Smaller hominid family tree?
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28-10-2013, 10:31 AM
Smaller hominid family tree?
I always thought this was interesting to think about, the blurred lines between speciation, and variation with in a specie. 1.8 million year old skull challenges the idea of the number of early Homo species...and if only this came along some time ago, it could have save me a headache remembering all those species names in college...or at least three of them...or I guess only really two.

original artical here

[Image: Georgian_Hominid_Skull.jpg]

The idea that there were several different human species walking the Earth two million years ago has been dealt a blow.

Instead, scientists say early human fossils found in Africa and Eurasia may have been part of the same species.

Writing in the journal Science, the team says that Homo habilis, Homo rudolfensis and Homo erectus are all part of a single evolving lineage that led to modern humans.

But others in the field reject this.

A team looked at the most complete hominid skull ever found, which was uncovered in Dmanisi, Georgia.

It had a small braincase, large teeth and a long face, characteristics it shares with H. habilis. But many features from the braincase were also "unique" to H. erectus.
The 1.8-million-year old skull comes from a site that has given up the biggest collection of well-preserved early-human remains known anywhere in the world.
The Dmanisi collection also represents the earliest evidence of primitive humans outside Africa, a group that emerged soon after early Homo diverged from Australopithecus, or "Lucy".

"We now have the best evidence for what early Homo really is," said lead author David Lordkipanidze from the Georgian National Museum in Tbilisi, Georgia.

"One of the most important things is that we have such a remarkable collection; it's very rare that you have that from one site."
The fossil remains showed a lot of variation that had previously puzzled researchers, but Prof Lordkipanidze said it was clear that these features were all from one population.

"When we looked at this variability and compared it with modern humans, you can see this is a normal range of variation," Prof Lordkipanidze told BBC News.

The skull was uncovered eight years ago and since then the team has compared it to other Homo fossils found in Africa from as early as 2.4 million years ago.

The comparative analysis of the hominid cranium revealed enough similarities for the team to consider the earliest Homo fossils as the same species as the Dmanisi hominids.

A co-author of the study, Christoph Zollikofer from the Anthropological Institute and Museum in Zurich, Switzerland, said that if the braincase and the face of "Skull 5" had been found as separate fossils at different sites in Africa, they might have been attributed to different species.

"That's because Skull 5 unites some key features, like the tiny braincase and large face, which had not been observed together in an early Homo fossil until now.

"Furthermore, since we see a similar pattern and range of variation in the African fossil record, it is sensible to assume that there was a single Homo species at that time in Africa," Prof Zollikofer added.

"And since the Dmanisi hominids are so similar to the African ones, we further assume that they both represent the same species."

Other palaeoanthropologists, however, believe that at least three distinct species of humans co-existed in Africa.

They include Fred Spoor from University College London. He told BBC News that the methods of analysis that the team used were not sufficient to infer that these fossils were the same species.

"They do a very general shape analysis of the cranium which describes the shape of the face and braincase in broad sweeping terms," Prof Spoor said.

"The problem is that those Homo species are not defined using such a broad overview of what their general cranial shape is."

He added that the very specific characteristics that had been used to define H. erectus, H. habilis and H. rudolfensis "were not captured by the landmarks that they used".

"They did not consider that the thick and protruding brow ridges, the angular back of the braincase; and some details of the base of the cranium are derived features for H. erectus, and not present in H. habilis and H. rudolfensis."

Chris Stringer at the Natural History Museum in London said that the team had made an excellent case "that this remarkable new skull, with its huge jawbone", was part of the natural variation of the Dmanisi population.

But he said he was doubtful that all of the early Homo fossils could be "lumped into an evolving H. erectus lineage".

"Only H. erectus survives and becomes successful but at the origin, nature was experimenting with how to evolve humans in terms of increasing brain size," Prof Stringer told BBC News.

"Creatures were starting to use tools and eat meat, and this drove evolution, but I think it also drove diversity. The Dmanisi group is an example of the successful species that came out of that and then carried on to spread around the old world."

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28-10-2013, 10:37 AM
RE: Smaller hominid family tree?
Defining species is an exercise in sampling a continuum. And therefore heir to all the associated issues...

It's a bit of an element of human nature, to want to identify or name a new thing, instead of a variation of an old thing.

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28-10-2013, 10:48 AM
RE: Smaller hominid family tree?
I wanna see it with the clay reconstruction artists interpretation.

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28-10-2013, 10:58 AM
RE: Smaller hominid family tree?
(28-10-2013 10:37 AM)cjlr Wrote:  Defining species is an exercise in sampling a continuum. And therefore heir to all the associated issues...

It's a bit of an element of human nature, to want to identify or name a new thing, instead of a variation of an old thing.

Is that some sort of Ad Hominid argument? Big Grin

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28-10-2013, 11:25 AM
RE: Smaller hominid family tree?
The thing I find interesting about speciation is the arbitrariness of it, yet it is a thing…or is it…

I actually majored in anthropology and in particular studied physical, or biological, anthropology, which is the study of human evolution and hominid species. So I think it’s fair to say, I love this stuff. The interesting thing to consider, is when does an organism stop being that species, and becomes a new one?

As you said, it’s a continuum, which means it never really does. There is not a point. Every offspring is the same species as it’s parent, and it’s parent can say the same, and it’s grandparent, great grand parent and so on. There is no point in time that it happens, it doesn’t exist. But what about a distinct cousin many times removed? Follow it back and it’s the same.

We only call them different species when their morphology is significant, genetics vary too much, have different behaviors and sexual attraction (willingness to mate with each other). But still there are so many things that blur those lines.

Speciation is really only a concept created to understand those differences. Clearly a tiger is a different species than a lion, just as clearly a human is a different species then a Chimpanzee. But that only works if you look at it from far enough away. But when you zoom in, like with this article on hominids, it because less clear, and then extend that in either direction in time, and on again. There is no real boundary line.

In the end, and to me, the most powerful thing about the understanding of evolution, is that we kind of aren’t different species from any other species. We are all derived from one organism and all, in a very profound way, a part of that same organism. With variation on it, of course, but all part of the same thing, the same life. Kind of like the idea of, when do we stop being part of our father, or our mother? Is there really a magical moment that our father’s cell and mother’s cell is no longer part of them? For that matter, when does a piece of hair stop being part of me, or you? When does the sugar molecule of an apple stop being part of that apple? There is no magical moment. There is no smallest bite of the apple that just before the split, is still a chunk of apple, and immediately after word is not a part of the apple anymore. It’s just how we define it, so that we can understand it, as it is with speciation.

Of course, with speciation, we can see clear differences, just as I can tell that I am not my mom and my dad, but we kind of are. In class, I always thought it seemed kind of arbitrary at what point we named one fossil species, it’s own separate species. Or whether Homo sapiens 100,000 years ago are the same thing as modern humans, or Homo sapiens ~200,000 years ago. What about Homo neanderthalensis, we clearly still mated with them, and successfully at that, so are we not them? Of course we aren’t, but…kind of…aren’t we? What about Homo erectus? If one was still around today we’d probably still be able to breed with it. Can we really say we are not H. erectus anymore? Really we are just a variation on H. erectus, that we gave a new name (assuming H. erectus is actually a direct ancestor). Our cousins, H. neanderthalensis could say the same, so are we so are we both not simply variations of H. erectus, and there for both H. erectus, and not different species of H. sapiens, and H. neanderthalensis? And for that matter we are only a variation on fish. A really odd type of fish. Even chimpanzees only differ from our genome by roughly 1%. We have no evidence that it is not possible to still produce an offspring between humans and chimpanzees, a humanzee. I don’t advise that we do, but we don’t know, and if we could, could we really call them a different species? Well yeah, we obviously could, but a little less obviously.

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28-10-2013, 11:29 AM
RE: Smaller hominid family tree?
(28-10-2013 10:48 AM)sporehux Wrote:  I wanna see it with the clay reconstruction artists interpretation.

I havent' see that yet, but here is an artist depeciton of the owner of this particular skull.

[Image: jp-scull-2-popup.jpg]

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28-10-2013, 11:36 AM
RE: Smaller hominid family tree?
(28-10-2013 11:25 AM)Raptor Jesus Wrote:  The thing I find interesting about speciation is the arbitrariness of it, yet it is a thing…or is it…

I actually majored in anthropology and in particular studied physical, or biological, anthropology, which is the study of human evolution and hominid species. So I think it’s fair to say, I love this stuff. The interesting thing to consider, is when does an organism stop being that species, and becomes a new one?

As you said, it’s a continuum, which means it never really does. There is not a point. Every offspring is the same species as it’s parent, and it’s parent can say the same, and it’s grandparent, great grand parent and so on. There is no point in time that it happens, it doesn’t exist. But what about a distinct cousin many times removed? Follow it back and it’s the same.

We only call them different species when their morphology is significant, genetics vary too much, have different behaviors and sexual attraction (willingness to mate with each other). But still there are so many things that blur those lines.

Speciation is really only a concept created to understand those differences. Clearly a tiger is a different species than a lion, just as clearly a human is a different species then a Chimpanzee. But that only works if you look at it from far enough away. But when you zoom in, like with this article on hominids, it because less clear, and then extend that in either direction in time, and on again. There is no real boundary line.

In the end, and to me, the most powerful thing about the understanding of evolution, is that we kind of aren’t different species from any other species. We are all derived from one organism and all, in a very profound way, a part of that same organism. With variation on it, of course, but all part of the same thing, the same life. Kind of like the idea of, when do we stop being part of our father, or our mother? Is there really a magical moment that our father’s cell and mother’s cell is no longer part of them? For that matter, when does a piece of hair stop being part of me, or you? When does the sugar molecule of an apple stop being part of that apple? There is no magical moment. There is no smallest bite of the apple that just before the split, is still a chunk of apple, and immediately after word is not a part of the apple anymore. It’s just how we define it, so that we can understand it, as it is with speciation.

Of course, with speciation, we can see clear differences, just as I can tell that I am not my mom and my dad, but we kind of are. In class, I always thought it seemed kind of arbitrary at what point we named one fossil species, it’s own separate species. Or whether Homo sapiens 100,000 years ago are the same thing as modern humans, or Homo sapiens ~200,000 years ago. What about Homo neanderthalensis, we clearly still mated with them, and successfully at that, so are we not them? Of course we aren’t, but…kind of…aren’t we? What about Homo erectus? If one was still around today we’d probably still be able to breed with it. Can we really say we are not H. erectus anymore? Really we are just a variation on H. erectus, that we gave a new name (assuming H. erectus is actually a direct ancestor). Our cousins, H. neanderthalensis could say the same, so are we so are we both not simply variations of H. erectus, and there for both H. erectus, and not different species of H. sapiens, and H. neanderthalensis? And for that matter we are only a variation on fish. A really odd type of fish. Even chimpanzees only differ from our genome by roughly 1%. We have no evidence that it is not possible to still produce an offspring between humans and chimpanzees, a humanzee. I don’t advise that we do, but we don’t know, and if we could, could we really call them a different species? Well yeah, we obviously could, but a little less obviously.

Another way to see the problem is one of applying the term 'species' incorrectly.

Picture a phylogenetic tree. There are two dimensions - time and species.

Trying to apply one axis (species) along the other axis (time) is what gets us into trouble.

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28-10-2013, 11:41 AM
RE: Smaller hominid family tree?
It's a messy, twisited imbreeding bush.

The only real dimension is time. Can't go back and mate with something lost in time, or too far of in time. Other than that, just a mesy bush.

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28-10-2013, 11:47 AM
RE: Smaller hominid family tree?
(28-10-2013 11:41 AM)Raptor Jesus Wrote:  ...The only real dimension is time. Can't go back and mate with something lost in time...

Actually I kind of take that back. We might be able to bring back mammoths. Not to mate with, of course... That would be weird. But they may not actually be lost to time. I would be interested to see that happen.

But then, if it grow up in the amniotic environment of an african elephant's womb, would it really devolope as a true mammoth? It may take a second generation of elephant born mammoths to reproduce naturally to rasie a mammoth in a mammoth womb for it to truly develop into something that can truely be called an "offical" mammoth.

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28-10-2013, 12:44 PM
RE: Smaller hominid family tree?
(28-10-2013 11:47 AM)Raptor Jesus Wrote:  
(28-10-2013 11:41 AM)Raptor Jesus Wrote:  ...The only real dimension is time. Can't go back and mate with something lost in time...

Actually I kind of take that back. We might be able to bring back mammoths. Not to mate with, of course... That would be weird. But they may not actually be lost to time. I would be interested to see that happen.

But then, if it grow up in the amniotic environment of an african elephant's womb, would it really devolope as a true mammoth? It may take a second generation of elephant born mammoths to reproduce naturally to rasie a mammoth in a mammoth womb for it to truly develop into something that can truely be called an "offical" mammoth.

If we can breed a mammoth that way, we can breed a neanderthal that way.

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