Last Common Ancestor lived in Africa 10-11 mya

source: http://www.nature.com/news/2007/070820/pf/448844a_pf.html

The last common ancestor of humans and gorillas might have lived at
least 2 million years earlier than previously thought. Fossilized
teeth of the earliest gorilla ever discovered, dating to 10 million
years ago, have been found in Africa, say researchers.

The new species (Chororapithecus abyssinicus) from Ethiopia, reported
on 'A new species of great ape from the late Miocene epoch in
Ethiopia' of this issue, helps to fill in a huge gap in the fossil
record. The team of Ethiopian and Japanese researchers has based its
conclusion on just nine teeth from at least three individuals of the
species, which were discovered in the desert scrubland of Afar about
170 kilometres east of Addis Ababa.

The teeth, eight molars and a canine, "are collectively
indistinguishable from modern gorilla subspecies" in size, proportion
and scan-revealed internal structure, says Gen Suwa of the University
of Tokyo Museum, Japan, who led the study. The team argues that the
gorilla's divergence date from the human lineage is not about 8
million years ago as previously surmised (S. Kumar et al. Proc. Natl
Acad. Sci. USA102, 18842-18847; 2005), but "greater than 10 to 11
million years ago" on the basis of the age of the new species.
Functionally, he adds, the teeth already seem to be evolving - they
could shear through a plant diet, a gorilla trait - although other
herbivore apes also exist in the fossil record.

Africa was the place of origin of both humans and modern African
apes.

This finding could prompt discussions of how anthropologists and
geneticists determine the hominin line's divergence from chimps,
previously pegged at about 6 million years ago. "Chororapithecus
abyssinicus suggests, once again, that Africa was the place of origin
of both humans and modern African apes" - not Eurasia as some
researchers have argued, says Suwa.

But palaeoanthropologist Jay Kelley, who studies primate teeth at the
University of Illinois at Chicago and was not involved in the study,
is sceptical. "I'm not convinced it is a gorilla," he says. More
fossils, analysis and debate will be needed to determine whether the
specimen is ancestral to hominids, he adds. For now, he would be "very
cautious" about using the specimen to realign divergence dates between
hominins and gorillas-chimps.

Suwa's team is part of the Revealing Human Origins Initiative (RHOI),
a project that searches at multiple sites in Africa, Europe and Asia
for species that predate the earliest known hominid, the 7-million-
year-old Sahelanthropus tchadensis (M. Brunet et al. Nature 418, 145-
151; 2002).

Between 15 million and 22 million years ago, there were dozens of
primate species across Africa and Euroasia - and apes dominated the
primate scene. But fossils show that these species don't share the
characteristics of modern African apes. "From that species pool, the
common ancestor of African apes and humans branched out," says Tim
White, a palaeoanthropologist at the University of California,
Berkeley, and an RHOI director. "And the goal of RHOI is to find the
common ancestors. With C. abyssinicus, we now can see an ancestral
African ape."
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source: http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2007/08/22/MN2DRM49O.DTL&type=printable

Fossil hunters tracing the long and tangled paths of evolution in
Africa have discovered the remains of ancient apes, much like modern
gorillas, that suggest a human lineage stretching back as far as 20
million years, when creatures like orangutans were among our earliest
ancestors.

Led by two anthropologists who were graduate students at UC Berkeley
more than 20 years ago, the team has found a collection of nine fossil
teeth plucked from the hardscrabble dirt and rocks on the flanks of an
old volcanic gorge in southern Ethiopia. Those teeth, they say,
provide the best clues yet to determine the times when the common
ancestors of great apes and humans first emerged in Africa.

Gen Suwa, now an anthropology professor at the University of Tokyo,
and Berhane Asfaw, now director of the Rift Valley Research Service in
Ethiopia, led an expedition two years ago to the remote fossil area
100 miles east of Addis Ababa, the Ethiopian capital, and returned
again in March with Yonas Beyene, an Ethiopian archaeologist.

Their harvest on that first venture was only a single somewhat worn
and very ancient canine tooth that appeared to have come from a female
ape or a very young male, but when they returned this year, the team's
sharp-eyed Ethiopian hunters found eight molars incised with patterns
that clearly bespoke their gorilla origins - well adapted to crush and
chew tough, fibrous foliage - the very diet of today's gorillas. The
teeth may have come from at least three and probably six or more
individuals, the scientists inferred.

Modern geneticists have sought to establish "molecular clocks" for the
evolution of humanity's forebears, based on the rates at which genes
are presumed to mutate. But to Suwa and Asfaw and their colleagues,
those clocks could well be millions of years off - and the fossils
show dates much earlier than the molecular estimates, they say.

Their findings also indicate that the ape-to-human lineage must have
had its earliest beginnings right there in southern Ethiopia, and not
in Europe or Asia as some earlier Eurasian fossil finds have suggested
from discoveries in Spain, India and Pakistan.

The team's report on the newfound fossils is being published today in
the journal Nature.

"The report is one of the most important" on the issues, and "opens a
window on the timing of evolution that we've never had before. This
implies that the common ancestor of chimps and humans is much earlier
than is currently claimed by geneticists," said C. Owen Lovejoy, an
anthropologist and anatomist at Kent State University who was not
connected with the research team.

The scientists have named their large ape Chororapithecus abyssinicus
after Chorora, a southern Ethiopian village and its surrounding
geological formation where the teeth were found. Pithecus is Greek for
ape and Abyssinia is the historic name for Ethiopia.

It took 60 miles of hiking across dry patches of ancient lava and
sedimentary rocks with few shrubs before the first fossil was found -
what Asfaw called "something new - Ethiopia's first fossil great ape."

And it took the most modern three-dimensional X-ray equipment, called
micro-computed tomography, in Suwa's Tokyo laboratory to reveal the
structure of the molars and establish that they were indeed from some
kind of "proto-gorilla" and "shared with modern gorillas some unique
specialization for eating fibrous foodstuff such as stems and leaves,"
as Suwa said in an e-mail description of the team's discovery.

The region is about 120 miles south of Ethiopia's Middle Awash region
in the Afar desert that has yielded fossils of early human-like
creatures nearly 6 million years old, and 160 miles south of Hadar,
the famed site where the 3.2 million-year-old bones of Lucy were
found.

It now is dry, harsh and filled with lava patches that remain from a
time when what is now the continent of Africa was split apart by
violent tectonic forces to create its Great Rift Valley many millions
of years ago. But when those apes and their orangutan ancestors were
alive, the area must have been braided with rivers, lakes and forests,
the scientists say.

Among the 330 fragments of fossil bones and teeth that the team found
were the remains of many other ancestral animals, including early
versions of elephants, rhinos, horses, hippos, swine, giraffes, and
cloven-hoofed beasts like cows, bison and antelopes.

From dates established by the decay rates of radio isotopes in the
surrounding volcanic ash, the scientists estimate that the gorilla
lineage must have evolved from a common ancestor of orangutans about
20 million years ago, that gorillas and chimpanzees then split from
some earlier common ancestors about 12 million years ago, and that the
last common ancestor of chimps and hominids - the first creatures in
the human lineage - must have lived about 9 million years ago.

Suwa and Asfaw both began their careers at UC Berkeley, where they
earned their doctorates working with the late anthropologists J.
Desmond Clark and F. Clark Howell, and with Tim D. White, now a
leading paleoanthropologist who has long worked in Ethiopia's Middle
Awash region.

Said White commenting on the new report: "These fossils appear to
represent the dawn of the gorilla lineage 10 million years ago. They
shed much-needed light on the evolutionary history of modern gorillas
and our own ancestry - ironically just as the magnificent gorillas now
face extinction.

"Before this discovery, the lack of African fossils prompted some
paleontologists to conclude that our common ancestor with African apes
must have immigrated from Eurasia. Ethiopia's Chorora fossils now
begin to fill this gap in the evolutionary record, showing that there
are still many things to learn about Africa's deep past."
_____________________________

source: http://www.livescience.com/animals/070822_new_ape.html

Recently unearthed fossils belonging to a new ape species suggest the
lineages leading to humans and gorillas split several million years
earlier than previously thought.

Found in Ethiopia, the 10 million-year-old fossilized teeth resemble
those of modern gorillas and appear specialized for eating fibrous
foods such as stems and leaves.

"If it's not a gorilla relative, then it's something very similar to
what an early gorilla must have looked like," said study leader Gen
Suwa, a paleoanthropologist at the University of Tokyo.

Dubbed Chororapithecus abyssinicus, the new species is the oldest
primate known to be directly related to living African gorillas.

The finding, detailed in the Aug. 23 issue of the journal Nature,
suggests humans and gorillas last shared a common ancestor at least 10
million years ago. It could also push back the time when the lineages
of humans and chimpanzees split.

Recalibrating the molecular clock

Most molecular studies have concluded that humans and gorillas
diverged by about 8 million years ago, and that humans and chimpanzees
split some 5 to 6 million years ago. However, these conclusions were
based on the assumption that the lineages leading to humans and
orangutans split about 15 million years ago.

Since each "tree branch" is placed on the evolutionary tree in
relation to the other branches, the time scale is relative, making the
human-orangutan split critical to the timing of other changes.

"The molecular data themselves do not provide ages on the branches of
the lineages. You have to calibrate the molecular distances, so it's
kind of like a relative scale," said Tim White, an anthropologist at
the University of California, Berkeley, who was not involved in the
study.

The new fossils could potentially serve as even better calibrators for
the molecular scale than the current orangutan ancestor specimen.

"If it is accepted by paleontologists that this is indeed a fossil
which is very close to the split of humans and gorillas, then it would
become a very useful calibration point to [look] backwards in time,
towards orangutans, and also forward in time" toward the human and
chimpanzee split, said Sudhir Kumar, a researcher at Arizona State
University whose genetic analyses have helped determine the time of
the human-chimp split.

However, scientists will first have to determine if Chororapithecus
lived after the gorilla lineage split from that of humans and chimps,
or if it lived right before that point.

"Unless that question is answered, it is very hard to place whether
these fossils are telling us about the gorilla-human divergence, or
about the divergence of the ancestors of humans and gorillas from
orangutans," said Kumar, who was involved in the study. "That question
is not answered yet."

The original motherland

The new discovery also supports the idea that, like humans, gorillas
and chimpanzees have primary roots in Africa, and not in Europe or
Asia, as others have suggested.

"Chororapithecus suggests, once again, that Africa was the place of
origin of both humans and modern African apes," the authors said in a
prepared statement.

The new fossils also help anthropologists with a data problem, White
said.

"So many people have been saying there's a gap in the African fossil
record [from that time], and these fossils begin to fill that gap,"
White told LiveScience.

Even though the fossil record of human evolution is still patchy, it
is much better than that of the great apes. Very few fossils have
surfaced for gorilla evolution for the past 6 million years, and the
first ever chimpanzee fossil was found only in 2005.

"The human fossil line is really quite well-known between 6 million
years ago and today," White said. "It's basically a black hole when it
comes to fossils of the African apes themselves."
_____________________________

source: http://www.primates.com/pierolapithecus/index.html

Scientists in Spain have discovered fossils of an ape species from
about 13 million years ago that they think may have been the last
common ancestor of all living great apes, including humans.

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