The closest living relatives of man are apes such as chimpanzees, gorillas, orangutans, and gibbons. We all had the same common ancestor who lived during the Miocene era (23 million to 5 million years ago). While scientists don’t have any remains of this mysterious creature, what would it have looked like?
In other words, what was the size of our last common ancestor (LCA), and what did its skull, brain, legs, arms, and even fingers look like, based on the available evidence?
We don’t have all the answers. But its closest equivalents alive today may be gorillas and chimpanzees.
One big unknown is the size of the LCA Christopher GilbertA paleontologist at City University of New York’s Hunter College told Live Science. This is because of the monkey Fossils from the period during which the LCA lived are rarenoted a 2017 study in the journal Nature.
Early or “stem” apes span a wide range of body sizes, from small-sized species to larger primates approaching the size of a gorilla, making it difficult to determine the weight of the LCA without a better understanding of the evolutionary relationships and history, said Gilbert, who co-authored the Nature study. , these types.
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Swinging from trees or walking?
Current evidence indicates that the LCA was most likely a four-legged animal. Fossils indicate that stem apes were able to climb vertically and had a suspenseful behaviour, just as modern humans can use their arms to hang from tree branches. However, unlike all viviparous apes, which prefer to live hanging below or among tree branches, at least some stem apes were not specialized in hanging behaviour, lacking adaptations such as long and highly curved fingers and toes, and highly mobile wrists, shoulders and hips. joints. Gilbert said that meant LCA probably wasn’t a suspension specialist, either.
Some researchers have sometimes speculated “that the LCA may have been bipedal,” moving on two legs like a human, Thomas Cody PrangThe human paleontologist at Washington University in St. Louis told Live Science. However, since “LCA was a quadruped, like other primates,” it likely did not walk on two legs but rather used all fours.
Head, shoulders, knees and toes
Stem apes displayed a range of head shapes. Some had skulls like gibbons with short faces while others had longer faces resembling primitive monkeys and Old World monkeys, such as baboons (genus Papio) and macaques (genus macaca), Gilbert said. “We still know for sure that the LCA’s brain size was smaller than that of a human,” Prang said. Since it was a quadruped, the head would not have sat on top of the body as a bipedal man would, but would have been positioned more forward like a gorilla or a chimpanzee.
The arms and legs of early apes are often not well preserved in the fossil record. Still, “the upper limbs of early hominins [humans and our close relatives and ancestors] They appear large and heavily built, which is associated with forelimbs-dominated locomotion—that is, climbing and hanging.”Gorilla Gorilla And Beringei gorilla(chimpanzee)Pan Caves), orangutans (genus Bongo) and bonobo (pan baniscus) – of humans, note. In essence, early hominins appear to have been built for tree canopies, not open savannas.
On the one hand, in a 2021 study in the journal Science advancesanalyzed by Prang and colleagues ArdipithecusThe 4.4-million-year-old hand found “was most similar to chimpanzees and bonobos among all living humans, apes, and apes.” This, in turn, may indicate that the LCA had long, curved finger bones.
Humans, chimpanzees, gorillas, and bonobos all walk with heels touching the ground, Prang said, suggesting the LCA did the same.
This form of locomotion is often associated with other traits seen in living African apes—gorillas, chimpanzees, and bonobos—such as the use of joints to aid walking and evolutionary adaptations for vertical climbing. “All the traits that we can reasonably study indicate that early hominins, and thus likely the LCA, distinguished these same components of this adaptive package,” Prang said. “The LCA was neither a gorilla nor a chimpanzee, but it was most likely the most similar to gorillas and chimpanzees among all known primates.”
The LCA’s appearance “remains quite controversial,” Gilbert said. Filling out the picture will require new fossil finds.
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