNM-ER 1470 must then belong to Homo habilis - but the mandible (jaw) and teeth just didn’t seem to fit within acceptable limits of variation or differences for H. habilis. Even if KNM-ER 1470 was considered a large H. habilis male, the size difference would be too great compared to KNM-ER 1813, an established H. habilis female, for the two to both belong to the same species. Over several weeks following its discovery, scientists Meave Leakey and Bernard Wood reconstructed KNM-ER 1470’s skull from more than 150 fragments, revealing a large cranium with a long, wide, flat face. While tooth roots show that this early human had large teeth, the skull lacked the massive jaw muscle features characteristic of robust australopithecines.
Today, most scientists now accept KNM-ER 1470 as belonging to Homo rudolfensis -- as species that co-existed in the Turkana Basin, northern Kenya, with three other species sometime between 2.0 and 1.5 million years ago: Homo habilis, Homo erectus, and Paranthropus boisei.
KNM-ER 1470 Exhibit item Site: Koobi Fora, Kenya Date of discovery: 1972 Discovered by: Bernard Ngeneo Age: About 1.9 million years old Species: Homo rudolfensis
They also have an interactive bit where you can compare features, and some 3D displays that you can rotate.
They don't list A. deyiremeda yet and the article doesn't give the fossil identification, all it gives is
quote:
Cast of the holotype upper jaw of Australopithicus deyiremeda ...
They have a couple of specimens so far. Hopefully they will find more soon to help sort this out.
quote: ... Yohannes Haile-Selassie, curator and head of the physical anthropology department at the Cleveland Museum of Nature History, and his colleagues, announced a new 3.3-million-year-old species of human ancestor contemporaneous with Au.afarensis and living (as Lucy did) in the Afar region of what is now Ethiopia: Australpithecus deyiremeda. (The word "deyiremeda" means "close relative" in the local Afar language.)
Whether you find this news surprising depends, in part, on whether you're a lumper or splitter. The Wikipedia definition of these terms works well for our purposes:
"A 'lumper' is an individual who takes a gestalt view of a definition, and assigns examples broadly, assuming that differences are not as important as signature similarities. A 'splitter' is an individual who takes precise definitions, and creates new categories to classify samples that differ in key ways."
Haile-Selaisse et al.'s decision to create a new category for this East African hominin comes from the splitter camp and is bold (though certainly not unprecedented) given that the fossil material they uncovered consists entirely of jaws and teeth. These scientists are confident that there's adequate morphological variation in the maxilla (upper jaw), mandible (lower jaw) and teeth compared to earlier-described hominins to justify the new species designation. ...
An assertion that Au. deyiremeda is a new species equates, then, to an assertion that it could not have interbred with other hominins living nearby at the time. For White, this causes concern:
White's two points resonate with me, especially the idea that naming a new species means that scientists automatically make probably premature statements about relationships among hominins.
It seems to me that if you have two contemporaneous populations with morphologically distinct features that that would be evidence of genetic isolation.
But when one of your populations consists of three partial jaws, the question is whether it is in a fact a distinct population ...
And I would agree, were it not that there are quite a number of fossils of the other australopithecines iirc, and that these purportedly fall outside those fossils.
However I see this as part of the peer review process -- an hypothetical suggestion is made and it is reviewed by others in the field, the hypothesis is tested against the known information and predictions of future finds are made to either confirm or refute it.
Maybe I like to think of evolution as bushy rather than linear, or maybe like an ivy with a lot of tendrils that branch off.
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