Marc Verhaegen wrote:
Supraorbital morphology and social dynamics in human evolution
Nature Ecology & Evolution 2
doi 10.1038/s41559-018-0528-0
Ricardo Miguel Godinho, Penny Spikins & Paul O'Higgins 2018
The REAL abstract
https://www.nature.com/articles/s41559-018-0528-0
Supraorbital morphology and social dynamics
in human evolution
Abstract
Uniquely, with respect to Middle Pleistocene
hominins, anatomically modern humans do not
possess marked browridges, and have a more
vertical forehead with mobile eyebrows that
play a key role in social signalling and
communication. The presence and variability
of browridges in archaic Homo species and
their absence in ourselves have led to debate
concerning their morphogenesis and function,
with two main hypotheses being put forward:
that browridge morphology is the result of
the spatial relationship between the orbits
and the brain case; and that browridge
morphology is significantly impacted by biting
mechanics. Here, we virtually manipulate the
browridge morphology of an archaic hominin
(Kabwe 1), showing that it is much larger than
the minimum required to fulfil spatial demands
and that browridge size has little impact on
mechanical performance during biting. As
browridge morphology in this fossil is not
driven by spatial and mechanical requirements
alone, the role of the supraorbital region in
social communication is a potentially
significant factor. We propose that conversion
of the large browridges of our immediate
ancestors to a more vertical frontal bone in
modern humans allowed highly mobile eyebrows
to display subtle affiliative emotions.
Archaic Homo's litoral phase required hydrodynamic platycephaly
(requiring an eye-protecting supra-orbital torus),
Just like in whales -except that whales don't have a
"eye-protecting supra-orbital torus". No brow ridges
there.
Nor in dolphins, porpoises, etc
Or beavers. Otters. Seals. Manatees. Walruses.
Etc
But other primates have brow ridges...
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