The Denisonvans were an ancient
people who are known from only a single archaeological site, a cave in the
Altai Mountains of southern Siberia. The group were identified as being
genetically distinct after scientists studied genetic data from the fingerbone
of a child found in 2008 and thought to have lived at least 50 000 years
ago. Mitochondrial DNA from this
individual suggests that the most recent female direct ancestor that this
individual shared with Neanderthals and Modern Humans that lived about a
million years ago. This was possible because mitochondrial DNA is found in the
mitochondria, organelles outside the cell nucleus, it is passed directly from
mother to child without being sexually recombined each generation, enabling
precise estimations of when individuals shared common ancestors, at least
through the female line (it is also possible to trace direct ancestry through
the male line, using DNA from the Y chromosome, which is passed directly from
father to son without sexual recombination). However analysis of the main
nuclear DNA of the individual (DNA which is found in the nucleus of the cell
and which is recombined with each generation), suggests that he or she shared a
more recent common ancestor with Neanderthals (though clearly from a
genetically distinct and separate population), and came from a population that
had supplied about 5% of the DNA found in modern Melanesian populations and
about 0.2% of the DNA found in modern East Asian and Native American
populations.
In 2010 a foot bone was recovered
from the same site, thought to be from an individual that lived in the area at
approximately the same time (i.e. to within a few thousand years). However
genetic material recovered from this specimen revealed it to be of Neanderthal
rather than Denisovan origin.
In a paper published in the
Proceedings of the National Academy of Sciences of the United States of America
on 16 November 2015, a team of scientists led by Susanna Sawyer and Gabriel Renaud
of the Department of Evolutionary Genetics at the Max Planck Institute for Evolutionary Anthropology describe the results of a study of two molars found
in the Denisova Cave in 2000 and 2010.
The molars are distinctly larger
and flatter than anything seen in Modern Humans or Neanderthals, more similar
to those seen in Pliocene Hominids. Only two comparable teeth have been found
at Late Pleistocene sites elsewhere, one from Romania and one from Uzbekistan.
Both are heavily worn, and were most likely third molars.
Occlusal surfaces of the Denisova 4 and Denisova 8 molars and third
molars of a Neandertal and a present-day European. Sawyer & Renaud (2015).
Radiocarbon dating of the layers
from which the teeth were recovered suggests that they were deposited more than
50 000 years ago and about 48 600 years ago. A molecular clock approach (which
measures the rate of mutation on non-sequencing DNA), suggests that the oldest
individual may have lived as long as 60 000 years before the youngest. This
suggests that Denisovans were in the area and using the cave for a considerable
period of time, possibly intermittently with the cave being inhabited by
Neanderthals at other times.
Genetic comparison placed the
teeth in a group along with the fingerbone, suggesting that the Denisovans do
form a separate population, distinct from either Neanderthals or Modern Humans.
However the study showed more genetic diversity among the three Denisovan
individuals (who were all buried in the same cave) than among all known
Neanderthals sequenced (who come from a large area of Europe and West Asia),
though this diversity was still considerably lower than found in modern
Europeans.
The study again found the
Denisovans shared more genetic material with Neanderthals than Modern Humans,
but that this was probably the result of interbreeding, with the ancestors of
the Denisovans having diverged from the common ancestor of Neanderthals and
Modern Humans long before these two groups split, and all Modern Humans having
shared a common ancestor more recently than the split with Neanderthals.
See also...
Neanderthal DNA from a 37 000-42 000 modern Human jaw from Romania. Neanderthals first appeared in
Europe around 300 000 years ago and were replaced by anatomically modern Humans
between 45 000 and 35 000 years ago. Genetic studies if modern Human
populations show that almost all non-Africans have traces of Neanderthal...
Rainforest resources in the diet of Late Pleistocene Humans from Sri Lanka. Early modern Humans expanded from
Africa around the globe in the Late Pleistocene, from about 125 000 years ago
onwards. In doing so they adapted to a wide variety of environments, though
some habitats...
Hominin teeth from the Middle Pleistocene of Anhui Province, China. In the 1970s and 1980s a collection of Hominin bones and teeth were
unearthed in the Longtan Cave at Hexian in Anhui Province in eastern China. The
bones of these remains have been extensively studied, and assigned to the
species Homo erectus, though...
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See also...
Neanderthal DNA from a 37 000-42 000 modern Human jaw from Romania. Neanderthals first appeared in
Europe around 300 000 years ago and were replaced by anatomically modern Humans
between 45 000 and 35 000 years ago. Genetic studies if modern Human
populations show that almost all non-Africans have traces of Neanderthal...Rainforest resources in the diet of Late Pleistocene Humans from Sri Lanka. Early modern Humans expanded from
Africa around the globe in the Late Pleistocene, from about 125 000 years ago
onwards. In doing so they adapted to a wide variety of environments, though
some habitats...Hominin teeth from the Middle Pleistocene of Anhui Province, China. In the 1970s and 1980s a collection of Hominin bones and teeth were
unearthed in the Longtan Cave at Hexian in Anhui Province in eastern China. The
bones of these remains have been extensively studied, and assigned to the
species Homo erectus, though...Follow Sciency Thoughts on Facebook.
