Theories or models on the rate of speciation a Gradualism change is slow and gradual enough change accumulates we call something a new species What sort of fossil evidence would you expect Fossil evidence transitional forms showing gradual change b Punctuated equilibrium A species has a long period of equilibrium little to no change punctuated by a burst of change into a new species Perhaps through the mechanism of macromutation a mutation with far reaching results What sort of fossil evidence expected Fossil evidence Forms show no to very little change for long period of time then sudden change Gradualism versus Punctuated Equilibrium are not mutually exclusive we believe we see both in the fossil record What examples have we seen in the fossil record for human evolution Punctuated equilibrium Bipedalism First H erectus Within H erectus equilibrium Gradualism Archaic Homo sapiens transitional between H erectus and H sapiens Also transitional anatomically modern H sapiens By 28 00 ya ALL humans are anatomically modern H sapiens with the exception of one island It is these people who colonize the remaining areas of the world e g America Australia Siberia We ll talk about this colonization next week So called Hobbits Homo floresiensis Found in 2004 on island of Flores in Indonesia three foot high brain 1 3 size of ours Peter Brown in archaeology about com Wong 2009 Controversial interpretations New species Homo sapiens with microcephaly Diseased for ex cretinism Laron syndrome We ll agree it is a new species Apparently evolved into small size as a response to the limited resources on an island Something we ve seen in other mammals but never before in humans Recovered from deep deposits in a limestone cave Wong 2009 Found 100 000 17 000 ya well dated by C14 and other dating techniques Thought to have arrived as full size Homo erectus 1 mya that s when H erectus appear on island Evolutionary dwarfism not uncommon for large mammals that arrive on an island to quickly shrink in size including 30 shrinkage of brain Found associated with animal bones and stone tools Hunted pygmy elephants and other game fish Tool kit is very basic similar to H habilis tool kit Wong 2009 So far recovered bones from 14 individuals Recent analyses late 2009 raise more questions Finding some primitive features that are puzzling Foot big toe is aligned like ours BUT is short other toes long curved and foot lacks an arch all ape like characteristics Also foot is unusually long Short leg bones long feet Wong 2009 http humanorigins si edu resources multimedia videos hobbits flores indonesia In fact below the head they look more like Australopithecus Lucy than Homo BUT Even though brain is grapefruit sized 417 cu cm The head looks like Homo narrow nose prominent arches over each eye Newest explanations say it did not evolve from H erectus but either from H habilis or even before H habilis What s so controversial about saying it evolved with from H habilis That means that H habilis left Africa pushing the radiation out of Africa back in time Also difficult to understand it existed until fairly recently only 17 000 ya May have had contact with anatomically modern Homo sapiens there based on continuity of stone tool styles Wong 2009 To conclude about the hobbits we are still somewhat mystified about what species these represent when they arrived or when they developed and how they could have persisted until so recently 17 000 ya
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