ASB 194 lect14.doc

ASB 194 lect14.doc - Lect14 Later Evolution of Homo Homo...

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Lect14 Later Evolution of Homo Homo erectus had a much larger brain , larger body , but smaller teeth than Australopithecines. Homo sapiens has a larger brain still, but a less robust body and smaller teeth than Homo erectus. These traits may indicate an increasing reliance on tools. Many paleoanthropologists now believe that Homo erectus split into two species later during its time period. Asian H. erectus fossils have smaller brains, thicker skulls, and more sloped skull throughout their time range. They don’t seem to evolve much in the direction of modern H. sapiens. Most importantly, Asian forms never develop the use of Achuelian tools common in western sites. Instead they retained the primitive Oldowan style toolkit until only a couple hundred thousand years ago! African and European H. erectus on the other hand show traits that seem transitional to later H. sapiens. Scientists who believe this split is big enough to separate out two species call the H. erectus forms in Africa and Europe, Homo ergaster . Later H. ergaster may evolve into a third species in Europe (H. heidelbergensis). I. Homo erectus traits for which their is less physical evidence: A) Projecting nose . The shape of the nasal hollow suggests that H. erectus is the first hominid to have a projecting nose like modern humans. This may be useful in hot dry climates for brain cooling and air humidification. It is also useful in colder dry climates. B) LOSS OF BODY HAIR --this is related to changes in ways of managing heat build-up in the body 1) mammals with hair lose body heat by RADIATION, that is, heat radiates from the body--also, cooling by panting, holding tongue out 2) fur or hair can be an effective insulation against solar heat, as long as animal doesn't build up to much internal heat through running or other work in full sunlight. But for diurnal animals that do work in hot temperatures another way of losing heat is through CONDUCTION via EVAPORATION of SWEAT. Internal body heat is conducted to the surface of the skin through contact with moisture on the skin--evaporation dissipates the heat. This works best on hairless skin, since hair would tend to move the sweat off the skin surface by forming drips--the seat drips off instead of staying near the skin to conduct heat away. 3) Sweating allowed hominids to run and do other heavy work in the heat of the day (since hominids were in fact DIURNAL, day living mammals). Humans can literally run many other mammals to death, through heat exhaustion. Sweating as a temperature regulator also had the effect of making hominids THIRSTY, and more dependant on nearby water sources. C). Extremely thick skull . This seems likely to indicate more need for brain protection from violent assault. What could be the cause? Predators, or other humans. Perhaps
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fighting with clubs between males becomes common in H. erectus as it is in many other modern human societies. D) Small openings in spinal column
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This note was uploaded on 03/01/2011 for the course ASB 194 taught by Professor Hill during the Spring '11 term at ASU.

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ASB 194 lect14.doc - Lect14 Later Evolution of Homo Homo...

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