human-evolution

human-evolution - Human evolution. Fascinating subject -...

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Human evolution. Fascinating subject - where did we come from? History of Primates: - evolved from shrews during Cretaceous (so an older order) about 65 mya. - Some characteristics of primates: - clavicle well developed (allows increase flexibility, supports arms). - five digits, front and rear. Often thumb (and big toe) opposable. - claws -> nails - lots of skin receptors in fingers. - snout shortened (sense of smell is less important - Why?). - usually only one pair of mammary glands - excellent vision, well developed nervous control, often increased intelligence. - Several orders and suborders. In general, lemurs, a few smaller groups such as bush babies and tarsiers, old world monkeys, new world monkeys, and “humans & great apes (sometimes gibbons are included with the great apes)” [Fig. 34.37, p. 726] . - Origin of humans [Fig. 34.40, p. 729] : - your text says nothing about most of the species in this figure! - some preliminary remarks. There is a lot of controversy here. Some of it just plain silly (i.e., is species “x” part of the genus “Homo” or the genus “Australopithecus”). - much of it also has to do with which species are thought to be ancestral to humans, and which are not. We'll see some of this. [Note: many of the following figures are not in the text. Most can be found on the web] - a possible common ancestor for both humans and apes (i.e. split from rest of primates): - no way to “prove” this, but might be Proconsul or something like it. Shows many features of both humans and great apes - roughly 18 mya. - On the other hand, a few years ago: - Sahelanthropus tchadensis , or “Toumaë” (meaning “hope of life” in the local language. - discovered in northern Chad. - 6 - 7 million years old. - fairly complete skull. - thought to be a hominid, and therefore possibly our ancestor (far too early to be sure, though). - bipedal? no one is sure.
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- some folks consider this a common ancestor between us and the great apes. - Orrorin tugenensis , from about 6 mya. This is another possible human ancestor, though a bit more recent than Sahelanthropus . - Strangely, there is some evidence that this may be more human than some of the Australopithecus species (generally considered on the line to humans) - found in Kenya - definitely bipedal, and a forest dweller (meaning the origins of
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human-evolution - Human evolution. Fascinating subject -...

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