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Mennesker og træer

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Oprettet: 14 Okt 2007
Sted: Frederiksberg
Status: Offline
Point: 30201
Indlæg funktioner Indlæg funktioner   Tak (0) Tak(0)   Citér Prutterhunden Citér  BesvarSvar Direkte link til dette indlæg Emne: Mennesker og træer
    Sendt: 21 Apr 2021 kl. 15:46
Mennesker - ialtfald nogle af os - har en særlig tilknytning til træer. Det ligger måske i vore gener?

Børn elsker at klatre i træer. Måske ikke så underligt, for det gjorde vore forfædre også, selv efter de skilte sig ud fra de andre aber. For 3.67 millioner år siden var vore skuldre stadig formet for at hænge og klatre i træer, mens vore ben og fødder var "gået foran" og var som vor tids mennesker beregnet til at gå på jorden.

At bruge armene til at kaste med sten, spyd osv. for at jage byttedyr, har altså været en langsommelig proces.

"A long-awaited, high-tech analysis of the upper body of famed fossil 'Little Foot' opens a window to a pivotal period when human ancestors diverged from apes

Although other parts of Little Foot, especially its legs, show humanlike traits for upright walking, the shoulder components are clearly apelike, supporting arms surprisingly well suited for suspending from branches or shimmying up and down trees rather than throwing a projectile or dangling astride the torso like humans.

Little Foot is the Rosetta stone for early human ancestors. When we compare the shoulder assembly with living humans and apes, it shows that Little Foot's shoulder was probably a good model of the shoulder of the common ancestor of humans and other African apes like chimpanzees and gorillas.

The Little Foot fossil is a rare specimen because it's a near-complete skeleton of an Australopithecus (sydabe) individual much older than most other human ancestors. The creature, probably an old female, stood about 4 feet (122 cm) tall with long legs suitable for bipedal motion when it lived some 3.67 million years ago. Called "Little Foot" because the first bones recovered consisted of a few small foot bones, the remains were discovered in a cave in South Africa in the 1990s.

Little Foot provides the oldest and most intact example of this anatomy ever found. In human evolution these parts had to change form before our ancestors could live life free of trees, walk the open savannah and use their arms for functions other than supporting the weight of the individual.

We see incontrovertible evidence in Little Foot that the arm of our ancestors at 3.67 million years ago was still being used to bear substantial weight during arboreal movements in trees for climbing or hanging beneath branches. In fact, based on comparisons with living humans and apes, we propose that the shoulder morphology and function of Little Foot is a good model for that of the common ancestor of humans and chimpanzees 7 million to 8 million years ago.

Little Foot fossil shows early human ancestor clung closely to trees (phys.org)
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