Human facial morphology changed significantly throughout hominin evolution due to dietary and climate pressures
the verdict
INSUFFICIENT LEANING
refutedsupported
the weight of evidence
4 sources for · 0 against
Four sources partially discuss aspects of hominin evolutionary history and facial morphology, but they do not provide sufficient counted support for the specific claim regarding dietary and climate pressures.
I posit that humans appear to be the only species that develops otitis media. If animals in the wild had developed middle-ear disease to any significant degree, they would have been selected out during evolution because they would not have survived their predators given the associated hearing loss. Why do humans have otitis media? Evolution has had a significant impact. It is well known that humans are born 12 months too early, which is the result of adaptations to bipedalism and our big brain that, over time, resulted in a relatively small female pelvic outlet compared with nonhuman primates. As a consequence of too early a birth, not only is our immune system immature, but the eustachian tube is too short and floppy in the first year of life. But why is otitis media still common in older individuals? What other adaptation is uniquely human? We developed speech that was associated with descent of the larynx and hyoid bone, which, along with a decrease in prognathism (i.e., facial flattening), resulted in a change in palatal morphology as compared with other primates. Comparative anatomic and physiologic studies have demonstrated significant differences between humans and monkeys, especially in the muscles of the eustachian tube. Paradoxic constriction, as apposed to dilation, on swallowing is a common tubal dysfunction in humans and certain monkey models with chronic middle-ear effusion. My hypothesis is that chronic otitis media with effusion in patients with tubal constriction is a consequence of adaptation for speech and that, most likely, the levator veli palatini muscle is the cause.
The pathogenesis of otitis media is multifactorial, but the role of evolution on its development has not been addressed. We posit that the high prevalence of middle‐ear disease is most likely restricted to humans, in contrast to other wild species, because the associated hearing loss would have reduced the fitness of affected individuals as a result of predation. We present here the possible consequences of two human adaptations that may have resulted in ubiquitous otitis media: the interaction of bipedalism and increased brain size, and the loss of facial prognathism resulting from speech or cooking. As a consequence of our adaptation for bipedalism, the female pelvic outlet is constricted, which, in the context of a rapidly enlarging brain, results in humans being born 12 months too soon. Significantly, immature eustachian tube structure and function, in conjunction with an immature immune system, helps to explain the high incidence of otitis media in the first year of life. But the persistence of middle‐ear disease beyond this stage is not explained by “immaturity.” The morphology of the palate changed with the adaptations that produced facial flattening, with concomitant effects on eustachian tube function. These changes resulted in relatively poor human physiologic tubal function in comparison to the nonhuman primate.
Fossils of H. erectus have been found in India, China, Java, and Europe, and were known in the past as “Java Man” or “Peking Man.” H. erectus had a number of features that were more similar to modern humans than those of H. habilis. H. erectus was larger in size than earlier hominins, reaching heights up to 1.85 meters and weighing up to 65 kilograms, which are sizes similar to those of modern humans. Its degree of sexual dimorphism was less than in earlier species, with males being 20 to 30 percent larger than females, which is close to the size difference seen in our own species. H. erectus had a larger brain than earlier species at 775 to 1,100 cubic centimeters, which compares to the 1,130 to 1,260 cubic centimeters seen in modern human brains. H. erectus also had a nose with downward-facing nostrils similar to modern humans, rather than the forward-facing nostrils found in other primates. Longer, downward-facing nostrils allow for the warming of cold air before it enters the lungs and may have been an adaptation to colder climates. Artifacts found with fossils of H. erectus suggest that it was the first hominin to use fire, hunt, and have a home base. H.
Adam Wilkins discussed his new book, "Making Faces: The Evolutionary Origins of the Human Face." Human ancestors--traced back to primate species which lived over 60 million years ago--had typical mammalian faces that were fur-covered, with muzzles and sloping heads. However, the physical features and degree of expressiveness in a human face is highly unusual among mammals today. This lecture identified distinctive features of the human face, explored how and why our unique facial features evolved and detailed the critical role facial expression plays in human society.
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