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Author Topic:   New Human Fossil Shows Unique MtDNA
Granny Magda
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Posts: 2462
From: UK
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Message 1 of 14 (551882)
03-25-2010 12:01 AM


Don't get too excited, it's just a finger-bone. It does have apparently non-sapiens mitochondrial DNA though. It is being interpreted as a new species.
quote:
DNA identifies new ancient human dubbed 'X-woman'
Scientists have identified a previously unknown type of ancient human through analysis of DNA from a finger bone unearthed in a Siberian cave.
The extinct "hominin" (human like creature) lived in Central Asia between 48,000 and 30,000 years ago.
An international team has sequenced genetic material from the fossil showing that it is distinct from that of Neanderthals and modern humans.
Full article here.
This raises the interesting idea of multiple human species inhabiting Pleistocene Asia alongside one another.
Mutate and Survive

"A curious aspect of the theory of evolution is that everybody thinks he understands it." - Jacques Monod

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hooah212002
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Posts: 3193
Joined: 08-12-2009


Message 2 of 14 (551883)
03-25-2010 12:19 AM
Reply to: Message 1 by Granny Magda
03-25-2010 12:01 AM


Funny thing: the first article I saw about this was something somewhere about how it debunks evolution. I've yet to really read more on it as anything I've seen so far appears to be nothing more than hype.

"Some people think God is an outsized, light-skinned male with a long white beard, sitting on a throne somewhere up there in the sky, busily tallying the fall of every sparrow. Othersfor example Baruch Spinoza and Albert Einsteinconsidered God to be essentially the sum total of the physical laws which describe the universe. I do not know of any compelling evidence for anthropomorphic patriarchs controlling human destiny from some hidden celestial vantage point, but it would be madness to deny the existence of physical laws."-Carl Sagan
"Show me where Christ said "Love thy fellow man, except for the gay ones." Gay people, too, are made in my God's image. I would never worship a homophobic God." -Desmond Tutu

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Coyote
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Posts: 6117
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Message 3 of 14 (551886)
03-25-2010 1:03 AM
Reply to: Message 2 by hooah212002
03-25-2010 12:19 AM


Debunks evolution?
the first article I saw about this was something somewhere about how it debunks evolution.
Debunks evolution? Some folks interpret any change in evolutionary theory or improvement of our database as evidence that we were wrong before, and most likely wrong again. The Dishonesty Institute is well known for this. It's nothing more than religious apologetics.
What this find seems to show is that there is a new mtDNA type back some 50,000 years or more. Given the number of specimens we have that are so old, this is not surprising. This is a new field, and these results have only been coming in the past few years.
About ten years ago I submitted a bone that was dated to about 4,800 years ago and repeated extractions could not find usable mtDNA. (A tooth from the same site yielded good results at 5,300 years ago.) Techniques have improved so much in that short time that 50,000+ years is becoming possible, and the Planck folks are about the best there is right now.
Look to see a lot of new and exciting data, and changes in existing data, in the years to come. That's the way science works, whether the religious apologists say yea or nay.

Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

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Dr Jack
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Message 4 of 14 (551904)
03-25-2010 6:37 AM
Reply to: Message 1 by Granny Magda
03-25-2010 12:01 AM


How does non-sapiens mtDNA imply it's a new species? We know, for a fact, that mtDNA lines die out from time to time why not interpret this as an extinct mtDNA line rather than a distinct species?

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Huntard
Member (Idle past 2285 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 5 of 14 (551905)
03-25-2010 6:42 AM
Reply to: Message 4 by Dr Jack
03-25-2010 6:37 AM


Wouldn't sapiens MtDNA need to contain certain genetic markers that identify it as sapiens MtDNA? I mean, it's not like it can be made up out of any random combination, could it?

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Wounded King
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Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 6 of 14 (551907)
03-25-2010 7:00 AM
Reply to: Message 4 by Dr Jack
03-25-2010 6:37 AM


It is less closely related to H. Sapiens mtDNA than Neanderthal DNA. I don't see how this could be an extinct H. Sapiens mtDNA lineage and still fit in with a common ancestry model. We would still expect extinct human mtDNA lineages to be more similar to other humans, as currently extant human mtDNA lineages are.
TTFN,
WK

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Dr Jack
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Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


Message 7 of 14 (551909)
03-25-2010 7:07 AM
Reply to: Message 6 by Wounded King
03-25-2010 7:00 AM


Having been off and read the Nature letter, I tend to agree. It's still possible although unlikely that this simply represents a unusual mtDNA:
quote:
[Eske] Willerslev [(an evolutionary biologist and director of the Centre for GeoGenetics at the University of Copenhagen)] emphasizes that, on its own, the mtDNA evidence does not verify that the Siberian find represents a new species because mtDNA is inherited only from the mother. It is possible that some modern humans or Neanderthals living in Siberia 40,000 years ago had unusual mtDNA, which may have come from earlier interbreeding among H. erectus, Neanderthals, archaic modern humans or another, unknown species of Homo. Only probes of the nuclear DNA will properly define the position of the Siberian relative in the human family tree.
  —Nature

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RAZD
Member (Idle past 1395 days)
Posts: 20714
From: the other end of the sidewalk
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Message 8 of 14 (551910)
03-25-2010 7:13 AM
Reply to: Message 7 by Dr Jack
03-25-2010 7:07 AM


one piece of evidence, one set of assumptions
Hi Folks,
I find it curious that they take the divergence date as fixed, based on one piece of evidence, rather than subject to validation with more information:
quote:
The divergence date of one million years is too young for the Denisova hominin to have been a descendent of Homo erectus, which moved out of Africa into Asia some two million years ago.
And it is too old to be a descendent of Homo heidelbergensis, another ancient human thought to have originated around 650,000 years ago. However, for now, the researchers have steered away from describing the specimen as a new species.
This divergence date is based on many assumptions, and one of them is that there is a steady rate of changes when we know that this is not so.
To my mind this could easily be one or the other of these candidates.
Or a Yeti ...
The NATURE letter is at
Fossil finger points to new human species | Nature
Published online 24 March 2010 | Nature 464, 472-473 (2010) | doi:10.1038/464472a
Enjoy.
Edited by RAZD, : nature article link

we are limited in our ability to understand
by our ability to understand
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Dr Jack
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Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


Message 9 of 14 (551914)
03-25-2010 7:38 AM
Reply to: Message 8 by RAZD
03-25-2010 7:13 AM


Re: one piece of evidence, one set of assumptions
I find it curious that they take the divergence date as fixed, based on one piece of evidence, rather than subject to validation with more information
Er, they don't. They take both the Neanderthal/Human and Denisova/human/neanderthal splits as subject to large (non-overlapping) margins of error. But, if you read the letter, their main argument for seperate species status is the construction of the cladogram which groups the Devisova hominid on a seperate branch to all the human and neanderthal samples.

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RAZD
Member (Idle past 1395 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 10 of 14 (552001)
03-25-2010 6:14 PM
Reply to: Message 9 by Dr Jack
03-25-2010 7:38 AM


Re: one piece of evidence, one set of assumptions
Hi Mr Jack,
They take both the Neanderthal/Human and Denisova/human/neanderthal splits as subject to large (non-overlapping) margins of error.
I also note that the Nature letter was much less emphatic about the genetic divergence dates, so that is more likely a result of reporters not understanding the science than that the scientists were emphatic about the dates.
I just find the whole issue of generating dates from genetic information to be a little untested at this time to say with any assurance that the divergence dates are known with any reliability. To me, all we have is relative information, much like the relative information on dating provided by sedimentary layers: we know what sequence is involved to a fairly good degree, but absolute dates are not derived from this kind of data.
But, if you read the letter, their main argument for seperate species status is the construction of the cladogram which groups the Devisova hominid on a seperate branch to all the human and neanderthal samples.
Which doesn't rule out erectus and heidelburgensis, which we also know left africa for europe and asia, especially erectus (java man). I'm not aware of any DNA evidence of erectus or heidelburgensis, so assuming a new species seems pretty premature at this point.
Enjoy

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

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Coyote
Member (Idle past 2096 days)
Posts: 6117
Joined: 01-12-2008


Message 11 of 14 (552012)
03-25-2010 8:24 PM
Reply to: Message 10 by RAZD
03-25-2010 6:14 PM


Re: one piece of evidence, one set of assumptions
I'm not aware of any DNA evidence of erectus or heidelburgensis, so assuming a new species seems pretty premature at this point.
One other piece of information: the fossils do not (yet) suggest another species in that time period. Paleontologists have been digging like mad for close to 200 years, and the mtDNA is the first clue to another species here.
And I would still like to see what the mtDNA or DNA of Florensis might be. The mandible I saw pictured looks like it has some nice teeth to work with. If the Planck guys can do a finger bone a tooth should be easy!

Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


Message 12 of 14 (552047)
03-26-2010 5:22 AM
Reply to: Message 10 by RAZD
03-25-2010 6:14 PM


Re: one piece of evidence, one set of assumptions
I just find the whole issue of generating dates from genetic information to be a little untested at this time to say with any assurance that the divergence dates are known with any reliability. To me, all we have is relative information, much like the relative information on dating provided by sedimentary layers: we know what sequence is involved to a fairly good degree, but absolute dates are not derived from this kind of data.
Hmm.... it has problems to be sure. But I think it's pretty sound in many cases; certainly good enough to make tentitive judgements from. When the conditions are right (primarily not parasites, not domesticated) it pases both external and internal tests of reliability - although the margins of error remain large.

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Dr Jack
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Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


Message 13 of 14 (552048)
03-26-2010 5:23 AM
Reply to: Message 11 by Coyote
03-25-2010 8:24 PM


Re: one piece of evidence, one set of assumptions
And I would still like to see what the mtDNA or DNA of Florensis might be. The mandible I saw pictured looks like it has some nice teeth to work with. If the Planck guys can do a finger bone a tooth should be easy!
Sadly not. The Florensis bones were recovered from waterlogged conditions - where DNA doesn't survive long.

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sfs
Member (Idle past 2524 days)
Posts: 464
From: Cambridge, MA USA
Joined: 08-27-2003


Message 14 of 14 (552512)
03-29-2010 4:29 PM
Reply to: Message 10 by RAZD
03-25-2010 6:14 PM


Re: one piece of evidence, one set of assumptions
The authors of the paper go out of their way to avoid using the word "species" to describe their individual. They talk about "types" or "forms" of hominin, but do not commit themselves to any conclusions about species status. (Note: they have also sequenced the nuclear genome of this sample, which will no doubt reveal much more about the relationship with sapiens and neandertals, once they get around to publishing.)

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