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Homo Naledi

 
 
Reply Tue 9 May, 2017 10:29 am
https://www.theverge.com/2017/5/9/15591814/homo-naledi-discovery-bone-dating-human-evolution
Two years ago, scientists announced the discovery of a puzzling new species of early human: Homo naledi. The 15 partial skeletons were uncovered deep inside a cave in South Africa — and featured human-like hands and feet, but surprisingly small brains the size of a gorilla's (a third the size of modern human's). The discovery of H. naledi, however, lacked one key piece of information: the age of the bones. Now, the team of researchers who uncovered H. naledi announced the fossils are between 236,000 and 335,000 years old, according to National Geographic. If the dates are confirmed, that means H. naledi is much younger than its primitive features suggest, and they may have lived around the same time our own species — Homo sapiens — was evolving.

The discovery, published today in the journal eLife, is likely to be controversial, because it could mean that the stone tools uncovered in South Africa from the time — called the Middle Stone Age — weren’t made by modern humans. Today’s research is controversial for another reason: the researchers describe the discovery of a second cave chamber, where a bunch of other H. naledi remains were found. That may confirm one contested hypothesis first put forward in 2015: that H. naledi used the Rising Star cave to bury its dead. That’s a very complex and modern behavior, and some scientists believe that such primitive humans couldn’t have performed it.

MUCH YOUNGER THAN ITS PRIMITIVE FEATURES SUGGEST
The first cave chamber, called Dinaledi, was discovered in 2013. It contained over 1,500 specimens of H. naledi — the largest single paleoanthropological find of its type in Africa. The chamber is deep underground, and could be accessed only by a team of female scientist-climbers specially selected to fit through a narrow, vertical shaft that was just eight inches wide at points. The second chamber, called Lesedi, is also similarly hard to reach, and contains remains from about 130 specimens, including one adult skeleton that’s very well preserved.

Both chambers only contain H. naledi remains (although some animal remains were found inside Lesedi). That suggests H. naledi used to site to bury its dead. And the discovery of the second chamber bolsters that hypothesis, according to the research team led by University of the Witwatersrand paleoanthropologist Lee Berger. “What are the chances that you have some natural phenomenon that has left accumulations of multiple bodies, adults and juveniles, in two far-separated parts of the cave, in very similar depositional circumstances — and we found both of them?” John Hawks, a paleoanthropologist at the University of Wisconsin-Madison, who’s part of the research team, told National Geographic. “It’s very difficult to believe that this is some kind of coincidence.”


But some disagree, saying that the bodies could have been deposited in the caves naturally — maybe they were washed there by floods. There are no artifacts in the cave, so it’s hard to interpret the meaning of the remains, Alison Brooks, a paleoanthropologist at George Washington University and the Smithsonian Institution who wasn’t involved in the research, told The Washington Post.

To date the H. naledi remains found in the first cave chamber, the researchers used six different dating techniques, each tried independently by two labs to confirm the results, according to The Washington Post. (The remains in the new cave chamber haven’t been dated yet.) The team analyzed the H. naledi teeth, the layers of calcite deposited through time on the bones, and the cave’s radioactivity — and determined the fossils date to between 236,000 and 335,000 years ago. That’s much younger than the team previously thought: H. naledi shares some features with early members of our genus that lived nearly 2 million years ago, so the researchers thought the H. naledi fossils would be around the same age. Today’s finding, however, dispels that, and could mean that H. naledi was a lingering lineage that arose about 2 million years ago, and stuck around at a time when a bunch of other early human ancestors roamed the planet.

HOW H. NALEDI FITS INTO THE HUMAN FAMILY TREE ISN’T CLEAR YET
In fact, during the Middle Stone Age, there were Neanderthals, Denisovans, and Homo erectus, as well as other hominins. How H. naledi fits into the human family tree isn’t clear yet. Could it be that H. naledi, not H. erectus, is our most immediate ancestor? It’s impossible to tell for now, but what’s clear is that the H. naledi discovery paints a much more complicated picture. And more research is needed before conclusions are reached.

“The past was a lot more complicated than we gave it credit for and our ancestors were a lot more resilient and lot more varied than we give them credit for,” Susan Anton, a paleoanthropologist at New York University who was not involved in the study, told The Washington Post. “We're not the pinnacle of everything that happened in the past. We just happen to be the thing that survived.”
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Blickers
 
  1  
Reply Tue 9 May, 2017 10:59 am
@edgarblythe,
Quote article:
Quote:
but surprisingly small brains the size of a gorilla's (a third the size of modern human's).

Brain size is frequently stated as brain size-to-body mass ratio. Homo naledi was physically small. The males had a brain volume of approximately 565 cc and a body mass of 100 lbs, (height was 5ft even). Modern male brain volume is 1250 cc and a body weight of 150 lbs, (female brain volume and body weight is slightly smaller, the ratio works out about even to males). So the brain volume/body mass ratio of Homo naledi is smaller than that of modern humans, but it is not one third the size-it is closer than that. It is more like 68% of the modern humans' brain size/body mass ratio.
farmerman
 
  1  
Reply Tue 9 May, 2017 11:57 am
@Blickers,
This is how evolution works. New forms come into being via the "crapshoot" of mutation. The existing "Idaltu" forms hang around till they are selected out by some benefit the newer form sports within its "genetic toolkit"
Remember H neanderthalensis had a bigger cranial capacity than H s.s
.
farmerman
 
  2  
Reply Tue 9 May, 2017 11:59 am
@Blickers,
great point. Cranial/body mass ratios of true hominins hover around the 62-68% neighborhood
0 Replies
 
farmerman
 
  1  
Reply Tue 9 May, 2017 12:10 pm
I hope they did U/Ca on the ,imestone. LIMESTONE is a real bitch to get accurqte dates . Too much contamination by older(and younger) leach water dissolving rok of all ages.
I figured that the forst articles pub'd in the National Geographic were kinda bullshit for a cave deposit. The new values are almost 10 times younger.

STILL, they dont even mention what their gc standards were
0 Replies
 
Setanta
 
  1  
Reply Tue 9 May, 2017 12:54 pm
Thanks for the article, EB.
farmerman
 
  1  
Reply Sun 21 May, 2017 06:43 pm
@Setanta,
been quiet for a week or more, they just ran an article in sigma xi "Am Scientist" , but its mostly about the second layer of bones in room 2.
Looks like a repository for soles
0 Replies
 
Blickers
 
  1  
Reply Sun 21 May, 2017 10:04 pm
@farmerman,
Quote farmerman:
Quote:
The existing "Idaltu" forms hang around till they are selected out by some benefit the newer form sports within its "genetic toolkit"


I notice that you mention Homo Sapien Idaltu quite a bit. As I understand it, Homo Sapien Idaltu was a subspecies name given to the remains found at Herto Ethiopia, dated to 150,000 years ago. Then the bones at Omo, Ethiopia were dated to 195,000 years ago. This would not be so remarkable except for that the 195,000 years old Omo bones were somewhat more gracile and modern looking than the 150,000 year old "Idaltu" bones.

After this finding came out, apparently the consensus opinion was to simply regard ancient Homo Sapien groups as being very diverse as regards features, and to simply drop the "Idaltu" label from the Herto bones and consider then Homo Sapien.

Are you saying that the 150,000 year old Idaltu bones really are a separate subspecies from 195,000 year old Omo bones?
farmerman
 
  1  
Reply Mon 22 May, 2017 04:37 am
@Blickers,
I read online some of the other developmental anthro stuff. Its a kind of group title that(I think) Svante P'aabo first started using based on some genetics work where "idaltu" was used not only as a specific regional form, it was also used in inclusive terms of a "type section "name where certain specific characters were detected in derived skull forms and were called idaltu.

Were not so much gonna confuse anyone here so Im not being any more particluar than when Id also hear "neanderthal" used as a crude group name.

Still, it does say "old ones" and implies a type section as well as a time line. I do it on purpose to hopefully familiarize folks with the other side of the Horn of Africa besides just Laeotoli and the western rifts.
farmerman
 
  1  
Reply Mon 22 May, 2017 04:49 am
@farmerman,
there was another thing about the "levantine" type skulls that resemble the original idaltu and then the Omo skulls. Omo was typed using mitochondrial DNa and all the Herto and LEvantine "idaltus" were Y chromosomal so the hplogroups may actually converge and were looking at features that were incorrectly typed as sub secies rather than (a possibiility) that we are merely looking at sexual dimorphism or polymorphism in general .
Im no expert on this, Im just guilty of reading lots of ancient origins papers from the web and there are lumpers and splitters. Ima lumper
Blickers
 
  1  
Reply Mon 22 May, 2017 09:36 pm
@farmerman,
By Levantine, you mean the skulls at Shkul and Qafzeh? They were long theorized, before DNA sampling was used, as Sapien Neanderthal crosses. Now one of them is being identified at the moment as Homo Heidelbergensis, which is somewhat interesting. Researchers had struggled for a long time to classify Heidelbergensis, because it was being humorously referred to as the "Muddle In The Middle"-not quite Erectus, but not quite Sapien or Neanderthal.

So now we're back to Square One with Heidelbergensis.
0 Replies
 
Walter Hinteler
 
  1  
Reply Mon 22 May, 2017 11:11 pm
The latest research will add some discussions:

Potential hominin affinities of Graecopithecus from the Late Miocene of Europe
0 Replies
 
 

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