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a201-11f-20-FirstPrimates - Introduction to Biological...

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Introduction to Biological Anthropology: Notes 20 Paleontology and the first primates Copyright Bruce Owen 2010 - So far, we have seen how evolution works in general, and how it has shaped our closest relatives, the non-human primates - Now we will shift gears again, and look at the direct evidence of how our own kind evolved - we want to know basically two things - the sequence of steps that led from some kind of animal in the past to modern humans - and the evolutionary reasons for each one of those steps - why would our quadrupedal ancestors evolve into bipeds? - why would they develop language? … etc. - this is still an active field, with many questions left to be resolved - this direct evidence comes from paleontology - the study of fossilized animal and plant remains - for animals, usually bones - occasionally, other body parts and evidence of them - usually, when an animal or plant dies, the bones and other parts rot, weather, and decay away - under some rare circumstances, bones can be preserved as fossils - the most common form of fossil is formed when the organic material gradually dissolves away and is replaced by minerals that crystallize out of ground water - this creates a rock in the exact shape of the bone - which is then very durable, and may last long enough to be found and studied - the study of fossils is paleontology , done by paleontologists - most paleontologists study extinct animals (and plants) that are not primates, as the evolutionary arm of biology - the study of fossils of animals ancestral to humans and our close relatives is a sub-specialty often called paleoanthropology , done by paleoanthropologists - by the way, archaeologists like me do not normally study fossils - we study the material evidence of cultural activity by people - that is, tools, houses, campsites, garbage dumps, burials, etc. - sometimes that includes the remains of human bodies or other animals - this stuff is usually much more recent than any fossils - We can often determine the age of fossils - The book explains briefly how some of these methods work, but we won’t take the time to go through the physics of these methods here - Potassium-argon dating tells us how long ago lava or ash cooled to a solid - but works only on rocks (not the fossils themselves) - and the rocks must have cooled from liquid at least half a million years ago - used by dating a layer of basalt (lava) or ash (frothy lava that was blown out and cooled while airborne) from above the fossil and another from below it, to bracket the fossil’s age - Radiocarbon dating tells us how long ago a living thing died - but works only on organic material that is less than 70,000 to 50,000 years old
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Intro to Biological Anthro F 2011 / Owen: Paleontology and the first primates p. 2 - most of human evolution occurred too long ago for the radiocarbon method to help - and other methods… - The point: we can tell how old fossils are, but with differing degrees of accuracy and precision, depending on the fossil’s age and the conditions where it was buried -
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a201-11f-20-FirstPrimates - Introduction to Biological...

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