• Human brain size decrease

    From Pandora@21:1/5 to All on Wed Oct 27 18:54:07 2021
    When and Why Did Human Brains Decrease in Size? A New Change-Point
    Analysis and Insights From Brain Evolution in Ants.

    Abstract

    Human brain size nearly quadrupled in the six million years since Homo
    last shared a common ancestor with chimpanzees, but human brains are
    thought to have decreased in volume since the end of the last Ice Age.
    The timing and reason for this decrease is enigmatic. Here we use
    change-point analysis to estimate the timing of changes in the rate of
    hominin brain evolution. We find that hominin brains experienced
    positive rate changes at 2.1 and 1.5 million years ago, coincident
    with the early evolution of Homo and technological innovations evident
    in the archeological record. But we also find that human brain size
    reduction was surprisingly recent, occurring in the last 3,000 years.
    Our dating does not support hypotheses concerning brain size reduction
    as a by-product of body size reduction, a result of a shift to an
    agricultural diet, or a consequence of self-domestication. We suggest
    our analysis supports the hypothesis that the recent decrease in brain
    size may instead result from the externalization of knowledge and
    advantages of group-level decision-making due in part to the advent of
    social systems of distributed cognition and the storage and sharing of information. Humans live in social groups in which multiple brains
    contribute to the emergence of collective intelligence. Although
    difficult to study in the deep history of Homo, the impacts of group
    size, social organization, collective intelligence and other potential selective forces on brain evolution can be elucidated using ants as
    models. The remarkable ecological diversity of ants and their species
    richness encompasses forms convergent in aspects of human sociality,
    including large group size, agrarian life histories, division of
    labor, and collective cognition. Ants provide a wide range of social
    systems to generate and test hypotheses concerning brain size
    enlargement or reduction and aid in interpreting patterns of brain
    evolution identified in humans. Although humans and ants represent
    very different routes in social and cognitive evolution, the insights
    ants offer can broadly inform us of the selective forces that
    influence brain size.

    Open access:
    https://www.frontiersin.org/articles/10.3389/fevo.2021.742639/full

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  • From littoral.homo@gmail.com@21:1/5 to All on Wed Oct 27 11:42:15 2021
    Thanks, see my comment there.

    Op woensdag 27 oktober 2021 om 18:54:09 UTC+2 schreef Pandora:
    When and Why Did Human Brains Decrease in Size? A New Change-Point
    Analysis and Insights From Brain Evolution in Ants.
    Human brain size nearly quadrupled in the six million years since Homo
    last shared a common ancestor with chimpanzees, but human brains are
    thought to have decreased in volume since the end of the last Ice Age.
    The timing and reason for this decrease is enigmatic. Here we use change-point analysis to estimate the timing of changes in the rate of hominin brain evolution. We find that hominin brains experienced
    positive rate changes at 2.1 and 1.5 million years ago, coincident
    with the early evolution of Homo and technological innovations evident
    in the archeological record. But we also find that human brain size
    reduction was surprisingly recent, occurring in the last 3,000 years.
    Our dating does not support hypotheses concerning brain size reduction
    as a by-product of body size reduction, a result of a shift to an agricultural diet, or a consequence of self-domestication. We suggest
    our analysis supports the hypothesis that the recent decrease in brain
    size may instead result from the externalization of knowledge and
    advantages of group-level decision-making due in part to the advent of
    social systems of distributed cognition and the storage and sharing of information. Humans live in social groups in which multiple brains
    contribute to the emergence of collective intelligence. Although
    difficult to study in the deep history of Homo, the impacts of group
    size, social organization, collective intelligence and other potential selective forces on brain evolution can be elucidated using ants as
    models. The remarkable ecological diversity of ants and their species richness encompasses forms convergent in aspects of human sociality, including large group size, agrarian life histories, division of
    labor, and collective cognition. Ants provide a wide range of social
    systems to generate and test hypotheses concerning brain size
    enlargement or reduction and aid in interpreting patterns of brain
    evolution identified in humans. Although humans and ants represent
    very different routes in social and cognitive evolution, the insights
    ants offer can broadly inform us of the selective forces that
    influence brain size. https://www.frontiersin.org/articles/10.3389/fevo.2021.742639/full

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  • From DD'eDeN aka note/nickname/alas_my_l@21:1/5 to Pandora on Wed Oct 27 12:49:38 2021
    On Wednesday, October 27, 2021 at 12:54:09 PM UTC-4, Pandora wrote:
    When and Why Did Human Brains Decrease in Size? A New Change-Point
    Analysis and Insights From Brain Evolution in Ants.

    Abstract

    Human brain size nearly quadrupled in the six million years since Homo
    last shared a common ancestor with chimpanzees, but human brains are
    thought to have decreased in volume since the end of the last Ice Age.
    The timing and reason for this decrease is enigmatic. Here we use change-point analysis to estimate the timing of changes in the rate of hominin brain evolution. We find that hominin brains experienced
    positive rate changes at 2.1 and 1.5 million years ago, coincident
    with the early evolution of Homo and technological innovations evident
    in the archeological record. But we also find that human brain size
    reduction was surprisingly recent, occurring in the last 3,000 years.
    Our dating does not support hypotheses concerning brain size reduction
    as a by-product of body size reduction, a result of a shift to an agricultural diet, or a consequence of self-domestication. We suggest
    our analysis supports the hypothesis that the recent decrease in brain
    size may instead result from the externalization of knowledge and
    advantages of group-level decision-making due in part to the advent of
    social systems of distributed cognition and the storage and sharing of information. Humans live in social groups in which multiple brains
    contribute to the emergence of collective intelligence. Although
    difficult to study in the deep history of Homo, the impacts of group
    size, social organization, collective intelligence and other potential selective forces on brain evolution can be elucidated using ants as
    models. The remarkable ecological diversity of ants and their species richness encompasses forms convergent in aspects of human sociality, including large group size, agrarian life histories, division of
    labor, and collective cognition. Ants provide a wide range of social
    systems to generate and test hypotheses concerning brain size
    enlargement or reduction and aid in interpreting patterns of brain
    evolution identified in humans. Although humans and ants represent
    very different routes in social and cognitive evolution, the insights
    ants offer can broadly inform us of the selective forces that
    influence brain size.

    Open access: https://www.frontiersin.org/articles/10.3389/fevo.2021.742639/full
    Thanks Pandora, interesting comparison.

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  • From Paul Crowley@21:1/5 to Pandora on Thu Oct 28 13:15:12 2021
    On Wednesday, October 27, 2021 at 5:54:09 PM UTC+1, Pandora wrote:

    When and Why Did Human Brains Decrease in Size? A New Change-Point
    Analysis and Insights From Brain Evolution in Ants.

    https://www.frontiersin.org/articles/10.3389/fevo.2021.742639/full

    Although humans and ants represent very different routes in
    social and cognitive evolution, the insights ants offer can broadly
    inform us of the selective forces that influence brain size.

    An entry for the Ig Nobels?

    An explanation based on simple mechanics will
    always be more parsimonious.

    Take a look at human ancestral hair: i.e. that of
    peoples native to tropics. Firstly, it is costly. It
    would not be present if it wasn't needed. So
    what's the need? It's not protection against
    heat -- humans can usually find shade during the
    day, and no other tropical species have anything
    like it. Nor is there substantial evidence that
    humans are (or ever have been) selected against
    as the result of exposure to heat.

    But humans who have to go into cold waters to
    fish, or travel across dangerous water channels
    do drown. Often hypothermia, affecting the
    brain, is the cause or a major contributory
    factor. Insulation that can reduce the incidence
    will be selected for.

    That brain insulation takes two forms: larger
    brains, and dense, extensive head hair.

    When the pressure of that selection eases, as
    when the bulk of the population ceases to fish in
    cold waters, or travels less (or with less risk) over
    such waters, or stops living on coasts exposed to
    occasional tsunamis, selective pressures will
    decline and the substantial costs involved will
    ensure that brain size declines.

    We can see this in most human populations over
    the last few thousand years. This conclusion is
    reinforced by the example of h.naledi -- a
    population we can assume was never close to
    the sea, and rarely exposed to the night cold
    outside its caves.

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  • From DD'eDeN aka note/nickname/alas_my_l@21:1/5 to Paul Crowley on Fri Oct 29 06:42:31 2021
    On Thursday, October 28, 2021 at 4:15:13 PM UTC-4, Paul Crowley wrote:
    On Wednesday, October 27, 2021 at 5:54:09 PM UTC+1, Pandora wrote:

    When and Why Did Human Brains Decrease in Size? A New Change-Point
    Analysis and Insights From Brain Evolution in Ants. https://www.frontiersin.org/articles/10.3389/fevo.2021.742639/full
    Although humans and ants represent very different routes in
    social and cognitive evolution, the insights ants offer can broadly
    inform us of the selective forces that influence brain size.
    An entry for the Ig Nobels?
    No, just a discourse three levels above your mental acuity.

    An explanation based on simple mechanics will
    always be more parsimonious.
    You confuse effects of social organization with effects of biological organization.

    Take a look at human ancestral hair: i.e. that of
    peoples native to tropics.

    People of tropical ancestry have tightly coiled hair, selected for sun-shading scalp while allowing ventilation superior to straight hair, especially advantageous in hot humid climate.
    People of temperate ancestry have straight or slightly wavy non-coiled hair, selected for thermal insulative qualities, similar to other primates and neanderthals.

    Firstly, it is costly.

    No more than in any other mammal.

    It
    would not be present if it wasn't needed.

    Also true of earlobes. So?

    So
    what's the need? It's not protection against
    heat -- humans can usually find shade during the
    day, and no other tropical species have anything
    like it. Nor is there substantial evidence that
    humans are (or ever have been) selected against
    as the result of exposure to heat.

    See my explanation for tightly coiled hair above.

    Or go on a epic journey to Fantasy Island. Your choice.

    But humans who have to go into cold waters to
    fish, or travel across dangerous water channels
    do drown. Often hypothermia, affecting the
    brain, is the cause or a major contributory
    factor. Insulation that can reduce the incidence
    will be selected for.

    That brain insulation takes two forms: larger
    brains, and dense, extensive head hair.

    When the pressure of that selection eases, as
    when the bulk of the population ceases to fish in
    cold waters, or travels less (or with less risk) over
    such waters, or stops living on coasts exposed to
    occasional tsunamis, selective pressures will
    decline and the substantial costs involved will
    ensure that brain size declines.

    We can see this in most human populations over
    the last few thousand years. This conclusion is
    reinforced by the example of h.naledi -- a
    population we can assume was never close to
    the sea, and rarely exposed to the night cold
    outside its caves.

    Mermaid Follies.

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