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4_2 Trends in Primate Evolution_Lecture Script.pdf

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ARCH 131
Dennis Sandgathe

UNIT 4PRIMATES 42 Trends in Primate Evolution Slide 1 Title slide Slide 2 Although for this course we are mainly interested in the emergence of humans this was simply the end of a long process that included some important and consistent trends We humans and our immediate hominin ancestors have many characteristics that began to emerge many millions of years ago among our distant primate ancestors Its important to have some understanding of the bigger picture of primate evolution Slide 3 However before we continue there are a few more important terms dealing with longterm evolutionary processes that we need to know Adaptive Radiation is the relatively rapid process of speciation resulting from a species moving to fill new or different ecological niches Adaptive Radiation events usually follow a major change in the environmentalmajor climate change for example which makes new regions available to species that previously wouldnt survive thereOver the last 10 million years there have been a number of migrations of animals moving between North America and Asia or between Eurasia and Africa When these migrating animals entered these new regions they often underwent significant evolutionary changes to fit the new environmental circumstances they encountered Slide 4 Divergent Evolution is seen as the typical course of natural selection in which related species adapting to different ecological niches slowly diverge from each other in form There are many examples among living animals of divergent evolution These two species of fox are one but think of all the different species of deer in the world and different species of bears or cats These are all examples of divergent evolution Slide 5 Parallel Evolution seems to be less common than divergent evolution but there are still many examples of it Parallel Evolution is the independent evolution of similar traits in different species but starting from a similar but very distant ancestor European and North American wolves and the now extinct Tasmanian wolf are good examples Although the Tasmanian wolf was a mammal and therefore obviously related to this European wolf the Tasmanian wolf was a marsupial and so must be only very distantly related Slide 6 Convergent Evolution involves much longer periods of time but is a more dramatic process Different species which have very different ancestral lines evolve similar adaptations There are some classic examples of Convergent EvolutionBirds bats and insects have some distant common evolutionary ancestor but it predates the development of flight by 100s of millions of years These three groups represent 3 very distinct evolutionary paths and yet all 3 have independently developed the ability to flyFish and whales are another exampleboth groups evolved to swim using very similar appendages and to live exclusively under water These groups evolutionary connections are also very distantfish having a very ancient line first appearing around 500 million years ago and whales evolving much more recently around 50 million years ago from a wolflike ancestor
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