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Thread: "Big Brain" Gene Allowed for Evolutionary Expansion of Our Neocortex

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    tWebber shunyadragon's Avatar
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    "Big Brain" Gene Allowed for Evolutionary Expansion of Our Neocortex

    Source: http://www.scientificamerican.com/article/big-brain-gene-allowed-for-evolutionary-expansion-of-our-neocortex/?WT.mc_id=SA_DD_20150227



    "Big Brain" Gene Allowed for Evolutionary Expansion of Our Neocortex

    A single gene may have paved the way for the rise of human intelligence by dramatically increasing the number of brain cells found in a key brain region.

    This gene seems to be uniquely human: It is found in modern-day humans, Neanderthals and another branch of extinct humans called Denisovans, but not in chimpanzees.

    By allowing the brain region called the neocortex to contain many more neurons, the tiny snippet of DNA may have laid the foundation for the human brain's massive expansion.

    "It is so cool that one tiny gene alone may suffice to affect the phenotype of the stem cells, which contributed the most to the expansion of the neocortex," said study lead author Marta Florio, a doctoral candidate in molecular and cellular biology and genetics at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany. Still, it's likely this gene is just one of many genetic changes that make human cognition special, Florio said.

    An expanding brain

    The evolution from primitive apes to humans with complex language and culture has taken millions of years. Some 3.8 million ago, Australopithecus afarensis, the species typified by the iconic early human ancestor fossil Lucy, had a brain that was less than 30 cubic inches (500 cubic centimeters) in volume, or about a third the size of the modern human brain. By about 1.8 million years ago, Homo erectus was equipped with a brain that was roughly twice as big as that of Australopithecus. H. erectus also showed evidence of tool and fire use and more complex social groups.

    Once anatomically modern humans, and their lost cousins the Neanderthals and Denisovans, arrived on the scene, the brain had expanded to roughly 85 cubic inches (1.4 liters) in volume. Most of this growth occurred in a brain region called the neocortex.

    "The neocortex is so interesting because that's the seat of cognitive abilities, which, in a way, make us human — like language and logical thinking," Florio told Live Science.

    The neocortex is so large because it is jam-packed with neurons, or brain cells. But what genetic changes ushered in this explosion of neurons?

    Single gene

    To understand that question, Florio, along with her thesis advisor, Dr. Wieland Huttner, a neurobiologist also at the Max Planck Institute, were studying one type of neural progenitor cell, a stem cell that divides and then forms brain cells during embryonic development. In mice, these cells divide once, and then make neurons. But in humans, these same types of cells divide many times over before forming a huge number of neurons.

    Florio isolated this pool of cells, and then analyzed the genes that were turned on in both mice and humans at a stage of peak brain development. (The researchers looked at this process in both 13-week gestation human fetuses whose tissue had been donated by women after abortions and in mice at 14 days gestation.)

    The researchers found that a particular gene, called ARHGAP11B, was turned on and highly activated in the human neural progenitor cells, but wasn't present at all in mouse cells. This tiny snippet of DNA, just 804 letters, or bases, long, was once part of a much longer gene, but somehow this fragment was duplicated and the duplicated fragment was inserted into the human genome.

    Then the team inserted and expressed (turned on) this DNA snippet in the brains of mice. Though mice normally have a tiny, smooth neocortex, the mice with the gene insertion grew what looked like larger neocortices; these amped-up brain regions contained loads of neurons and some even began forming the characteristic folds, or convolutions, found in the human brain, a geometry that packs a lot of dense brain tissue into a small amount of space. (The researchers did not check to see if the mice actually got smarter, though that is a potential avenue of future research, Florio said).

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    tWebber 37818's Avatar
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    Mice are really pan dimensional beings . . .





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    tWebber Yttrium's Avatar
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    The next step is to plant this gene into various types of apes and see what happens. What could possibly go wrong?
    Middle-of-the-road swing voter. Feel free to sway my opinion.

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    Professor Cerebrum123's Avatar
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    Quote Originally Posted by Yttrium View Post
    The next step is to plant this gene into various types of apes and see what happens. What could possibly go wrong?



    Last edited by Cerebrum123; 03-31-2015 at 01:27 PM.

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    tWebber 37818's Avatar
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    . . . the Gospel of Christ, for it is [the] power of God to salvation to every [one] believing, . . . -- Romans 1:16.

    . . . that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures: . . . -- 1 Corinthians 15:3, 4.

    Whosoever believeth that Jesus is the Christ is born of God: . . . -- 1 John 5:1.

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    tWebber Yttrium's Avatar
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    Quote Originally Posted by 37818 View Post
    This newer finding seems to dispel an earlier theory as to why humans have the bigger brain.
    Or perhaps we benefited from the combination of the two.
    Middle-of-the-road swing voter. Feel free to sway my opinion.

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    tWebber 37818's Avatar
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    Quote Originally Posted by Yttrium View Post
    Or perhaps we benefited from the combination of the two.
    Most likely so. There is really no presented evidence one instruction set caused the other instruction set.
    . . . the Gospel of Christ, for it is [the] power of God to salvation to every [one] believing, . . . -- Romans 1:16.

    . . . that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures: . . . -- 1 Corinthians 15:3, 4.

    Whosoever believeth that Jesus is the Christ is born of God: . . . -- 1 John 5:1.

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