Saturday, September 14, 2019

Time to jettison the "common ancestry" theory?

A. anamensis skull

Archaic humans show a range of physical features that are found in modern humans. Those features include high broad foreheads, low receding foreheads, low cheek bones, high cheek bones, protruding chin, cranial size generally proportional to body size, dentition within the range of primitive and modern humans, and hands and feet like modern humans.

That assessment of the data is leading paleoanthropologists to rethink the prevailing evolutionary theory, according to this recent statement made by Hester Hanegraef.
"Discoveries all over the world in the last decade have led to a complete rethinking of our evolutionary past. It shows that new fossils do not always support existing hypotheses, and that we must be prepared to change our views and formulate new theories based on the evidence at hand."

Note the protruding jaw of this eighth century BC blacksmith.

The 1500 bones and bone fragments recovered by the Rising Star Expedition belonged to at least 15 individuals. The adults were about 5 feet tall. Parts of the skeletons resemble modern human anatomy while other skeletal remains resemble the australopiths, like Lucy. In other words, this burial pit contained the remains of people who ranged in appearance about as much as modern humans.The bones/bodies were ritually deposited over “some period of time.”

This 250,000 year hand of Homo naledi is virtually identical to that of modern humans.

This find is being presented as a "new branch" of homo, called Homo naledi. H. naledi is viewed as slightly more human than the A. australopithecine and slightly less human than modern humans.

Jeffrey Schwartz thinks that the H. naledi remains represent two or more different species. He makes his case in Newsweek: “Why the Homo Naledi Discovery May Not Be Quite What it Seems”

On the other hand, John Hawks states that "The variation within the collection is not high, it is extraordinarily low." Hawks reports: "Homo naledi has a mosaic of features that include some that compare most closely to more primitive australopiths, and others that compare more closely to Homo. How do we know that this is one species rather than a jumble of species mixed together? Simple: every feature that is repeated in the sample is nearly identical in all individuals that preserve it."

Similar speculation arises around A. anamensis. This find has been in the news this week. A. anamensis lived approximately between 4.2 and 3.8 million years ago. Nearly one hundred fossil specimens are known from Kenya and Ethiopia, representing over 20 individuals.

The shape of the end of this lower leg bone, or tibia, indicates that A. anamensis walked upright. Most features align with those identified with A afarensis. The teeth in this jawbone are large relative to the body size of A. anamensis. The back teeth are also large relative to the front teeth. Both primitive traits are characteristic of all Australopithecus.

Hester Hanegraef notes that A. anamensis and A. afarensis overlap for at least 100,000 years, "making it impossible for A. afarensis to have evolved gradually from one single ancestral group. In fact, it is becoming increasingly obvious that most species on our evolutionary lineage likely evolved by branching off from existing groups." (Read more here.)

The question remains: Do these early Homo fossils represent stages or branches of evolutionary development from a common ancestor, or do they represent archaic humans with the same range of physical diversity as modern humans?

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