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Our Earliest Ancestor

EnolaGaia said:
The fossil known as 'Toumai' continues to be controversial. A pair of new papers (one published; one under review) debate whether Toumai represents a bipedal human ancestor. ...
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The second of the two research papers mentioned in my 2020 post has now been peer-reviewed and published. As a result, the debate over the status of Sahelanthropus tchadensis in human evolution continues. Analysis of a thigh bone only recently identified as probably from the species suggests S. tchadensis was bipedal.
Our first steps? Fossil may boost case for earliest ancestor

Twenty years ago, scientists discovered a 7-million-year-old skull that they concluded belonged to a creature who walked upright and was our earliest known ancestor. Not everyone was convinced. Now, the researchers are back with more evidence they say strengthens their case.

Their new study published Wednesday analyzed arm and leg fossils found near the skull in Africa, looking for signs of walking on two feet instead of on all fours. When early humans started walking upright, it marked a key moment in our split away from apes

In the paper in the journal Nature, researchers again place the creature just on the human side of that evolutionary divide. The fossil species, named Sahelanthropus tchadensis, walked upright while still being able to climb around in trees, they reported.

The species has been dated to around 7 million years ago, which makes it the oldest known human ancestor, by a long shot. That’s about a million years older than other early known hominins. ...

But it’s been a source of fierce debate since the fossils were first unearthed in Chad in 2001. ...

The latest work includes a thighbone that was not linked to S. tchadensis at first and went unstudied for years. Other researchers at the French university found the bone in the lab’s collection and realized it probably belonged to the fossil species.

Compared to bones from other species, the thighbone matched up better with upright-walking humans than knuckle-walking apes, according to the study. ...

Still, the debate over the species is likely to continue. ...
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FULL STORY: https://apnews.com/article/science-fossils-885a2281be33dd145c3a0cfe86eb54f1
 
Here are the bibliographic details and abstract from the newly published study.

Daver, G., Guy, F., Mackaye, H.T. et al.
Postcranial evidence of late Miocene hominin bipedalism in Chad.
Nature (2022).
https://doi.org/10.1038/s41586-022-04901-z

Abstract
Bipedal locomotion is one of the key adaptations that define the hominin clade. Evidence of bipedalism is known from postcranial remains of late Miocene hominins as early as 6 million years ago (Ma) in eastern Africa1,2,3,4. Bipedality of Sahelanthropus tchadensis was hitherto inferred about 7 Ma in central Africa (Chad) based on cranial evidence5,6,7. Here we present postcranial evidence of the locomotor behaviour of S. tchadensis, with new insights into bipedalism at the early stage of hominin evolutionary history. The original material was discovered at locality TM 266 of the Toros-Ménalla fossiliferous area and consists of one left femur and two, right and left, ulnae. The morphology of the femur is most parsimonious with habitual bipedality, and the ulnae preserve evidence of substantial arboreal behaviour. Taken together, these findings suggest that hominins were already bipeds at around 7 Ma but also suggest that arboreal clambering was probably a significant part of their locomotor repertoire.

SOURCE: https://www.nature.com/articles/s41586-022-04901-z
 
1.8m-year-old tooth of early human found on dig in Georgia.

Student’s find provides new evidence region may be one of first places early humans settled outside Africa.

Archaeologists in Georgia have found a 1.8m-year-old tooth belonging to an early species of human that they say cements the region as the home of one of the earliest prehistoric human settlements in Europe, and possibly anywhere outside Africa.

The tooth was discovered near the village of Orozmani, which lies about 60 miles south-west of the Georgian capital, Tbilisi, and is near Dmanisi, where human skulls dated to 1.8m years old were found in the late 1990s and early 2000s.


The Dmanisi finds were the oldest such discovery anywhere in the world outside Africa, and changed scientists’ understanding of early human evolution and migration patterns.

The latest discovery at a site about 12 miles away away provides yet more evidence that the mountainous south Caucasus area was probably one of the first places early humans settled after migrating out of Africa, experts said.

“Orozmani, together with Dmanisi, represents the centre of the oldest distribution of old humans – or early Homo – in the world outside Africa,” the National Research Centre of Archaeology and Prehistory of Georgia said.
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(C) The guardian. '22.
 
EnolaGaia said:
Here are the bibliographic details and abstract from the newly published study.

Daver, G., Guy, F., Mackaye, H.T. et al.
Postcranial evidence of late Miocene hominin bipedalism in Chad.
Nature (2022).
https://doi.org/10.1038/s41586-022-04901-z

Abstract
Bipedal locomotion is one of the key adaptations that define the hominin clade. Evidence of bipedalism is known from postcranial remains of late Miocene hominins as early as 6 million years ago (Ma) in eastern Africa1,2,3,4. Bipedality of Sahelanthropus tchadensis was hitherto inferred about 7 Ma in central Africa (Chad) based on cranial evidence5,6,7. Here we present postcranial evidence of the locomotor behaviour of S. tchadensis, with new insights into bipedalism at the early stage of hominin evolutionary history. The original material was discovered at locality TM 266 of the Toros-Ménalla fossiliferous area and consists of one left femur and two, right and left, ulnae. The morphology of the femur is most parsimonious with habitual bipedality, and the ulnae preserve evidence of substantial arboreal behaviour. Taken together, these findings suggest that hominins were already bipeds at around 7 Ma but also suggest that arboreal clambering was probably a significant part of their locomotor repertoire.

SOURCE: https://www.nature.com/articles/s41586-022-04901-z
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Another study, observing chimpanzees, offers a theory about bipedalism originating in trees. Does it make a good deal of sense?

Human bipedalism—walking upright on two legs—may have evolved in trees, and not on the ground as previously thought, according to a new study involving UCL researchers.

In the study, published today in the journal Science Advances, researchers from UCL, the University of Kent, and Duke University, U.S., explored the behaviors of wild chimpanzees—our closest living relative—from the Issa Valley of western Tanzania, within the region of the East African Rift Valley.

Known as "savanna-mosaic"—a mix of dry open land with few trees and patches of dense forest—the chimpanzees' habitat is very similar to that of our earliest human ancestors and was chosen to enable the scientists to explore whether the openness of this type of landscape could have encouraged bipedalism in hominins.

The study is the first of its kind to explore if savanna-mosaic habitats would account for increased time spent on the ground by the Issa chimpanzees, and compares their behavior to other studies on their solely forest-dwelling cousins in other parts of Africa.

Overall, the study found that the Issa chimpanzees spent as much time in the trees as other chimpanzees living in dense forests, despite their more open habitat, and were not more terrestrial (land-based) as expected. ...

https://phys.org/news/2022-12-early-humans-upright-trees.html
 
Lucy was no slouch.

Lucy, the world’s most famous early human ancestor, had knee joints that allowed her to walk fully upright as well as strong leg and pelvic muscles suited to living in trees, research suggests.

For the first time, scientists at the University of Cambridge digitally reconstructed the lower limb muscles of the extinct ape-like relative who lived in Africa more than three million years ago.

The results, published in the journal Royal Society Open Science, suggest Lucy could straighten her knee joints, giving her the ability to stand upright and walk on two legs with an erect posture, similar to modern-day humans.

The team also found that her leg muscles were bigger and more powerful than those seen in modern humans, enabling her to live in trees like apes.

Lucy’s unique lower body muscle structure would have helped her adapt to life in the open grasslands as well as dense forests, according to the researchers.

But it also means she would have walked and moved in a way that cannot be seen in any living species today.

https://www.independent.co.uk/news/uk/university-of-cambridge-east-africa-b2357008.html
 
ramonmercado said:
Lucy was no slouch.

Lucy, the world’s most famous early human ancestor, had knee joints that allowed her to walk fully upright as well as strong leg and pelvic muscles suited to living in trees, research suggests.

For the first time, scientists at the University of Cambridge digitally reconstructed the lower limb muscles of the extinct ape-like relative who lived in Africa more than three million years ago.

The results, published in the journal Royal Society Open Science, suggest Lucy could straighten her knee joints, giving her the ability to stand upright and walk on two legs with an erect posture, similar to modern-day humans.

The team also found that her leg muscles were bigger and more powerful than those seen in modern humans, enabling her to live in trees like apes.

Lucy’s unique lower body muscle structure would have helped her adapt to life in the open grasslands as well as dense forests, according to the researchers.

But it also means she would have walked and moved in a way that cannot be seen in any living species today.

https://www.independent.co.uk/news/uk/university-of-cambridge-east-africa-b2357008.html
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Wonder whether the walk is anything like that reported for any of the small hominid cryptids reported from various places?
 
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