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http://www.sciencedaily.com/releases/2013/05/
130515131556.htm
Oldest Evidence of Split Between Old World Monkeys and Apes: Primate Fossils
Are 25 Million Years Old
May 15, 2013 â" Two fossil discoveries from the East African Rift reveal new
information about the evolution of primates, according to a study published
online in Nature this week led by Ohio University scientists.
The team's findings document the oldest fossils of two major groups of
primates: the group that today includes apes and humans (hominoids), and the
group that includes Old World monkeys such as baboons and macaques
(cercopithecoids).
Geological analyses of the study site indicate that the finds are 25 million
years old, significantly older than fossils previously documented for either of
the two groups.
Both primates are new to science, and were collected from a single fossil site
in the Rukwa Rift Basin of Tanzania. Rukwapithecus fleaglei is an early
hominoid represented by a mandible preserving several teeth. Nsungwepithecus
gunnelli is an early cercopithecoid represented by a tooth and jaw fragment.
The primates lived during the Oligocene epoch, which lasted from 34 to 23
million years ago. For the first time, the study documents that the two
lineages were already evolving separately during this geological period.
"The late Oligocene is among the least sampled intervals in primate
evolutionary history, and the Rukwa field area provides a first glimpse of the
animals that were alive at that time from Africa south of the equator," said
Nancy Stevens, an associate professor of paleontology in Ohio University's
Heritage College of Osteopathic Medicine who leads the paleontological team.
Documenting the early evolutionary history of these groups has been elusive, as
there are few fossil-bearing deposits of the appropriate age, Stevens
explained. Using an approach that dated multiple minerals contained within the
rocks, team geologists could determine a precise age for the specimens.
"The rift setting provides an advantage in that it preserves datable materials
together with these important primate fossils," said lead geologist Eric
Roberts of James Cook University in Australia.
Prior to these finds, the oldest fossil representatives of the hominoid and
cercopithecoid lineages were recorded from the early Miocene, at sites dating
millions of years younger.
The new discoveries are particularly important for helping to reconcile a
long-standing disagreement between divergence time estimates derived from
analyses of DNA sequences from living primates and those suggested by the
primate fossil record, Stevens said. Studies of clock-like mutations in primate
DNA have indicated that the split between apes and Old
World monkeys occurred between 30 million and 25 million years ago.
"Fossils from the Rukwa Rift Basin in southwestern Tanzania provide the first
real test of the hypothesis that these groups diverged so early, by revealing a
novel glimpse into this late Oligocene terrestrial ecosystem," Stevens said.
The new fossils are the first primate discoveries from this precise location
within the Rukwa deposits, and two of only a handful of known primate species
from the entire late Oligocene, globally.
The scientists scanned the specimens in the Ohio University's MicroCT scanner,
allowing them to create detailed 3-dimensional reconstructions of the ancient
specimens that were used for comparisons with other fossils.
"This is another great example that underscores how modern imaging and
computational approaches allow us to address more refined questions about
vertebrate evolutionary history," said Patrick O'Connor, co-author and
professor of anatomy in Ohio University's Heritage College of Osteopathic
Medicine.
In addition to the new primates, Rukwa field sites have produced several other
fossil vertebrate and invertebrate species new to science. The late Oligocene
interval is interesting because it provides a final snapshot of the unique
species inhabiting Africa prior to large-scale faunal exchange with Eurasia
that occurred later in the Cenozoic Era, Stevens said.
A key aspect of the Rukwa Rift Basin project is the interdisciplinary nature of
the research team, with paleontologists and geologists working together to
reconstruct vertebrate evolutionary history in the context of the developing
East African Rift System.
"Since its inception this project has employed a multifaceted approach for
addressing a series of large-scale biological and geological questions centered
on the East African Rift System in Tanzania," O'Connor said.
The team's research, funded by the U.S. National Science Foundation, the Leakey
Foundation and the National Geographic Society, underscores the integration of
paleontological and geological approaches that are essential for addressing
complex issues in vertebrate evolutionary history, the scientists noted.
Co-authors on the study are Patrick O'Connor, Cornelia Krause and Eric Gorscak
of Ohio University, Erik Seiffert of SUNY Stony Brook University, Eric Roberts
of James Cook University in Australia, Mark Schmitz of Boise State University,
Sifa Ngasala of Michigan State University, Tobin Hieronymus of Northeast Ohio
Medical University and Joseph Temu of the Tanzania Antiquities Unit.
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Story Source:
The above story is reprinted from materials provided by Ohio University.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
Nancy J. Stevens, Erik R. Seiffert, Patrick M. OâConnor, Eric M. Roberts,
Mark D. Schmitz, Cornelia Krause, Eric Gorscak, Sifa Ngasala, Tobin L.
Hieronymus, Joseph Temu. Palaeontological evidence for an Oligocene divergence
between Old World monkeys and apes. Nature, 2013; DOI: 10.1038/nature12161
Need to cite this story in your essay, paper, or report? Use one of the
following formats:
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Ohio University (2013, May 15). Oldest evidence of split between Old World
monkeys and apes: Primate fossils are 25 million years old. ScienceDaily.
Retrieved May 16, 2013, from http://www.sciencedaily.comÂ
/releases/2013/05/130515131556.htm
Note: If no author is given, the source is cited instead.
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