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This Is How a 3.2 Million Year Old Human Relative Walked

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AnonymousAnonymous
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13 Jun 2023, 8:16 pm

https://www.cnn.com/2023/06/13/world/lucy-fossil-bipedalism-scn/index.html


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14 Jun 2023, 12:55 am

Bipedalism is the base for apes. Knuckle-walking is a derived trait that evolved separately and repeatedly in non-human apes.


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14 Jun 2023, 4:41 pm

I thought humans separated from chimps at 3,3 million?



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14 Jun 2023, 4:45 pm

cyberdad wrote:
I thought humans separated from chimps at 3,3 million?


Quote:
The chimpanzee–human last common ancestor (CHLCA) is the last common ancestor shared by the extant Homo (human) and Pan (chimpanzee and bonobo) genera of Hominini. Due to complex hybrid speciation, it is not currently possible to give a precise estimate on the age of this ancestral population. While "original divergence" between populations may have occurred as early as 13 million years ago (Miocene), hybridization may have been ongoing until as recently as 4 million years ago (Pliocene).


Also:

Quote:
No fossil has yet conclusively been identified as the CHLCA. A possible candidate is Graecopithecus. This would put the CHLCA split in Southeast Europe instead of Africa.

Sahelanthropus tchadensis is an extinct hominine with some morphology proposed (and disputed) to be as expected of the CHLCA, and it lived some 7 million years ago – close to the time of the chimpanzee–human divergence. But it is unclear whether it should be classified as a member of the tribe Hominini, that is, a hominin, as an ancestor of Homo and Pan and a potential candidate for the CHLCA species itself, or simply a Miocene ape with some convergent anatomical similarity to many later hominins.

Ardipithecus most likely appeared after the human-chimpanzee split, some 5.5 million years ago, at a time when hybridization may still have been ongoing. It has several shared characteristics with chimpanzees, but due to its fossil incompleteness and the proximity to the human-chimpanzee split, the exact position of Ardipithecus in the fossil record is unclear. It is most likely derived from the chimpanzee lineage and thus not ancestral to humans. However, Sarmiento (2010), noting that Ardipithecus does not share any characteristics exclusive to humans and some of its characteristics (those in the wrist and basicranium), suggested that it may have diverged from the common human/African ape stock prior to the human, chimpanzee and gorilla divergence.


Source: https://en.wikipedia.org/wiki/Chimpanze ... n_ancestor


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14 Jun 2023, 5:25 pm

I know the dates are being thrown around but the existence of a bipedal semi-human ape does not necessarily = our ancestor

there is a tendency to look for characteristics that morphologically adjacent or closer to modern humans and insert it into an artificial chronological time-line. This is a form of anthropomorphism.



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14 Jun 2023, 5:32 pm

cyberdad wrote:
I know the dates are being thrown around but the existence of a bipedal semi-human ape does not necessarily = our ancestor


Who else would our ancestor be? :chin:

Don't say aliens. :roll:

You're right though that not every single upright ape is bound to be our direct ancestor, but what does that have to do with the idea that basal great apes walked upright?


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14 Jun 2023, 8:33 pm

cyberdad wrote:
I thought humans separated from chimps at 3,3 million?


I have never heard that figure.

The split between humans and chimps is thought to have occurred at least five million years ago, and most likely seven to 8 million years ago. Thats based upon DNA evidence. But the fossil record doesnt contradict.

Lucy was long past that fork in the road and was moving down the road toward us humans (either our ancestor or a close cousin of our ancestor).

We know about primates far older than the split, and we know about hominid fossils younger than Lucy. But fossils from the time of the split are rare- the time period is tantalizing black hole. So thats why discoveries that push things back to that time are so important.

Read the book about her written 20 years ago. Lucy had a fascinating mosaic of both chimplike and humanlike traits, but was clearly akin to us.

This article ends with a rather inconclusive conclusion. They quote the scientist as saying "if she walked on two legs like us...then she would have walked on two legs just like us". :lol: Seeming tautology.

I think that they MEAN that "if Lucy chose to walk on two legs...at a particular moment...then she could walk just like us. But she also had options we no longer have... of walking on all fours...or she could also haul herself up into a tree in the blink of an eye" because her arms were longer and more powerful than ours.



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14 Jun 2023, 8:44 pm

There's differences in the shoulder anatomy too. My understanding is that increased selection for (overhand) throwing ability amounts to selecting against climbing ability, which is why archaic humans steadily became worst climbers.


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15 Jun 2023, 1:59 am

naturalplastic wrote:
I have never heard that figure.

I can't find the original source but it's close to this ball park
https://www.nbcnews.com/id/wbna17302266



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15 Jun 2023, 2:02 am

funeralxempire wrote:
There's differences in the shoulder anatomy too. My understanding is that increased selection for (overhand) throwing ability amounts to selecting against climbing ability, which is why archaic humans steadily became worst climbers.


There would have been an overlap, early bipedalism would not facilitate running so probably up to 3 million years ago any bipedalism would be accompanied by all 4s in order to escape hungry predators.



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15 Jun 2023, 12:58 pm

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:-| I hope I'm walking that well when I'm 3.2 million years old!


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15 Jun 2023, 1:05 pm

cyberdad wrote:
funeralxempire wrote:
There's differences in the shoulder anatomy too. My understanding is that increased selection for (overhand) throwing ability amounts to selecting against climbing ability, which is why archaic humans steadily became worst climbers.


There would have been an overlap, early bipedalism would not facilitate running so probably up to 3 million years ago any bipedalism would be accompanied by all 4s in order to escape hungry predators.


An upright stance was the norm for hominid apes as far back as Morotopithecus. Your entire framing of 'early bipedalism' is flawed because bipedalism is a basal trait that had been around for millions of years before Australopithecus came around.

Quote:
For most of the past two hundred years, models of the origin of human upright posture and bipedalism have been based primarily on evidence from the appendicular and cranial skeleton, but evidence from the spine has played little or no role in our understanding. A series of discoveries of axial skeletal fossils from species including Morotopithecus bishopi [47], [49], Proconsul nyanzae [45], Oreopithecus bambolii [50], [51] and Pierolapithecus catalaunicus [52] have now provided evidence that is remarkably inconsistent with models that have not considered axial structures in understanding posture.

Given the many unique aspects of load bearing and movement requirements, it is not at all surprising that the lumbar vertebrae of modern humans are strikingly different in structure and function from typical mammalian vertebrae. However, the appearance of most of the unique features of the Homo sapiens lumbar vertebra in UMP 67-28, a hominoid fossil from 21.6 million years ago [37], [47], [49] is very surprising. This is particularly true since the apes of the Early and Middle Miocene have been generally considered to have few or none of the modifications of body plan that characterize modern apes and humans.

For a variety of reasons, the term “human” has been applied to a clade of hominoids commencing at the split from the chimpanzee lineage about six million years ago. The basis for this distinction has been upright bipedalism exclusively in the human lineage. However, when the evidence from serial axial structures and homeotic events are considered, the anatomical basis for upright posture and bipedalism appears to have arisen far earlier–it is the axial anatomy first seen in Morotopithecus. Upright bipedalism plays a significant role in all the species of a clade that share the morphogenetic transformation with Morotopithecus.


Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2000357/


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15 Jun 2023, 2:35 pm

funeralxempire wrote:
cyberdad wrote:
I know the dates are being thrown around but the existence of a bipedal semi-human ape does not necessarily = our ancestor


Who else would our ancestor be? :chin:

Don't say aliens. :roll:

You're right though that not every single upright ape is bound to be our direct ancestor, but what does that have to do with the idea that basal great apes walked upright?

Anunnakis. 8)


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15 Jun 2023, 2:49 pm

goldfish21 wrote:
funeralxempire wrote:
cyberdad wrote:
I know the dates are being thrown around but the existence of a bipedal semi-human ape does not necessarily = our ancestor


Who else would our ancestor be? :chin:

Don't say aliens. :roll:

You're right though that not every single upright ape is bound to be our direct ancestor, but what does that have to do with the idea that basal great apes walked upright?

Anunnakis. 8)


I know that's what Zecharia Sitchin and David Icke would suggest, but... well.. they're crackpots who lack any credibility.


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15 Jun 2023, 8:45 pm

re: the article
For a variety of reasons, the term “human” has been applied to a clade of hominoids commencing at the split from the chimpanzee lineage about six million years ago"

Herein lies two fundamental problems
1. The actual date when humans split from chimps is really not that rock solid. From the literature I posted it ranges from 3.5 million to 8 million. Given our genetic similarity with chimps (99.98% homologous) I tend to lean toward a more recent split.

2. The term applied to "human" has really been subjective when it comes to the fossil record. A good example are neanderthals, For almost a century neanderthals were erroneously published as little more than bipedal apes. Genetics has completely blown that theory out of the water.



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15 Jun 2023, 8:54 pm

cyberdad wrote:
re: the article
For a variety of reasons, the term “human” has been applied to a clade of hominoids commencing at the split from the chimpanzee lineage about six million years ago"

Herein lies two fundamental problems
1. The actual date when humans split from chimps is really not that rock solid. From the literature I posted it ranges from 3.5 million to 8 million. Given our genetic similarity with chimps (99.98% homologous) I tend to lean toward a more recent split.

2. The term applied to "human" has really been subjective when it comes to the fossil record. A good example are neanderthals, For almost a century neanderthals were erroneously published as little more than bipedal apes. Genetics has completely blown that theory out of the water.


The most straightforward way to understand things is to recognize gorillas and chimps as two out-branches of the walking apes (us). Each developed knuckle walking independently, as indicated by the differences between how each of them knuckle walks.

With chimps it seems undeniable that the split wasn't a one-and-done incident, but instead that the populations remained similar enough to crossbreed for several million years, meaning the split could have even potentially undone itself had the two semi-distinct populations continued to crossbreed heavily.


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