Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Theories or models on the rate of speciationa. Gradualism change is slow and gradual enough change accumulates, we call something a new speciesWhat sort of fossil evidence would you expect?Fossil evidence: transitional forms showing gradual changeb. Punctuated equilibriumA species has a long period of equilibrium(little to no change), punctuated by a burst of changeinto a new speciesPerhaps 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 periodof time, then sudden changeGradualism versus Punctuated Equilibriumare not mutually exclusive:we believe we see both in the fossil recordWhat examples have we seenin the fossil record for human evolution?Punctuated equilibrium GradualismBipedalism!First H. erectus?Within H. erectus(equilibrium)Archaic Homo sapiens(transitional betweenH. erectus and H. sapiensAlso transitionalanatomically modernH. sapiensBy 28,00 ya,ALL humans are anatomically modern H. sapiens(with the exception of one island)It is these people who colonize the remaining areasof the world: e.g., America, Australia, SiberiaWe’ll talk about this colonization next weekSo-called Hobbits:Homo floresiensisFound in 2004 on island of Flores in Indonesiathree-foot high, brain 1/3 size of ours(Peter Brown inarchaeology.about.com)(Wong 2009)We’ll agree it is a new speciesApparently evolved into small size as a response to thelimited resources on an island,Something we’ve seen in other mammals, but never before in humansControversial interpretations:New species? Homo sapiens with microcephaly?Diseased? (for ex: cretinism? Laron syndrome?)(Wong 2009)Recovered from deep deposits in a limestone caveFound 100,000-17,000 ya, well dated by C14 and other dating techniquesThought to have arrived as full-size Homo erectus1 mya (that’s when H. erectus appear on island)Evolutionary dwarfism: not uncommon for largemammals that arrive on an island to quicklyshrink in size, including 30% shrinkage of brainFound associated with animal bones and stone toolsHunted pygmy elephants and other game, fishTool kit is very basic, similar to H. habilis tool kit(Wong 2009)So far recovered bones from 14 individualsRecent 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 characteristicsAlso, foot is unusually long!(Wong 2009)Short leg bones,long feethttp://humanorigins.si.edu/resources/multimedia/videos/hobbits-flores-indonesiaIn fact, below the head they look more likeAustralopithecus (Lucy) than HomoBUTEven though brain is grapefruit-sized (417 cu cm),The head looks like Homo: narrow nose, prominent arches over each eyeNewest explanations say it did not evolve fromH. erectus, but either from H. habilis or evenbefore H. habilisWhat’s so controversial about saying itevolved with/from H. habilis?That means that H. habilis left Africa, pushing the radiation out of Africa backin timeAlso difficult to understand: it existed untilfairly recently, only 17,000 ya!May have had contact with anatomicallymodern Homo sapiens there, basedon continuity of stone tool styles!(Wong 2009)To conclude about the “hobbits”:we are still somewhat mystified aboutwhat species these represent,when they arrived or when they developedand how they could have persisted untilso recently (17,000
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