Evolutionary Spin
"The picture of her genome is as accurate as that of modern day human genomes,
and shows she had brown eyes, hair and skin.
The research
in Science also sheds new light on the genetic differences between modern
humans and their closest extinct relatives.
The cave dweller, a Denisovan, was a cousin of the Neanderthals.
Both groups of ancient humans died out about 30,000 years ago, but have left
their mark in the gene pool of modern people.
Shadowy
past
The Denisovans have mysterious origins. They appear to have left little
behind for palaeontologists save a tiny finger bone and a wisdom tooth found in
Siberia's Denisova cave in 2010.
Though some researchers have proposed a possible link between the Denisovans
and human fossils from China that have previously been difficult to
classify.
A Russian scientist sent a fragment of the bone from Siberia to a team led by
Svante Paabo at the Max Planck Institute for Evolutionary Anthropology in
Leipzig, Germany.
He thought it might belong to an early modern human, but the results came as
a surprise.
DNA analysis revealed a human who was neither a Neanderthal nor a modern
human but the first of a new group of ancient humans.
Gene catalogue
 |
| People with largest percentage of Denisovan DNA |
Dr Paabo's team has now sequenced the genome of the Denisovan in much greater
depth, using a new technique for studying ancient DNA.
The quality of the genome sequence is similar to that seen in genome studies
of modern day humans.
The scientists compared the girl's genome with that of Neanderthals and 11
modern humans from around the world.
This allowed them to catalogue the gene changes that make modern humans
different from the two groups of extinct humans that were their closest
relatives.
They include changes to only a single DNA letter in several genes involved in
the wiring of the brain and nervous system, as well as those that affect the eye
and the skin.
The most detailed genetic analysis yet of the Denisovans also confirms that
they bred with the ancestors of some people alive today, the researchers
said.
It shows that about 3% of the genes of people living today in Papua New
Guinea come from Denisovans, with a trace of their DNA lingering in the Han and
Dai people from mainland China.
The genetic variation of Denisovans was very low, suggesting that although
they were found in large parts of Asia their population remained small." BBC
Creationist Response
"Widespread news reported that scientists sequenced ancient DNA from an extinct human variety that they called a Denisovan in unprecedented detail for ancient DNA. In 2011, researchers reported DNA sequence from the tiny finger bone that had been lying in Siberia's Denisova Cave, but the sequence was not of high enough quality to compare base-for base to the modern human genome. Now it is.Researcher Matthias Meyer pioneered a technique that sequences ancient and, therefore, fragmented single strands of DNA. Older methods could only sequence larger, double-stranded DNAs.
Meyer was lead author of a paper published in Science, successful in "producing a 'near-complete' catalog of the small number of genetic changes that make us different from the Denisovans, who were close relatives of Neandertals," according to Science writer Ann Gibbons. So, what kind of creature do the Denisovans represent, and what role might they have played in human history?
First, Neandertals were fully human and interbred with modern man. Second, this Denisovan DNA only differed from Neandertal by a "small number of genetic changes," indicating a close relation.
The Denisovan finger bone fragment was initially identified as modern human. And the same cave held fully human tools and bones. Harvard Medical School population geneticist David Reich coauthored the online Science report. NPR host Ira Flatow interviewed him:
FLATOW: Do you think that humans might have mated with Denisovans, as they did with Neanderthals?
REICH: I think that we are sure that that happened.
The team found Denisovan-specific DNA sequence in people from Papua New Guinea.REICH: I think that we are sure that that happened.
Denisovans and Neandertals clearly appear to have been varieties of human. But when did they live? Science reported "very rough dates of 30,000 to more than 50,000 years for the layers of sediment where the fossils of Denisovans, Neandertals, and of modern humans were all found." But when geneticists dated the Denisovan using DNA mutation rates—rates that are routinely calibrated to the assigned age of fossil remains—they estimated that it could have been deposited around 80,000 years ago. Reich told NPR, "So we have a date in the paper, and it's embarrassingly uncertain." He said that the uncertainty is due to ignorance of the mutation rate.
Since the archaeological date is "very rough," and the molecular clock date is "embarrassingly uncertain," and since the two are in discord, perhaps none of those estimates are accurate.
In the context of biblical creation, Denisovans and Neandertals are extinct varieties of mankind—descendants of Noah's three sons—that lived probably within several hundred years of the Flood. This is consistent with the fact that their remains were found together in this cave and with the fact that their DNA sequences are so clearly human.
The high-resolution sequencing of ancient DNA is a technological achievement that certainly does enable researchers to better characterize these "Ancient Relatives: The Denisovans." They were relatives, and they were ancient, but not nearly as ancient as claimed." ICR
Woe unto him that striveth with his Maker!
Let the potsherd strive with the
potsherds of the earth. Shall the clay say to him that fashioneth it, What
makest thou?
or thy work, He hath no hands?
Isaiah 45:9
