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Thread: The origin of the evolution of primates

  1. #1 The origin of the evolution of primates 
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    Please forgive the fact that my questions are laced with known ignorance. I just hope to learn with respect to my curiosities.


    It's come to light recently that the primate fossil record would tend to indicate a journey to, and subsequent diversity within, Africa. This being as opposed to the notion that the primates originated within Africa itself.

    My question is simple. What is the earliest known primate fossil record found within Asia, or anywhere for that matter, other than Africa?


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    Your question really isn't as simple as you might first think. The earliest primates, arguably, would include plesiadapiforms, of which there are about sixteen recognized genera that lived as far back as the late Cretaceous at around 65.5 million years ago (Ma.) and ranged the North American/Eurasian continent (they were connected then) and the South American.

    Plesidapiforms
    They were relatively small, by modern primate standards, their sizes ranging from that of modern shrews to house cats. They're linked to the primate line in a few distinct ways, such as molar and premolar morphology and possibly an early version of the characteristic petrosal bulla (the middle ear) found in later primates.

    Most paleoanthropologists seem to agree (though there is some healthy disagreement that fuels research, which is good) that these plesiadapiforms evolved separately from the line that led to primates of modern aspect. The characteristics that give them similarity, therefore, would have evolved parallel to other primates (through convergence or homoplasy), but this is really hard to detect in fossils going back millions of years (which is why there exists some healthy debate).

    Adapiforms & Omomyiforms
    Most paleoanthropologists and paleontologists, however, agree that primates of modern aspect evolved from a "euprimate" stock. The first radiation of plesiadapiforms (insectivores that had claws but a couple primate-like adaptations in teeth and possibly the middle ear) lasted from the late Cretaceous to about the end of the Eocene. The second radiation, however, also began in the late Cretaceous but the lineages didn't die out. These were the Omomyiforms and the Adapiforms (not to be confused with plesiadapiforms) and they had many derived primate characters which are evident in the fossil record. They had a petrosal bulla, a post-orbital bar, orbital convergence (their eyes were more binocular), grasping hands and feet, and nails instead of claws on each digit.

    They existed throughout the North American/Eurasian continents as well as Africa throughout the same time. The oldest of these is Tetonius, found in 1881 by Jacob Wortman in North America. Tetonius was a tarsier-like primate with a full complement of premolars and small, vertically emplaced incisors (contrasted with the large, procumbant incisors of plesiadapiforms). Tetonius also had a shorter snout and more orbital convergence than either the Adapiforms or the plesiadapiforms (Tetonius was an Omomyiform).

    Anthropoids
    The Omomyiforms are probably closer to anthropoid ancestry, and I've even read some texts that include Tetonius as an anthropoid. This is important because
    the anthropoid line is most clearly ancestral to humans and other modern primates (though many would argue, for good reason, that the lemurs and lorises are direct descendants of euprimates (Adapid and Omomyids).

    The oldest known, indisputable anthropoids are probably represented by teeth found in Algeria which date to 50-46 Ma and by mandibles found in China, Burma and Thailand dating to between 45 and 40 Ma. By strict comparisons of dates, the African samples are older by 5 million years, but the specimens are small and there's a lot of room for evolution to have its way. The oldest known skull, which exhibits postorbital closure (a characteristic of anthropoids) dates to the Fayum Depression of norther Egypt at about 35-34 Ma. From there, most of the variation and diversity among anthropoids occurs in Africa, though there is much going on outside of Africa as well.

    Texts you might find helpful are:

    Klein, Richard G. (2009) The Human Career: human biological and cultural origins. Chicago: University of Chicago Press.

    Beard, Chris K. (2004) The Hunt for the Dawn Monkey. Los Angeles: University of California Press.

    Hartwig, Walter C., ed. (2002). The Primate Fossil Record. Cambridge: University of Cambridge Press.


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    Talk about an abundance of information in one post! An incredible response for which I thank you greatly.

    Do you tend to agree that it was a journey *to* Africa for the primate? From elsewhere that is.

    A long ways off: Not having a real clue what triggers evolution, possibly the move to the intense heat and conditions of the mid to lower African climate is what eventually motivated some of the specialized Simian characteristics as the primate's evolution progressed.
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    Forum Cosmic Wizard SkinWalker's Avatar
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    Quote Originally Posted by Nulledge
    Talk about an abundance of information in one post! An incredible response for which I thank you greatly.
    Thanks. Obviously there is much, much more to it all, so I recommend the resources I listed.

    Do you tend to agree that it was a journey *to* Africa for the primate? From elsewhere that is.
    Not really. It's just as likely that the first primates evolved there as anywhere else. Certainly the most significant primate finds of the Eocene and Miocene were largely in Africa (though there were many significant finds outside).

    There is definitely a lot of evidence for radiation of primate characters in and out of Africa and Eurasia, but its difficult to pin down origins.

    A long ways off: Not having a real clue what triggers evolution, possibly the move to the intense heat and conditions of the mid to lower African climate is what eventually motivated some of the specialized Simian characteristics as the primate's evolution progressed.
    There are a several evolutionary mechanisms that are probably at play. Mostly, though, I suspect the main forcing mechanisms are related to competitive releases and adaptive radiations as climates change and species die off or become extinct, etc. In some cases, certain primate characters allow early primates to out-perform their non-primate competitors. Characters like orbital convergence that allows for binocular vision, polychromatic vision, nails instead of claws, arboreal locomotion, dentition changes, grasping hands and feet, etc.
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    please can anyone provide me notes of the origin of the evolution of primates...thanks.
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    Quote Originally Posted by annie89
    please can anyone provide me notes of the origin of the evolution of primates...thanks.
    The Early Primates, a sub-section of Early Primate Evolution.

    The Origin of Primates

    Primates, from the Tree of Life web project.

    Course notes from the University of New Hampshire

    The Evolution of Primates

    etc.
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