• First hominin muscle reconstruction show

    From ScienceDaily@1:317/3 to All on Wed Jun 14 22:30:34 2023
    First hominin muscle reconstruction shows 3.2 million-year-old 'Lucy'
    could stand as erect as we can

    Date:
    June 14, 2023
    Source:
    University of Cambridge
    Summary:
    Digital modelling of legendary fossil's soft tissue suggests
    Australopithecus afarensis had powerful leg and pelvic muscles
    suited to tree dwelling, but knee muscles that allowed fully
    erect walking.


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    FULL STORY ==========================================================================
    A Cambridge University researcher has digitally reconstructed the missing
    soft tissue of an early human ancestor -- or hominin -- for the first
    time, revealing a capability to stand as erect as we do today.

    Dr Ashleigh Wiseman has 3D-modelled the leg and pelvis muscles of the
    hominin Australopithecus afarensisusing scans of 'Lucy': the famous
    fossil specimen discovered in Ethiopia in the mid-1970s.

    Australopithecus afarensis was an early human species that lived in East
    Africa over three million years ago. Shorter than us, with an ape-like
    face and smaller brain, but able to walk on two legs, it adapted to both
    tree and savannah dwelling -- helping the species survive for almost a
    million years.

    Named for the Beatles classic 'Lucy in the Sky with Diamonds', Lucy
    is one of the most complete examples to be unearthed of any type of Australopithecus - - with 40% of her skeleton recovered.

    Wiseman was able to use recently published open source data on the Lucy
    fossil to create a digital model of the 3.2 million-year-old hominin's
    lower body muscle structure. The study is published in the journal Royal Society Open Science.

    The research recreated 36 muscles in each leg, most of which were
    much larger in Lucy and occupied greater space in the legs compared to
    modern humans.

    For example, major muscles in Lucy's calves and thighs were over twice
    the size of those in modern humans, as we have a much higher fat to
    muscle ratio.

    Muscles made up 74% of the total mass in Lucy's thigh, compared to just
    50% in humans.

    Paleoanthropologists agree that Lucy was bipedal, but disagree on how she walked. Some have argued that she moved in a crouching waddle, similar to chimpanzees -- our common ancestor -- when they walk on two legs. Others believe that her movement was closer to our own upright bipedalism.

    Research in the last 20 years have seen a consensus begin to emerge
    for fully erect walking, and Wiseman's work adds further weight to
    this. Lucy's knee extensor muscles, and the leverage they would allow,
    confirm an ability to straighten the knee joints as much as a healthy
    person can today.

    "Lucy's ability to walk upright can only be known by reconstructing the
    path and space that a muscle occupies within the body," said Wiseman, from Cambridge University's McDonald Institute for Archaeological Research.

    "We are now the only animal that can stand upright with straight
    knees. Lucy's muscles suggest that she was as proficient at bipedalism
    as we are, while possibly also being at home in the trees. Lucy likely
    walked and moved in a way that we do not see in any living species today," Wiseman said.

    "Australopithecus afarensis would have roamed areas of open wooded
    grassland as well as more dense forests in East Africa around 3 to 4
    million years ago.

    These reconstructions of Lucy's muscles suggest that she would have been
    able to exploit both habitats effectively." Lucy was a young adult,
    who stood at just over one metre tall and probably weighed around
    28kg. Lucy's brain would have been roughly a third of the size of ours.

    To recreate the muscles of this hominin, Wiseman started with some living humans. Using MRI and CT scans of the muscle and bone structures of a
    modern woman and man, she was able to map the "muscle paths" and build
    a digital musculoskeletal model.

    Wiseman then used existing virtual models of Lucy's skeleton to
    "rearticulate" the joints -- that is, put the skeleton back together. This
    work defined the axis from which each joint was able to move and rotate, replicating how they moved during life.

    Finally, muscles were layered on top, based on pathways from modern human muscle maps, as well as what little "muscle scarring" was discernible (the traces of muscle connection detectable on the fossilised bones). "Without
    open access science, this research would not have been possible,"
    said Wiseman.

    These reconstructions can now help scientists understand how this human ancestor walked. "Muscle reconstructions have already been used to gauge running speeds of a T-Rex, for example," said Wiseman. "By applying
    similar techniques to ancestral humans, we want to reveal the spectrum
    of physical movement that propelled our evolution -- including those capabilities we have lost."
    * RELATED_TOPICS
    o Fossils_&_Ruins
    # Early_Humans # Fossils # Human_Evolution # Anthropology
    # Origin_of_Life # Cultures # Evolution # Archaeology
    * RELATED_TERMS
    o Fossil o Petrified_wood o Evolution_of_cetaceans o
    Homo_rudolfensis o Trace_fossil o Paralititan o Tyrannosaurus
    o Evolution

    ========================================================================== Story Source: Materials provided by University_of_Cambridge. The original
    text of this story is licensed under a Creative_Commons_License. Note:
    Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Ashleigh L. A. Wiseman. Three-dimensional volumetric muscle
    reconstruction of the Australopithecus afarensis pelvis and limb,
    with estimations of limb leverage. Royal Society Open Science,
    2023; 10 (6) DOI: 10.1098/rsos.230356 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2023/06/230614220724.htm

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