New Findings Solve Human Origins Mystery

An extraordinary advance in human origins
research reveals evidence of the emergence of the upright human body plan
over
15 million years earlier than most experts have believed. More
dramatically, the study confirms preliminary evidence that many early
hominoid apes
were most likely upright bipedal walkers sharing the basic body form of
modern humans. On October 10th, online, open-access journal PLoS ONE will
publish the report based on research from Harvard University's Museum of
Comparative Zoology and from the Cedars Sinai Institute for Spinal
Disorders that connects several recent fossil discoveries to older fossils
finds that have eluded adequate explanation in the past.



Recent advances in the field of homeotic genetics together with a series
of discoveries of hominoid fossils vertebrae now strongly suggest that a
specific genetic change that generated the upright bipedal human body form
may soon be identified. The various upright "hominiform" hominoids
appear to share this morphogenetic innovation with modern humans.
Homeotics concerns the embryological assembly program for midline
repeating
structures such as the human vertebral column and the insect body
segments.



The report analyses changes in homeotic embryological assembly of the
spine in more than 200 mammalian species across a 250 million year time
scale.
It identifies a series of modular changes in genetic assembly program that
have taken place at the origin point of several major groups of mammals
including the newly designated 'hominiform' hominoids that share the
modern human body plan.



The critical event involves a dramatic embryological change unique to the
human lineage that was not previously understood because the unusual human
condition was viewed as "normal."



"From an embryological point of view, what took place is literally
breathtaking," says Dr. Aaron Filler, a Harvard trained evolutionary
biologist
and a medical director at Cedars Sinai Medical Center's Institute for
Spinal Disorders. Dr. Filler is an expert in spinal biology and the author
of
three books about the spine - "Axial Character Seriation in Mammals"
(BrownWalker 2007), "The Upright Ape" (New Page Books 2007), and "Do
You Really Need Back Surgery" (Oxford University Press 2007).



In most vertebrates (including most mammals), he explains, the dividing
plane between the front (ventral) part of the body and the back (dorsal)
part
is a "horizontal septum" that runs in front of the spinal canal. This is a
fundamental aspect of animal architecture. A bizarre birth defect in
what may have been the first direct human ancestor led to the
"transposition" of the septum to a position behind the spinal cord in the
lumbar
region. Oddly enough, this configuration is more typical of invertebrates.



The mechanical effect of the transposition was to make horizontal or
quadrupedal stance inefficient. "Any mammal with this set of changes would
only
be comfortable standing upright. I would envision this malformed young
hominiform - the first true ancestral human - as standing upright from a
young age while its siblings walked around on all fours."
















The earliest example of the transformed hominiform type of lumbar spine is
found in Morotopithecus bishopi an extinct hominoid species that lived in
Uganda more than 21 million years ago. "From a number of points of view,"
Filler says, "humanity can be redefined as having its origin with
Morotopithecus. This greatly demotes the importance of the bipedalism of
Australopithecus species such as Lucy (Australopithecus afarensis) since
we
now know of four upright bipedal species that precede her, found from
various time periods on out to Morotopithecus in the Early Miocene."



The paper in PLoS ONE is entitled: "Homeotic evolution in the mammalia:
Diversification of therian axial seriation and the morphogenetic basis of
human origins."




Citation: Filler AG (2007) Homeotic Evolution in the Mammalia:
Diversification of Therian Axial Seriation and the Morphogenetic Basis of
Human
Origins. PLoS ONE 2(10): e1019. doi:10.1371/journal.pone.0001019

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the
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