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View Diary: How Homo sapiens Populated the Earth: Part Two (19 comments)

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  •  As to language and cognitive function, (3+ / 0-)
    Recommended by:
    Pluto, blueoasis, Aunt Pat

    allow me to point out some recent developments in neuroscience, which, to my mind, greatly change the debate over these issue in the fossil record.

    a) Neural spindles. I'll unpack this for other readers, as you may be well aware of them.

    These are very long neurons with few dendrites at either end. They serve as an express lane, if you will, allowing a signal to move between regions of the brain more directly and more reliably.

    They are present in many social mammals -- elephants, whales and dolphins, and great apes. Oh, and us.

    If a neural spindle is severed, the result is a diminution in language skill, intelligence, and social awareness/ social skills. It follows, then, that they are central to all those functions.

    b) The human glial cells. These helper cells attached to the neurons are quite different in their human form, being individually more complex and more densely distributed than those of other species.

    They also have been found to signal other glials, both on the same neuron and on other neurons, especially near the dendrites. This amplifies tremendously the 'bandwidth' if you will of inter-neural communication.

    A recent experiment injected human glia into mice, with a significant increase in memory, communicativity, and problem solving ability resulting.

    c) The addition of human glia to spindle cells is sufficient to explain, then, the enhanced linguistic ability, sociality, and overall intelligence of H. sapiens.

    To date, I don't believe that this last glial mutation has been dated. When it is, we'll know a good deal more about the abilities of our ancestors, sapiens and otherwise. We may even find that it dates to the technological diversification which occurred between 80k and 50k ybp.

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