* Astronomy

  Palaeontologists discover most primitive primate skeleton
The origins and earliest branches of primate evolution are clearer and more ancient by 10 million years than previous studies estimated, according to a study featured on the cover of the Jan. 23 print edition of the Proceedings of the National Academy of Sciences.
The paper by researchers at Yale, the University of Winnipeg, Stony Brook University, and led by University of Florida palaeontologist Jonathan Bloch reconstructs the base of the primate family tree by comparing skeletal and fossil specimens representing more than 85 modern and extinct species. The team also discovered two 56-million-year-old fossils, including the most primitive primate skeleton ever described.

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The origins and earliest branches of primate evolution are clearer and more ancient by 10 million years than previous studies estimated, according to a study featured on the cover of the Jan. 23 print edition of the Proceedings of the National Academy of Sciences.
The paper by researchers at Yale, the University of Winnipeg, Stony Brook University, and led by University of Florida palaeontologist Jonathan Bloch reconstructs the base of the primate family tree by comparing skeletal and fossil specimens representing more than 85 modern and extinct species. The team also discovered two 56-million-year-old fossils, including the most primitive primate skeleton ever described.
In the two-part study, an extensive evaluation of skeletal structures provides evidence that plesiadapiforms, a group of archaic mammals once thought to be more closely related to flying lemurs, are the most primitive primates. The team analysed 173 characteristics of modern primates, tree shrews, flying lemurs with plesiadapiform skeletons to determine their evolutionary relationships. High-resolution CT scanning made fine resolution of inaccessible structures inside the skulls possible.

At least five major features characterise modern primates: relatively large brains, enhanced vision and eyes that face forward, a specialised ability to leap, nails instead of claws on at least the first toes, and specialized grasping hands and feet. Plesiadapiforms have some but not all of these traits. The article argues that these early primates may have acquired the traits over 10 million years in incremental changes to exploit their environment.
While the study did not include a molecular evaluation of the samples, according to Sargis, these results are consistent with molecular studies on related living groups. Compatibility with the independent molecular data increases the researchers' confidence in their own results.
Bloch discovered the new plesiadapiform species, Ignacius clarkforkensis and Dryomomys szalayi, just outside Yellowstone National Park in the Bighorn Basin with co-author Doug Boyer, a graduate student in anatomical sciences at Stony Brook. Previously, based only on skulls and isolated bones, scientists proposed that Ignacius was not an archaic primate, but instead a gliding mammal related to flying lemurs. However, analysis of a more complete and well-preserved skeleton by Bloch and his team altered this idea.

"These fossil finds from Wyoming show that our earliest primate ancestors were the size of a mouse, ate fruit and lived in the trees. It is remarkable to think we are still discovering new fossil species in an area studied by palaeontologists for over 100 years" - study leader Jonathan Bloch, a vertebrate palaeontology curator at the Florida Museum of Natural History.

Researchers previously hypothesised plesiadapiforms as the ancestors of modern primates, but the idea generated strong debate within the primatology community. This study places the origins of Plesiadapiforms in the Palaeocene, about 65 (million) to 55 million years ago in the period between the extinction of the dinosaurs and the first appearance of a number of undisputed members of the modern orders of mammals.

Source Yale University

-- Edited by Blobrana at 00:57, 2007-01-24

Humans continued to evolve significantly long after they were established in Europe, and interbred with Neanderthals as they settled across the continent, according to new research published this week in the Proceedings of the National Academy of Sciences (PNAS) USA.
Professor Joao Zilhao of the University of Bristol, Professor Erik Trinkaus of Washington University and colleagues in Europe compared the features of an early modern human cranium found in the Peştera cu Oase (the Cave with Bones) in southwestern Romania with other human samples from the period (the Late Pleistocene).  Differences between the skulls suggest complex population dynamics as modern humans dispersed into Europe.
The different fragments of the reconstructed cranium – named Oase 2 – were found in a Late Pleistocene bone bed principally containing the remains of cave bears.  They were recovered during a systematic excavation project directed by Professor Trinkaus and Professor Zilhao between 2003 and 2005.
Radiocarbon dating of the specimen produced only a minimum age (more than 35,000 years), but similarity in morphological traits with the Oase 1 human mandible – found in 2002 on the surface of the cave, adjacent to the excavation area, and dated to about 40,500 years ago – lead the team to conclude that the two fossils were the same age.  These are the earliest modern human remains so far found in Europe and represent our best evidence of what the modern humans who first dispersed into Europe looked like.
By comparing it with other skulls, Professor Zilhao and colleagues found that  Oase 2 had the same proportions as modern human crania and shared a number of modern human and/or non-Neanderthal features.
However, there were some important differences: apparently independent features that are, at best, unusual for a modern human.  These included frontal flattening, a fairly large juxtamastoid eminence and exceptionally large upper molars with unusual size progression which are found principally among the Neanderthals.

“Such differences raise important questions about the evolutionary history of modern humans.  They could be the result of evolutionary reversal or reflect incomplete palaeontological sampling of Middle Palaeolithic human diversity. They could also reflect admixture with Neanderthal populations as modern humans spread through western Eurasia.  This mixture would have resulted in both archaic traits retained from the Neanderthals and unique combinations of traits resulting from the blending of previously divergent gene pools. The ultimate resolution of these issues must await considerations of larger samples of European early modern humans and chronologically intervening specimens.  But this fossil is a major addition to the growing body of fossil, genetic and archaeological evidence indicating significant levels of biological and cultural interaction between modern humans and the anatomically archaic populations (including the Neanderthals) they met along the way as they spread from Africa into Eurasia”  - Professor Zilhao.

It is apparent that the Oase 2 cranium indicates there was significant modern human morphological evolution since the early Upper Palaeolithic, the researchers conclude.  Oase 2 is ‘modern’ in its abundance of derived modern human features, but it remains ‘non-modern’ in its complex constellation of archaic and modern features.

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Timor cave may reveal how humans reached Australia
An archaeologist has discovered the oldest evidence of occupation by modern humans on the islands that were the stepping stones from South-East Asia to Australia. A cave site in East Timor where people lived more than 42,000 years ago, eating turtles, tuna and giant rats, was unearthed by Sue O'Connor, head of archaeology and natural history at the Australian National University. Dr O'Connor also found ancient stone tools and shells used for decoration in the limestone shelter, known as Jerimalai, on the eastern tip of the island.
Her discovery could help solve the mystery of the route ancient seafarers took to get here from South-East Asia. It strengthens the view that they made a southern passage, via Timor, rather than travelling northwards via Borneo and Sulawesi, then down through Papua New Guinea.
Sea levels were lower when modern humans set off around the coast from Africa more than 70,000 years ago. People who made it to the large South-East Asian land mass known as Sunda, however, still had to cross deep ocean channels to get to Australia, then joined to Papua New Guinea in a continent called Sahul. Until now, the age of habitation sites found on the stepping stone islands in between had been much younger than those found in Australia, making it impossible to determine the route taken.
Although the Jerimalai site is at least 42,000 years old, it could be much older, because this was the detection limit of the radiocarbon dating method used. The simple stone tools unearthed in the shelter were similar to those used by the species of hobbit-sized people who lived in a cave on the nearby island of Flores until 12,000 years ago. Dr O'Connor is confident Jerimalai's inhabitants were modern humans, Homo sapiens, and not small-brained members of Homo floresiensis, because of the evidence for their sophisticated behaviour found in the dig. Fish such as tuna, for example, "could only have been captured in the deeper waters offshore using hooks, and probably also water craft".

The find, however, raised big questions, such as why modern humans appeared to have bypassed Flores on their way to Timor. One possibility was that the hobbits were able to repel them.

"It is clear that this region warrants a great deal more study" - Dr O'Connor.

Source: The Sydney Morning Herald