Showing posts with label extinction. Show all posts
Showing posts with label extinction. Show all posts

Friday, 11 November 2011

Hi-tech scans catch prehistoric mite hitching ride on spider


Hi-tech scans catch prehistoric mite hitching ride on spider

09 Nov 2011

Scientists have produced amazing three-dimensional images of a prehistoric mite as it hitched a ride on the back of a 50 million-year-old spider.

At just 176 micrometres long and barely visible to the naked eye, University of Manchester researchers and colleagues in Berlin believe the mite, trapped inside Baltic amber (fossil tree resin), is the smallest arthropod fossil ever to be scanned using X-ray computed tomography (CT) scanning techniques.
They say their study – published in the Royal Society journal Biology Letters today (Wednesday, 9 November) – also sets a minimum age of almost 50 million years for the evolution among these mites of phoretic, or hitchhiking, behaviour using another animal species.
“CT allowed us to digitally dissect the mite off the spider in order to reveal the important features on the underside of the mite required for identification,” said Dr David Penney, one of the study’s authors based in the Faculty of Life Sciences. “The specimen, which is extremely rare in the fossil record, is potentially the oldest record of the living family Histiostomatidae.
“Amber is a remarkable repository of ecological associations within the fossil record. In many cases organisms died instantaneously and were preserved with lifelike fidelity, still enacting their behaviour immediately prior to their unexpected demise. We often refer to this as 'frozen behaviour' or palaeoethology and such examples can tell us a great deal about interactions in ecosystems of the past. However, most amber fossils consist of individual insects or several insects together but without unequivocal demonstrable evidence of direct interaction. The remarkable specimen we describe in this paper is the kind of find that occurs only once in say a hundred thousand specimens.”


Fellow Manchester biologist Dr Richard Preziosi said: “Phoresy is where one organism uses another animal of a different species for transportation to a new environment. Such behaviour is common in several different groups today. The study of fossils such as the one we described can provide important clues as to how far back in geological time such behaviours evolved. The fact that we now have technology that was unavailable just a few years ago means we can now use a multidisciplinary approach to extract the most information possible from such tiny and awkwardly positioned fossils, which previously would have yielded little or no substantial scientific data.”
Co-author Professor Phil Withers, from Manchester’s School of Materials, said: “We believe this to be the smallest amber inclusion scanned anywhere to date. With our sub-micron phase contrast system we can obtain fantastic 3D images and compete with synchrotron x-ray systems and are revealing fossils previously inaccessible to imaging. With our nanoCT lab systems, we are now looking to push the boundaries of this technique yet further.”
Dr Jason Dunlop, from the Humboldt University, Berlin, added: "As everyone knows, mites are usually very small animals, and even living ones are difficult to work with. Fossil mites are especially rare and the particular group to which this remarkable new amber specimen belongs has only been found a handful of times in the fossil record. Yet thanks to these new techniques, we could identify numerous important features as if we were looking at a modern animal under the scanning electron microscope. Work like this is breaking down the barriers between palaeontology and zoology even further."
Ends

Tuesday, 1 November 2011

Archaeopteryx and the dinosaur-bird family tree 14 September 2011


Archaeopteryx and the dinosaur-bird family tree

14 September 2011

The magpie-sized Archaeopteryx had bird and dinosaur features and helped show that birds evolved from dinosaurs. However, recent research in the journal Nature questions its position in the dinosaur-bird family tree.
Scientists know birds evolved from dinosaurs because many fossils have been found of ancient animals with both bird and dinosaur features, including the famousArchaeopteryx that lived 147 million years ago.
Painting of how Archaeopteryx may have looked
Painting of how Archaeopteryxmay have looked 147 million years ago © John Sibbick / Natural History Museum
Archaeopteryx had a feathered tail and wings with a flight feather arrangement just like modern birds. But it also had a long bony tail, teeth, and 3 fingers ending in claws, like dinosaurs. 
The first Archaeopteryx skeleton fossil was uncovered in 1861 in Solnhofen, Germany, and is looked after at the Natural History Museum. It provided the first evidence that helped demonstrate that modern birds descended from small meat-eating dinosaurs.
Along with researchers from all over the world, Museum scientists have studied the specimen ever since, and they have been able to reveal that it had hearing like an emu and a brain like a chicken.
Still a bird?
Close up of Museum Archaeopteryx specimen showing the bird characteristic of a reversed perching toe
Close up of MuseumArchaeopteryx specimen showing the bird characteristic of a reversed perching toe. 
No other fossils of bird-like creatures older thanArchaeopteryx were known at the time, or for most of the time since this early discovery. So it became established as the earliest known bird. But is this still so?
Since the discovery of Archaeopteryx, many more fossils with combined dinosaur and bird features have been uncovered, especially in the last 10 years (with only 9 other Archaeopteryxfinds over the last 150 years).
In June, scientists revealed a new species from China that they say shows Archaeopteryx was not a bird at all.
Xing Xu from the Institute of Vertebrate Paleontology and Paleoanthropology, in Beijing, and colleagues, identified the feathered and chicken-sized Xiaotingia zhengi. It was very similar to Archaeopteryx, sharing features such as long and robust forelimbs, which the team says puts them together in the dinosaur group rather than with birds.
Fossil tail of 147-million-year-old Archaeopteryx shows bird-like feather
Museum specimen showing the fossil tail of 147-million-year-oldArchaeopteryx that shows the bird-like feather and dinosaur-like long bony tail.
Dr Paul Barrett, Museum dinosaur expertsays, ‘The June research shows just how fine the line between birds and non-avian dinosaurs really is’.
Species that have a mixture of features, and are hard to place in one group or another, are known as transitional forms, sometimes incorrectly called a ‘missing link’. Their fossils provide a record of significant steps in the evolution of new features.
Although Archaeopteryx and X. zhengi had some bird-like features, the researchers say they had more features that put them in the group Deinonychosauria, which includesMicroraptor and Velociraptor, rather than in the bird group Avialae.
So, does the whole bird family tree need re-arranging? 
Not according to Barrett. ‘Xiaotingia does not necessitate a major re-writing of early bird evolution, but shows that the evolution of many of the detailed anatomical features that changed during the origin of birds may have been slightly more complex than previously thought.’
Dr Angela Milner, Museum dinosaur expertcomments. ‘This recent research in no way diminishes the scientific and historical importance of Archaeopteryx.
‘Thomas Henry Huxley [pioneering biologist and educator] pointed out in 1868 that it was the first fossil to provide a snapshot of evolution in action between two major groups, dinosaurs and birds, and a clear demonstration that birds are the descendents of small meat-eating dinosaurs.
Another bird-like branch?
If Archaeopteryx is not a direct ancestor of birds, why does it have bird-like features and where does it sit in relation to the transition of dinosaurs to birds?
Archaeopteryx could be on another branch of the dinosaur family tree with bird-like feathers and skeletal features evolving in another closely related dinosaur group, suggests Barrett.
‘Maybe Archaeopteryx wasn't on the direct ancestral line to birds, but was part of an early experimentation in how to build a bird-like body.’
Overall bird origin picture
The overall picture of birds descending from meat-eating dinosaurs is firmly established. Now scientists need to rearrange the details of the early stages in the bird evolutionary tree.
Barrett adds, ‘As the authors of the June paper note, the evidence suggesting thatArchaeopteryx is not a bird is fairly equivocal and new analyses or new animals could very easily change this picture.
‘In reality what we now have are a set of animals incredibly close to bird origin – unsurprisingly these are very similar to each other, to birds and to other small meat-eating dinosaurs. As they are so similar, it becomes exceptionally difficult to disentangle their relationships accurately.’
Milner concludes, ‘The fact that Archaeopteryx may represent one of many early flying experiments rather than being the direct ancestor of modern birds is no surprise at all.
‘It is only now that Archaeopteryx can be assessed in the context of all the recent discoveries in China which provide so much more information.

Saturday, 22 October 2011

An ancient bone with a projectile point lodged within it appears to up-end - once and for all - a long-held idea of how the Americas were first popula

Old American theory is 'speared'

Bone It would have taken a lot of force to drive the point into the mastodon bone

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An ancient bone with a projectile point lodged within it appears to up-end - once and for all - a long-held idea of how the Americas were first populated.
The rib, from a tusked beast known as a mastodon, has been dated precisely to 13,800 years ago.
This places it before the so-called Clovis hunters, who many academics had argued were the North American continent's original inhabitants.
News of the dating results is reported in Science magazine.
In truth, the "Clovis first" model, which holds to the idea that America's original human population swept across a land-bridge from Siberia some 13,000 years ago, has looked untenable for some time.
A succession of archaeological finds right across the United States and northern Mexico have indicated there was human activity much earlier than this - perhaps as early as 15-16,000 years ago.
The mastodon rib, however, really leaves the once cherished model with nowhere to go.
The specimen has actually been known about for more than 30 years. It is plainly from an old male animal that had been attacked with some kind of weaponry.
It was found in the late 1970s at the Manis site near Sequim, north-west of Seattle, in Washington State.
Although scientists at the time correctly identified the specimen's antiquity, adherents to the Clovis-first model questioned the dating and interpretation of the site.
To try to settle any lingering uncertainty, Prof Michael Waters of Texas A&M University and colleagues called upon a range of up-to-date analytical tools and revisited the specimen.
These investigations included new radio carbon tests using atomic accelerators.
"The beauty of atomic accelerators is that you can date very small samples and also very chemically pure samples," Prof Waters told BBC News.
"We extracted specific amino acids from the collagen in the bone and dated those, and yielded dates 13,800 years ago, plus or minus 20 years. That's very precise." It is 800 years or so before Clovis evidence is seen in the historical record.
Computed tomography, which creates exquisite 3D X-ray images of objects, was used to study the embedded point. The visualisation reveals how the projectile end had been deliberately sharpened to give a needle-like quality. And it also enabled the scientists to estimate the projectile end's likely original size - at least 27cm long, they believe.
"The other thing that's really interesting is that as it went in, the very tip broke and rotated off to the side," said the Texas A&M researcher.
Bone The CT imagery reveals the extent of the wound and the shape of the buried point's end
"That's a very common breakage pattern when any kind of projectile hits bone. You see it even in stone projectiles that are embedded in, say, bison bones."
DNA investigation also threw up a remarkable irony - the point itself was made from mastodon bone, proving that the people who fashioned it were systematically hunting or scavenging animal bones to make their tools.
The timing of humanity's presence in North America is important because it plays into the debate over why so many great beasts from the end of the last Ice Age in that quarter of the globe went extinct.
Not just mastodons, but woolly mammoths, sabre-toothed cats, giant sloths, camels, and teratorns (predatory birds with a nearly four-metre wingspan) - all disappeared in short order a little over 12,700 years ago.
A rapidly changing climate in North America is assumed to have played a key role - as is the sophisticated stone-tool weaponry used by the Clovis hunters. But the fact that there are also humans with effective bone and antler killing technologies present in North America deeper in time suggests the hunting pressure on these animals may have been even greater than previously thought.
"Humans clearly had a role in these extinctions and by the time the Clovis technology turns up at 13,000 years ago - that's the end. They finished them off," said Prof Waters.
"You know, the Clovis-first model has been dying for some time," he finished. "But there's nothing harder to change than a paradigm, than long-standing thinking. When Clovis-First was first proposed, it was a very elegant model but it's time to move on, and most of the archaeological community is doing just that."
Mastodon Now extinct, the mastodon was a large elephant-like animal


Wednesday, 10 August 2011

Giant fossil shows huge birds lived among dinosaurs

Giant fossil shows huge birds lived among dinosaurs

Lower jaw of S. nessovi (Naish/Dyke/Cau/Escuillié/Godefroit) The fossilised jawbone is nearly twice the length of that of an ostrich, the largest bird found on Earth today

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An enormous jawbone found in Kazakhstan is further evidence that giant birds roamed - or flew above - the Earth at the same time as the dinosaurs.

Writing in Biology Letters, researchers say the new species, Samrukia nessovi, had a skull some 30cm long.

If flightless, the bird would have been 2-3m tall; if it flew, it may have had a wingspan of 4m.

The find is only the second bird of such a size in the Cretaceous geologic period, and the first in Asia.

The only other evidence of a bird of such a size during the period was a fossilised spinal bone found in France and reported in a 1995 paper in Nature.

Sharing space

An overwhelming majority of the birds known from the period would have been about crow-sized, but Dr Darren Naish of the University of Portsmouth said that a second find of an evidently different species suggests that large birds were common at the time.

"This fossil is only known from its lower jaw, so unfortunately we can't say anything at all with certainty about the shape and form of the whole animal.

"If it was flightless and sort of ostrich-shaped, it would have been maybe 2-3m tall and somewhere over 50kg," he explained to BBC News. "If it was a flying animal, then maybe it was shaped like a big albatross or a condor."

Dr Naish also wondered about the dinosaurs with which the enormous birds shared their space.

"I think the really interesting thing is that they're living alongside the big dinosaurs we know were around at the time: big tyrannosaurs, long-necked sauropods, duck-billed dinosaurs," he said. "That opens up loads of questions about ecological interactions that we can only speculate about.

"People have said there weren't big birds when there were big pterosaurs, but now we know there were."

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Wednesday, 3 August 2011

Ancient primate fossil unearthed

Ancient primate fossil unearthed

Primate fossil The researchers say the skull belongs to a creature called Ugandapithecus major

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Researchers working in Uganda say they have unearthed the well-preserved fossil skull of an ancient primate.

The 20 million-year-old specimen comes from the site of an extinct volcano in Uganda's north-east Karamoja region.

The scientists say preliminary analysis showed the tree-climbing herbivore was roughly 10 years old when it died.

The skull is about the same size as that of a chimp, but its brain was smaller.

"It is a highly important fossil and it will certainly put Uganda on the map in terms of the scientific world," Martin Pickford, a palaeontologist from the College de France in Paris, told journalists in Kampala.

Dr Pickford and his colleague Brigitte Senut say the fossil skull belonged to a creature they call Ugandapithecus major.

Professor Senut, a professor at the French National Museum of Natural History said that the remains would be taken to Paris to be X-rayed and documented before being returned to Uganda.

"It will be cleaned in France, it will be prepared in France... and then in about one year's time it will be returned to the country," she said.

The remote and arid region of Karamoja is one of the least developed in Uganda.

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Saturday, 30 July 2011

Feathers fly in first bird debate


Feathers fly in first bird debate

An artist's impression of the new creature from China. How will it change our view of the origin of birds?

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A chicken-sized dinosaur fossil found in China may have overturned a long-held theory about the origin of birds.

For 150 years, a species called Archaeopteryx has been regarded as the first true bird, representing a major evolutionary step away from dinosaurs.

But the new fossil suggests this creature was just another feathery dinosaur and not the significant link that palaeontologists had believed.

The discovery of Xiaotingia, as it is known, is reported in Nature magazine.

The authors of the report argue that three other species named in the past decade might now be serious contenders for the title of "the oldest bird".

Archaeopteryx has a hallowed place in science, long hailed as not just the first bird but as one of the clearest examples of evolution in action.

Archaeopteryx fossil Wobbling perch: Archaeopteryx is one of the most famous fossils ever unearthed

Discovered in Bavaria in 1861 just two years after the publication of Darwin's Origin of Species, the fossil seemed to blend attributes of both reptiles and birds and was quickly accepted as the "original bird".

But in recent years, doubts have arisen as older fossils with similar bird-like features such as feathers and wishbones and three fingered hands were discovered.

Now, renowned Chinese palaeontologist Professor Xu Xing believes his new discovery has finally knocked Archaeopteryx off its perch.

His team has detailed the discovery of a similar species, Xiaotingia, which dates back 155 million years to the Jurassic Period.

By carefully analysing and comparing the bony bumps and grooves of this new chicken-sized fossil, Prof Xu now believe that both Archaeopteryx and Xiaotingia are in fact feathery dinosaurs and not birds at all.

"There are many, many features that suggest that Xiaotingia and Archaeopteryx are a type of dinosaur called Deinonychosaurs rather than birds. For example, both have a large hole in front of the eye; this big hole is only seen in these species and is not present in any other birds.

New contenders for oldest bird

Epidexipteryx

Several species discovered in the past decade could now become contenders for the title of most basal fossil bird.

Epidexipteryx - a very small feathered dinosaur discovered in China and first reported in 2008 (above). It had four long tail feathers but there is little evidence that it could fly.

Jeholornis - this creature lived 120 million years ago in the Cretaceous. It was a relatively large bird, about the size of a turkey. First discovered in China, and reported in 2002.

Sapeornis - lived 110 to 120 million years ago. Another small primitive bird about 33 centimetres in length. It was discovered in China and was first reported in 2002.

"Archaeopteryx and Xiaotingia are very, very similar to other Deinonychosaurs in having a quite interesting feature - the whole group is categorised by a highly specialised second pedo-digit which is highly extensible, and both Archaeopteryx and Xiaotingia show initial development of this feature."

The origins of the new fossil are a little murky having originally been purchased from a dealer. Prof Xu first saw the specimen at the Shandong Tianyu Museum. He knew right away it was special

"When I visited the museum which houses more than 1,000 feathery dinosaur skeletons, I saw this specimen and immediately recognised that it was something new, very interesting; but I did not expect it would have such a big impact on the origin of birds."

Other scientists agree that the discovery could fundamentally change our understanding of birds. Prof Lawrence Witmer from Ohio University has written a commentary on the finding.

"Since Archaeopteryx was found 150 years ago, it has been the most primitive bird and consequently every theory about the beginnings of birds - how they evolved flight, what their diet was like - were viewed through the lens of Archaeopteryx.

"So, if we don't view birds through this we might have a different set of hypotheses."

There is a great deal of confusion in the field says Prof Witmer as scientists try to understand where dinosaurs end and where birds begin.

"It's kind of a nightmare for those of us trying to understand it. When we go back into the late Jurassic, 150-160 million years ago, all the primitive members of these different species are all very similar.

"So, on the one hand, it's really frustrating trying to tease apart the threads of this evolutionary knot, but it's really a very exciting thing to be working on and taking apart this evolutionary origin."

Skeleton of Xiaotingia zhengi Prof Xu first saw the specimen in a museum. He knew right away it was special

Such are the similarities between these transition species of reptiles and birds that other scientists believe that the new finding certainly will not mean the end of the argument.

Prof Mike Benton from the University of Bristol, UK, agrees that the new fossil is about the closest relative to Archaeopteryx that has yet been found. But he argues that it is far from certain that the new finding dethrones its claim to be the first bird.

"Professor Xu and his colleagues show that the evolutionary pattern varies according to their different analyses.

"Some show Archaeopteryx as the basal bird; others show it hopped sideways into the Deinonychosaurs.

"New fossils like Xiaotingia can make it harder to be 100% sure of the exact pattern of relationships."

According to Prof Witmer, little is certain in trying to determine the earliest bird and new findings can rapidly change perspectives.

"The reality is, that next fossil find could kick Archaeopteryx right back into birds. That's the thing that's really exciting about all of this."

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Saturday, 23 July 2011

US targets Iceland on whalemeat exports

US targets Iceland on whalemeat exports

A whale carcass is dragged into the processing plant at Havlur Fin whale carcasses are landed and flensed at the Hvalfjordur plant

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The US has opened the door to trade sanctions on Iceland over its hunting of fin whales and exports of whalemeat.

Commerce Secretary Gary Locke has formally told President Obama that Iceland's hunt threatens the species, which is globally endangered.

The president has 60 days to give his response, which can include trade bans.

Iceland resumed commercial whaling in 2006, and the fin whale catch has since risen to about 150 per year, with most of the meat exported to Japan.

But Iceland's fisheries minister said the country's whaling was based on "sound science".

"Iceland's disregard for the International Whaling Commission's (IWC) global moratorium on commercial whaling is unacceptable," said Mr Locke.

"Its harvest of whales and export of fin whale meat threaten an endangered species and undermine worldwide efforts to protect whales.

"It's critical that the government of Iceland take immediate action to comply with the moratorium."

He also notes the country's smaller annual catch of minke whales. Most of this meat is eaten locally, though some has been exported.

Stock take

Iceland left the IWC in 1992, but controversially re-joined a decade later with the condition that it could resume commercial whaling in 2006, which it did.

The Legalities of Whaling

  • Objection - A country formally objects to the International Whaling Commission (IWC) moratorium, declaring itself exempt. Example: Norway
  • Scientific - A nation issues unilateral "scientific permits"; any IWC member can do this. Example: Japan
  • Indigenous (aka Aboriginal subsistence) - IWC grants permits to indigenous groups for subsistence food. Example: Alaskan Inupiat

Generally, commercial whaling has been banned since 1986.

Iceland's Fisheries Minister Jon Bjarnason said he was surprised at the US move given that Icelandic whaling was "based on sound science" and sustainable.

"The annual quota of minke whales is 216 from a stock of approximately 70,000 animals, and the annual quota of fin whales is 154 from a stock of approximately 20,000 animals," said a ministry statement.

"The fin whale stock in the North Atlantic is abundant and in very good shape, and is in no way connected to the stock in the Southern Ocean which is in a poor state."

The fin whale quota is calculated by Icelandic scientists based on computer models developed under the IWC's aegis.

The models can be "tuned" to produce quotas that are more or less cautious.

The current Icelandic quota is about three times higher than the figure the IWC would recommend based on the more conservative tuning it has decided is appropriate.

Sanctions call

The process Mr Locke has instigated is "certification" under the Pelly Amendment to the Fishermen's Protective Act of 1967.

Guide to whales (BBC)

He recommends measures stopping short of a trade sanction, including instructing diplomats to raise the issue in talks with their Icelandic counterparts, and reviewing any projects in which the US co-operates with the Arctic nation.

One possible casualty could be a proposed pan-Arctic search and rescue station near Reykjavik, for which Iceland is seeking US support.

But his letter to Mr Obama notes that "the Pelly Amendment authorises you to direct the Secretary of the Treasury to prohibit the importation into the United States of any products from Iceland..."

A number of anti-whaling groups have been calling on the US to take such a step; and the Whale and Dolphin Conservation Society (WDCS) described Mr Locke's action as "a massive step forward".

"The only way to make sure that whaling is finally ended in Iceland is for the president to send a strong and unambiguous message to Iceland's whaling industry - and that means sanctions," said Kate O'Connell.

The US has certified Iceland on several previous occasions over whaling, but has yet to impose trade restrictions.

However, there is a feeling among US officials that the size of the whalemeat trade to Japan, plus smaller exports to other countries, presents a new and serious threat to the well-being of Atlantic fin whales.

The company behind the fin whale trade, Hvalur hf, has not hunted any this year because of poor market conditions in Japan following the March earthquake and tsunami.

But it does intend to take to the seas again if and when the market improves.

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Monday, 11 July 2011

Orangutan genome 'evolved slowly'

Orangutan genome 'evolved slowly'

Orangutan Evolution of the orangutan genome has proceeded more slowly than in other great apes

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Scientists have released a draft sequence of the orangutan genome, revealing intriguing clues to the evolution of great apes and humans.

The work suggests orangutans may be genetically closer to the proposed ancestral great ape than are chimps, gorillas and humans.

Details of the research are outlined in the journal Nature.

Two modern species of orang-utan live on the islands of Borneo and Sumatra respectively; both are under threat.

Of the great apes, the orangutan is the most genetically distant from humans.

Fossil finds show that it once had a wider range across South-East Asia; modern populations are threatened by the destruction of their forest habitat and other human activities such as trapping and selling the juvenile apes as pets.

An international team led by Devin Locke, from the Washington University School of Medicine in St Louis, US, sequenced the full genome of a female Sumatran orangutan named Susie.

With Susie's data as a reference, the researchers took advantage of next-generation sequencing technology to obtain lower resolution data on the genomes of 10 additional orangutans - five from Sumatra and five from Borneo.

The team's analysis reveals that the orangutan genome has experienced a slower rate of evolution than those of other great apes, with fewer rearrangements, duplications and repeats in the sequence.

This suggests their genomes are closer to that of the putative ancestral great ape, researchers say.

The researchers also compared 14,000 human genes with their equivalents in the orangutan, chimpanzee, macaque and dog.

The results suggest that genes involved in visual perception and the metabolism of molecules known as glycolipids have been particularly exposed to natural selection in primates.

Species split

"Changes in lipid metabolism may have played a big part in neurological evolution in primates, as well as being involved in the diversity of diets and life history strategies," said co-author Dr Carolin Kosiol, from the University of Veterinary Medicine, Vienna.

"Apes, especially orangutans, have slower rates of reproduction and much lower energy usage than other mammals. It would be very valuable to sequence more primate genomes to enable more comparative analysis of this kind and thus help us understand the evolution of primates and our own species."

The results also provide an estimate of when the Sumatran species split from the Bornean species: 400,000 years ago. This is more recent than other studies have suggested.

The data show that the Sumatran orangutan is more genetically diverse than the Bornean species, despite the fact that the Sumatran apes are now fewer in number than their Bornean cousins.

Genetic diversity could be important for conservation efforts, because it can be related to the ability of those populations to stay healthy and adapt to changes in their environment.

There are thought to be some 40,000-50,000 Bornean orangutans left in the wild; the Sumatran orangutan is believed to number only 7,000-7,500 individuals.

Paul.Rincon-INTERNET@bbc.co.uk

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Monday, 3 January 2011

Now, we have discovered the Denisovans

All change: Theories of human ancestry get an overhaul

View from a rock above Denisova cave on to the excavation field camp (Johannes Krause) The Denisovans are known from one location in Siberia, but they probably ranged more widely

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For over 150 years the name "Neanderthal" has been household property.

And it has become associated with dim-witted, ape-like brutes that scurried across vast ice-covered wastes waiting for the day when our ancestors - the intelligent and modern humans - would wipe them from the face of the Earth.

Now, we have discovered the Denisovans and I wonder what image we will choose to give them.

But there are already hints that suggest that the status quo will prevail and we will find reasons for making these people a little bit less clever than our direct ancestors.

The irony is that the scientific community is going to have to come round to the acceptance that the Denisovans and the Neanderthals also belonged to the species which we call Homo sapiens.

The Denisovans, for that is how we must know them (for now as the authors of a recent paper in Nature have preferred not to give them a scientific name), lived in southern Siberia.

We do not know how much further their range extended but it seems highly unlikely that they were confined to this region alone.

The site in which their remains were found seems to have been occupied over two periods, one older than 50,000 years ago and the other between 30,000 and 23,000 years ago.

It seems that it is not possible at this stage to determine whether the Denisovans occupied the site in one or other period, or both. Either way they must have lived close to Neanderthals or our own ancestors, depending on which time period they lived in.

An earlier study already showed that Neanderthals contributed a percentage of their genome to some of us, right across Eurasia from the west to the extreme south-east.

The present study shows that the Denisovans were closer genetically to the Neanderthals than to us but that we all shared a remote common ancestor.

Reality check

The Denisovans do not seem to have contributed much to the European gene pool but their genes made it all the way into that of the Melanesians.

Put together, this evidence shows us that humans formed an interwoven network of populations with varying degrees of gene flow between them. Some humans may have looked quite different from each other, revealing a combination of adaptation to local environments and genetic drift, but it does seem as though those differences were not large enough to prevent genetic interchange.

Denisovan tooth

DNA from ancient remains shows the Denisovans shared a common ancestor with Neanderthals

I have suggested that humans, at any point in time in our evolutionary history, behaved as a polytypic species; they consisted of an array of regional populations clustered into geographical races which had not achieved independent species status - they could exchange genes when they met.

And this is not a new idea either. The great evolutionary biologist Ernst Mayr proposed it for the human species as far back as 1950! An obsession with turning each new fossil into a distinct species has clouded the biological reality that we are now retrieving.

One aspect of the findings of this recent study shows that the Neanderthals experienced a severe genetic bottleneck in the course of their history which means that their overall genetic diversity was much lower than that of present-day humans.

The Denisovans seem to have escaped the bottleneck too. Now, the interesting point for me is that the bottleneck, affecting all Neanderthals, was an ancient one.

It predated the arrival of modern humans into Eurasia and thus must have been the result of an ecological impact and not competition.

This conclusion is exactly what I have been predicting over the past decade, that Neanderthal populations were in decline for a long time and well before the arrival of modern humans.

Food for thought

Almost concurrently with the Denisova findings, a paper published in the US Proceedings of the National Academy of Sciences (PNAS) journal looked at an unusual case - a family group of Neanderthals who lived in northern Spain and whose remains were preserved.

These Neanderthals from El Sidrón have provided DNA that reveals that the males were very similar to each other but the females were not. The conclusion is that Neanderthals were patrilocal - the males stayed put while the females wandered between clans and tribes.

Archaeologists excavate the cave in El Sidron in Asturias, Northern Spain Researchers have retrieved DNA from a Neanderthal family found at El Sidron cave (pictured)

What is more, these Neanderthals lived in small groups with low genetic diversity. Added to the Denisova paper findings, we can begin to understand the population biology of the Neanderthals. As I have suggested previously, their populations became heavily fragmented and gene flow between them became reduced.

They were in crisis but not because of the arrival of modern humans. Like pandas today they were in danger of extinction.

They were not in such danger because they were ape-like brutes either. A paper published this week in the Proceedings of the National Academy of Sciences has provided conclusive evidence that Neanderthals regularly ate plants and even cooked them before eating them!

A detailed study of Neanderthal teeth from Spy in Belgium and Shanidar in Iraq found traces of plant matter including grass seed starches that had been cooked. We had suspected that Neanderthals consumed plants for some time, and it was logical to do so, but now we have the evidence.

So those who claimed that Neanderthals only ate meat, an almost physiological impossibility, have to rethink their argument.

Seafood platter

In 2008, we published evidence of marine mammal and mollusc consumption by Neanderthals in Gorham's Cave, also in the PNAS journal. I have been arguing that omnivory is a defining characteristic of the genus Homo, including the Neanderthals, and these latest findings have confirmed this conclusion.

So the Neanderthals weren't stupid apes but humans, and they interbred with our own ancestors. Yet they were affected by environmental perturbation and went extinct.

Gibraltar (BBC) Neanderthals living at Gibraltar enjoyed a broad menu including monk seals

This is a lesson for us all to learn. But in spite of the evidence there are those who will resist. A hallmark, for the archaeologists, of modern humanity has been the Upper Palaeolithic technology.

In recent years the boundary between this technology and its makers has become increasingly diffuse and I would argue that technology can no longer be used as proxy for human taxa.

Now, the findings at Denisova have included typically Upper Palaeolithic technology. It would be ironic if we were to establish that it was the Denisovans, not modern humans, who had made them.

But the authors of the Denisova paper are unsure of the association between the bones and the tools and have opted for "the reasonable hypothesis that the phalanx and molar belong to the older occupation".

In other words the Denisovans lived prior to 50,000 years ago and the tools were made between 30,000 and 23,000 years ago by invisible humans.

Professor Clive Finlayson is director of the Gibraltar Museum and adjunct professor in the Department of Social Sciences at the University of Toronto. He is the author of Neanderthals and Modern Humans (Cambridge University Press, 2004) and The Humans who went Extinct (Oxford University Press, 2009).

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Thursday, 23 September 2010

Cerebral malaria may have passed

Cerebral malaria may have passed from gorillas to us

Gorilla (Nature) Gorillas may be the source of human cerebral malaria

Humans may have originally caught malaria from gorillas, scientists say.

Until now, it was thought that the human malaria parasite split off from a chimpanzee parasite when humans and chimpanzees last had a common ancestor.

But researchers from the US, three African countries, and Europe have examined malaria parasites in great ape faeces.

They found the DNA from western gorilla parasites was the most similar to human parasites.

Cerebral malaria

Malaria is caused by a parasite called Plasmodium, and is carried by mosquitoes.

The most common species found in Africa, Plasmodium falciparum, causes dangerous cerebral malaria. Over 800,000 people die from malaria each year in the continent.

Until now, scientists had assumed that when the evolutionary tree of humans split off from that of chimpanzees - around five to seven million years ago - so had Plasmodium falciparum.

This would have meant that humans and malaria co-evolved to live together. But new evidence suggests human malaria is much newer.

Dr Beatrice Hahn of the University of Birmingham, Alabama, in the US, is part of a team that had been studying HIV and related infections in humans and great apes.

Cerebral malaria (SPL) Cerebral malaria kills nearly a million people in Africa every year
DNA analysis

To study the DNA of infections in wild apes, you cannot use blood samples. So the team collected 2,700 samples of faecal material from two species of gorilla - western and eastern - and from common chimpanzees and bonobos, also known as pygmy chimpanzees.

They tried sequencing Plasmodium DNA from the faeces with techniques that use a large sample, and drew a genetic family tree to see which parasites were related. Dr Hahn said "When we did conventional sequencing, the tree didn't make any sense, because each sample contained a mixture of parasites."

They diluted the DNA so that they had just one parasite's genome represented in a single sample, and then amplified the DNA from there. This means they were able to separate the DNA from different species of the parasite much more effectively.

They then found the tree made much more sense. But they also found some surprising results.

The human Plasmodium was not very closely related to chimpanzee Plasmodium, as had been thought - but it was very closely related to one out of three species of gorilla Plasmodium from western gorillas in Central and West Africa.

There was more genetic variety in the gorilla parasites than in human parasites, and Dr Hahn said this means the gorilla is likely to be the "reservoir" - the origin of the human parasite.

"Other studies have just looked at chimps, so didn't find the gorilla parasite," said Dr Hahn. She added that some studies have looked at animals in captivity - so it is possible any parasites have "jumped" from their human keepers.

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Other studies have just looked at chimps, so didn't find the gorilla parasite”

End Quote Dr Beatrice Hahn University of Birmingham, Alabama, US
Cross-infection

The researchers, who report their findings in Nature, are now going to investigate further to see exactly how different the gorilla and human parasites are. Dr Hahn says that it is possible they are even the same species, and that cross-infection between humans and gorillas may be going on now.

Members of the team Dr Martine Peeters and Dr Eric Delaporte of the University of Montpelier in France are working with hunters and loggers in Cameroon, who spend a lot of time in the forests.

They will investigate whether these workers carry malaria parasites from the gorillas, which would suggest that new infections from other species can still happen.

They also do not yet know how badly apes are affected by malaria. Dr Hahn said that the team would now like to find out whether apes are able to catch the malaria parasite, without getting ill or dying in the way that humans do.

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Wednesday, 21 July 2010

The beautifully-preserved remains


Cave yields marsupial fossil haul
Nimbadon may have travelled in herds, say the scientists
Fossil hunters in Australia have discovered a cave filled with the 15-million-year-old remains of prehistoric marsupials.

The rare haul of fossils includes 26 skulls from an extinct, sheep-sized marsupial with giant claws.

The finds come from the Riversleigh World Heritage fossil field in north-west Queensland.

Continue reading the main story

Start Quote
To find a complete specimen like that and so many from an age range is quite unique”
End Quote
Liz Reed

Flinders University
The beautifully-preserved remains have been described in the Journal of Vertebrate Paleontology.

"It's extraordinarily exciting for us," said University of New South Wales palaeontologist Mike Archer, co-author of the research.

"It's given us a window into the past of Australia that we simply didn't even have a pigeonhole into before.

"It's an extra insight into some of the strangest animals you could possibly imagine."

The giant-clawed, wombat-sized marsupial is named Nimbadon lavarackorum; researchers discovered the first of the Nimbadon skulls in 1993.

The palaeontologists have been stunned at how well preserved the fossils were - and by how many were found.

Discovering such a large assemblage suggests the animals may have travelled in herds - like modern-day kangaroos, said palaeontologist Karen Black, who led the research team.


The specimens offer an extra insight into the life of an extinct creature But how the animals all ended up in the cave remains a mystery. One theory is that they accidentally plunged into it through an opening obscured by vegetation and either died from the fall, or became trapped and later perished.

The Nimbadon skulls include those of babies still in their mothers' pouches, allowing the researchers to study how the animals developed.

The skulls reveal that bones at the front of the face developed quite quickly, which would have allowed the baby to suckle from its mother at an extremely young age.

Those findings suggest that Nimbadon newborns developed very similarly to modern kangaroos - likely being born after a month's gestation and crawling into their mother's pouch for the rest of their development, Black said.

Nimbadon also may have something in common with another marsupial. The fossils revealed the creatures had large claws, which may have been used to climb trees - as koalas do, Dr Black explained.

"To find a complete specimen like that and so many from an age range is quite unique," said Dr Liz Reed of Flinders University in South Australia, who was not affiliated with the study.

"It allows us to say something about behaviour and growth and a whole bunch of things that we wouldn't normally be able to do."

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