sábado, 31 de janeiro de 2015

 Paleontology • 2015 

The Oldest Known Snakes from the Middle Jurassic-Lower Cretaceous provide insights on Snake Evolution

Ancient snakes: (top left) Portugalophis lignites (Upper Jurassic) in a gingko tree, from coal swamp deposits at Guimarota, Portugal;  (top right) Diablophis gilmorei (Upper Jurassic), hiding in a ceratosaur skull, from the Morrison Formation in Fruita, Colorado; (bottom) Parviraptor estesi (Upper Jurassic/Lower Cretaceous) swimming in freshwater lake with snails and algae, from the Purbeck Limestone in Swanage, England.
Illustrations: Julius Csotonyi |  DOI: 10.1038/ncomms6996
The previous oldest known fossil snakes date from ~100 million year old sediments (Upper Cretaceous) and are both morphologically and phylogenetically diverse, indicating that snakes underwent a much earlier origin and adaptive radiation. We report here on snake fossils that extend the record backwards in time by an additional ~70 million years (Middle Jurassic-Lower Cretaceous). These ancient snakes share features with fossil and modern snakes (for example, recurved teeth with labial and lingual carinae, long toothed suborbital ramus of maxillae) and with lizards (for example, pronounced subdental shelf/gutter). The paleobiogeography of these early snakes is diverse and complex, suggesting that snakes had undergone habitat differentiation and geographic radiation by the mid-Jurassic. Phylogenetic analysis of squamates recovers these early snakes in a basal polytomy with other fossil and modern snakes, where Najash rionegrina is sister to this clade. Ingroup analysis finds them in a basal position to all other snakes including Najash.

 Michael W. Caldwell, Randall L. Nydam,  Alessandro Palci and Sebastián Apesteguía. 2015. The Oldest Known Snakes from the Middle Jurassic-Lower Cretaceous provide insights on Snake Evolution. Nature Communications. 6. DOI: 10.1038/ncomms6996.

The oldest known snakes from the Middle Jurassic-Lower Cretaceous provide insights on snake evolution

Published -


The previous oldest known fossil snakes date from ~100 million year old sediments (Upper Cretaceous) and are both morphologically and phylogenetically diverse, indicating that snakes underwent a much earlier origin and adaptive radiation. We report here on snake fossils that extend the record backwards in time by an additional ~70 million years (Middle Jurassic-Lower Cretaceous). These ancient snakes share features with fossil and modern snakes (for example, recurved teeth with labial and lingual carinae, long toothed suborbital ramus of maxillae) and with lizards (for example, pronounced subdental shelf/gutter). The paleobiogeography of these early snakes is diverse and complex, suggesting that snakes had undergone habitat differentiation and geographic radiation by the mid-Jurassic. Phylogenetic analysis of squamates recovers these early snakes in a basal polytomy with other fossil and modern snakes, where Najash rionegrina is sister to this clade. Ingroup analysis finds them in a basal position to all other snakes including Najash.

quarta-feira, 28 de janeiro de 2015

First horses arose 4 million years ago

The oldest full genome sequence, recovered from ancient horse bone, pushes back equine origins by 2 million years.

Claudia Feh, Association pour le cheval de Przewalski

The Przewalski’s horse, recently brought back from the brink of extinction in Mongolia, is truly the last remaining wild horse, suggests the new study.
The humble horse has provided the oldest full genome sequence of any species — from a specimen more than half a million years old, found frozen in the permafrost of the Canadian Arctic. The finding, published in Nature today1, pushes back the known origins of the equine lineage by about 2 million years, and yields a variety of evolutionary insights.
The sequence was extracted from a foot bone of a horse that lived between 780,000 and 560,000 years ago. By sequencing the animal's genome, along with those of a 43,000-year-old horse, five modern domestic horse breeds, a wild Przewalski’s horse and a donkey, researchers were able to trace the evolutionary history of the horse family in unprecedented detail. They estimate that the ancient ancestor of the modern Equus genus, which includes horses, donkeys and zebras, branched off from other animal lineages about 4 million years ago — twice as long ago as scientists had previously thought.

“We have beaten the time barrier,” says evolutionary biologist Ludovic Orlando of the University of Copenhagen, who led the work with colleague Eske Willerslev. Noting that the oldest DNA sequenced before this came from a polar bear between 110,000 and 130,000 years old2, Orlando says: “All of a sudden, you have access to many more extinct species than you could have ever dreamed of sequencing before.”
The team was able to sequence such old DNA partly because of the freezing ground temperatures in the area where the bone was found, which would have slowed the rate of DNA decay.
But the researchers were also successful because they had perfected techniques for extracting and preparing the DNA to preserve its quality for sequencing. They targeted tissue within the fossil which has high DNA content, such as collagen. They also combined DNA sequencing techniques to get maximum DNA coverage — using routine next-generation sequencing with single-molecule sequencing in which a machine directly reads the DNA without the need to amplify it up which can lose some DNA sequences.
Now, a major challenge for the field is to apply these techniques to other species such as ancient human species, including Homo heidelbergensis and Homo erectus, which lived hundreds of thousands to more than 1 million years ago. But such specimens are unlikely to be found buried in the DNA-preserving permafrost.
”The real challenge right now in the field is combining these next-generation sequencing technologies with the possibility of analysing non-permafrost samples,” says Carles Lalueza-Fox, a palaeogeneticist at the Institute of Evolutionary Biology in Barcelona, Spain.

Wild horses

Orlando and Willerslev's paper hints at the other types of discovery that these technologies can enable. Their team, for instance, was able to support the contention that the Przewalski’s horse (Equus ferus przewalskii), which was brought back from near-extinction in Mongolia by captive-breeding programmes, is truly the last remaining wild horse when compared genetically with domesticated horses.
The researchers were also able to trace the size of the horse population over time by looking for genomic signatures of population size, and were thus able to show that populations grew in periods of abundant grassland, in between times of extreme cold.
But that is not surprising. Other researchers say that it is a proof of principle for how similar studies can be used to explore the factors that have driven evolution and speciation. “This kind of study is giving us novel views that show us the nuts and bolts of how evolution is working,” says Alan Cooper, director of the University of Adelaide's Australian Center for Ancient DNA.

Although Willerslev and Orlando say that it would theoretically be possible to resurrect the ancient horse by implanting a modern horse egg with the ancient DNA, they have no plans to do so. They say that it has been a formidable task just to assemble the genome from many small fragments of DNA. For now, they prefer to focus on further improving their techniques, before testing them on other samples.
When they have mastered the technique, Willerslev predicts that it will have a huge impact on evolutionary biology. “Ancient genomics will change a lot of the ways we look at evolution to date,” he says.
Follow Erika on Twitter at @Erika_Check.


  1. Orlando, L. et al. Nature http://dx.doi.org/10.1038/nature12323 (2013).
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  2. Miller, W. et al. Proc. Natl Acad. Sci. USA 109, E2382E2390 (2012).
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Rise of the coyote: The new top dog

Shape-shifting coyotes have evolved to take advantage of a landscape transformed by people. Scientists are now discovering just how wily the creatures are.

Wolf genes make the coyotes of northeastern North America bigger and stronger than those elsewhere.
Near the dawn of time, the story goes, Coyote saved the creatures of Earth. According to the mythology of Idaho's Nez Perce people, the monster Kamiah had stalked into the region and was gobbling up the animals one by one.

The crafty Coyote evaded Kamiah but didn't want to lose his friends, so he let himself be swallowed. From inside the beast, Coyote severed Kamiah's heart and freed his fellow animals. Then he chopped up Kamiah and threw the pieces to the winds, where they gave birth to the peoples of the planet.
European colonists took a very different view of the coyote (Canis latrans) and other predators native to North America. The settlers hunted wolves to extinction across most of the southerly 48 states. They devastated cougar and bobcat populations and attacked coyotes. But unlike the other predators, coyotes have thrived in the past 150 years. Once restricted to the western plains, they now occupy most of the continent and have invaded farms and cities, where they have expanded their diet to include squirrels, household pets and discarded fast food.
Researchers have long known the coyote as a master of adaptation, but studies over the past few years are now revealing how these unimposing relatives of wolves and dogs have managed to succeed where many other creatures have suffered. Coyotes have flourished in part by exploiting the changes that people have made to the environment, and their opportunism goes back thousands of years. In the past two centuries, coyotes have taken over part of the wolf's former ecological niche by preying on deer and even on an endangered group of caribou. Genetic studies reveal that the coyotes of northeastern America — which are bigger than their cousins elsewhere — carry wolf genes that their ancestors picked up through interbreeding. This lupine inheritance has given northeastern coyotes the ability to bring down adult deer — a feat seldom attempted by the smaller coyotes of the west.

The lessons learned from coyotes can help researchers to understand how other mid-sized predators respond when larger carnivores are wiped out. In sub-Saharan Africa, for example, intense hunting of lions and leopards has led to a population explosion of olive baboons, which are now preying on smaller primates and antelope, causing a steep decline in their numbers.

Yet even among such opportunists, coyotes stand out as the champions of change. “We need to stop looking at these animals as static entities,” says mammalogist Roland Kays of the North Carolina Museum of Natural Sciences in Raleigh. “They're evolving”.

At a fast rate, too. Two centuries ago, coyotes led a very different life, hunting rabbits, mice and insects in the grasslands of the Great Plains. Weighing only 10 to 12 kilograms on average, they could not compete in the forests with the much larger grey wolves (Canis lupus), which are quick to dispatch coyotes that try to scavenge their kills.

The big break for coyotes came when settlers pushed west, wiping out the resident wolves. Coyotes could thrive because they breed more quickly than wolves and have a more varied diet. Since then, their menu has grown and so has their range; they have invaded all the mainland United States (with the exception of northern Alaska) and Mexico, as well as large parts of southern Canada (see 'On the move').
The animals that arrived in the northeastern United States and Canada in the 1940s and 50s were significantly larger on average than those on the Great Plains, sometimes topping 16 kilograms. Kays and his colleagues studied the rapid changes in coyote physique by analysing mitochondrial DNA and skull measurements of more than 100 individuals collected in New York state and throughout New England. They found1 that these northeastern coyotes carried genes from Great Lakes wolves, showing that the two species had interbred as the coyotes passed through that region. “Coyotes mated with wolves in the 1800s, when wolf populations were at low density because of human persecution,” says Kays. In those circumstances, wolves had a hard time finding wolf mates, so they settled for coyotes.

Compared with the ancestral coyotes from the plains, the northeastern coyote–wolf hybrids have larger skulls, with more substantial anchoring points for their jaw muscles. Thanks in part to those changes, these beefy coyotes can take down larger prey; they even killed a 19-year-old female hiker in Nova Scotia in 2009. The northeastern coyotes have expanded their range five times faster than coyote populations in the southeastern United States, the members of which encountered no wolves as they journeyed east.

New to the city

Coyotes have even moved into Washington DC, appearing in Rock Creek Park in 2004, just a few miles from the White House. Christine Bozarth, a conservation geneticist at the Smithsonian Institution in Washington, has tracked their arrival and has shown that some of them are descended from the larger northeastern strain and carry wolf DNA2. Bozarth says the coyotes are there to stay. “They can adapt to any urban landscape; they'll raise their pups in drainage ditches and old pipes,” she says. She hopes that the coyotes will help to control the deer, whose numbers are booming. But Kays says that coyotes have not made a significant dent in the northeast's deer population. “Coyotes fill part of the empty niche, but they don't completely replace wolves,” he says.

Oddly enough, it is the smaller coyotes in the southeastern United States that seem to be having a real impact on deer. About the same size as western coyotes, the southeastern ones have begun to exploit a niche left empty by the red wolves (Canis lupus rufus) that once roamed the southeast and specialized in hunting the region's deer, which are smaller than those in the northeast.

John Kilgo, a wildlife biologist with the US Forest Service in New Ellenton, South Carolina, and his colleagues found in a 2010 study3 that South Carolina's deer population started to decline when coyotes arrived in the late 1980s. More recently, he and his colleagues have studied deaths among fawns, using forensic techniques right out of a murder investigation4. They analysed bite wounds on the carcasses and sequenced DNA in saliva left on the wounds. They also searched for scat and tracks left by the killers and noted how they had stashed uneaten remains. More than one-third of the fawn deaths were clearly caused by coyotes, and circumstantial evidence suggests that the true number might be closer to 80%. “Coyotes are acting as top predators on deer, and controlling their numbers,” says Kilgo.
At first, many researchers had a hard time accepting that conclusion because they thought that coyotes were too small to affect deer populations, Kilgo says. He hopes to study how the newly arrived coyotes will affect other members of the southeastern ecosystem, including wild turkeys and predators such as raccoons, foxes and opossums.
There is no danger that the southeastern coyotes will drive the abundant deer in that region to extinction. But at the northern extreme of their range, coyotes are threatening a highly endangered band of woodland caribou (Rangifer tarandus caribou) in the mature forests of Quebec's Gaspésie National Park. Logging and other changes there had taken a toll on the caribou even before coyotes arrived in the region in 1973 and settled into newly cleared parts of the forest. But then coyotes started hunting caribou calves and the population dropped even further.
A 2010 study5 found that coyotes accounted for 60% of the predation on these caribou, which now number only 140. Dominic Boisjoly, a wildlife biologist with Quebec's Ministry of Sustainable Development, Environment and Parks in Quebec City, says that the best way to protect the caribou would be to cease clear-cutting of the forest, thereby denying the predators a home.
Coyotes have been taking advantage of the changes wrought by humans for many thousands of years, according to a study of coyote fossils published this year6. Evolutionary biologist Julie Meachen at the National Evolutionary Synthesis Center in Durham, North Carolina, and Joshua Samuels at the John Day Fossil Beds National Monument in Kimberly, Oregon, made that discovery by measuring the size of coyote fossils dating back over the past 25,000 years. During the last ice age, coyotes were significantly larger than most of their modern counterparts and resembled the biggest of the present-day coyote–wolf hybrids in the northeast. They probably scavenged meat from kills made by dire wolves and sabre-toothed cats, and preyed on the young of the large herbivores, such as giant ground sloths, wild camels and horses, that thronged North America at that time.
But at the close of the ice age, about 13,000 years ago, most of the megafauna vanished — an extinction attributed to both climate change and the appearance of efficient Stone Age hunters. With them went the largest predators, allowing the smaller grey wolves to fill the vacant niche, which put them in competition with the largest coyotes. That conflict, as well as the loss of large herbivores, caused coyotes to shrink in stature. Within 1,000 years of the Pleistocene extinctions, coyotes had reached the same size as in most present-day populations.
Now, they're going through a whole new set of changes as they adapt to the modern landscape of North America. Genetic studies7 show that some coyotes are even interbreeding with dogs, which could lead to a different sort of hybrid animal. Researchers are struggling to keep up with the animals and their impacts as they lope into more new regions.
“Invading a landscape emptied of wolves may trigger a whole new pathway in terms of the coyote's evolution,” says Bill Ripple, an ecologist at Oregon State University in Corvallis. “And the coyote's arrival will have unpredictable effects on other species in the ecosystem.”

Dog's dinner was key to domestication

Genome study pinpoints changes that turned wolves into humanity's best friend.

Justin Paget/Corbis
No need to push back on your favorite pet's appetite for carbs: dogs appear to have evolved to digest starches.

Dogs now have an excuse for waiting under the dinner table: domestication may have adapted them to thrive on the starch-filled foods that their owners eat.

A study published in Nature1 today finds that dogs possess genes for digesting starches, setting them apart from their carnivore cousins — wolves.
The authors say the results support the contentious idea that dogs became domesticated by lingering around human settlements. “While it’s possible that humans might have gone out to take wolf pups and domesticated them, it may have been more attractive for dogs to start eating from the scrap heaps as modern agriculture started,” says Kerstin Lindblad-Toh, a geneticist at Uppsala University in Sweden, who led the work.

Canine-domestication researchers agree that all dogs, from beagles to border collies, are the smaller, more sociable and less aggressive descendants of wolves. But neither the time nor the location of the first domestication is known: fossils place the earliest dogs anywhere from 33,000 years ago in Siberia to 11,000 years ago in Israel, whereas DNA studies of modern dogs put domestication at least 10,000 years ago, and in either Southeast Asia or the Middle East. Many researchers believe that dogs were domesticated more than once, and that even after domestication, they occasionally interbred with wild wolves.

Growing together

Lindblad-Toh and her team catalogued the genetic changes involved in domestication by looking for differences between the genomes of 12 wolves and 60 dogs from 14 different breeds. Their search identified 36 regions of the genome that set dogs apart from wolves — but are not responsible for variation between dog breeds.

Nineteen of those regions contained genes with a role in brain development or function. These genes, says Lindblad-Toh, may explain why dogs are so much more friendly than wolves. Surprisingly, the team also found ten genes that help dogs to digest starches and break down fats. Lab work suggested that changes in three of those genes make dogs better than meat-eating wolves at splitting starches into sugars and then absorbing those sugars.

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Kerstin Lindblad-Toh thinks that the evolution of dogs has been shaped by their dinner. She spoke to Ewen Callaway.
Most humans have also evolved to more easily digest starches2. Lindblad-Toh suggests that the rise of farming, beginning around 10,000 years ago in the Middle East, led to the adaptations in both species. “This is a striking sign of parallel evolution,” she says. “It really shows how dogs and humans have evolved together to be able to eat starch.”

Dinner with friends

However, Greger Larson, an evolutionary archaeologist at Durham University, UK, very much doubts that genes involved in digesting starches catalysed domestication, pointing out that the earliest dog fossils predate the dawn of agriculture. His team plans to analyse DNA preserved in dog fossils, to discover when the genetic variations involved in domestication first emerged.

Robert Wayne, a geneticist at the University of California, Los Angeles, who is also studying ancient dog genomes, says that starch metabolism could have been an important adaptation for dogs. However, he thinks that such traits probably developed after behavioural changes that emerged when humans first took dogs in, back when most of our forebears still hunted large game.

Nevertheless, the study adds to evidence that dogs should not eat the same food as wolves, says Wayne, who points out that dog food is rich in carbohydrates and low in protein compared with plain meat. “Every day I get an email from a dog owner who asks, should they feed their dog like a wolf," says Wayne. "I think this paper answers that question: no.”

Human evolution: Small remains still pose big problems

Ten years after the publication of a remarkable find, Chris Stringer explains why the discovery of Homo floresiensis is still so challenging.

Jim Watson/AFP/Getty
The adult skull of Homo floresiensis (centre) at the 2004 press conference announcing the species' discovery.
In early 2004, the Australian palaeoanthropologist Peter Brown teasingly e-mailed me pictures of a strange-looking skull, asking what I thought it was. I knew that he had been working in east Asia, so I guessed that the images might represent the first discovery of a very primitive member of our genus, Homo, from somewhere like China.
Gradually, Brown revealed the even more astonishing news of the skull's remote location and recent age. That October, he, Mike Morwood and colleagues published analyses in this journal1, 2 with the controversial proposal that the tiny skull and its associated skeleton represented a new human species. They named it Homo floresiensis, which Morwood dubbed 'hobbit', owing to its diminutive stature — a moniker that the global press quickly ran with.
The researchers posited that a primitive hominin persisted into the era of anatomically modern humans2 and lived in Flores, part of the remote string of Wallacean islands east of Java that have remained isolated since their formation (see 'How did the hobbit get to Flores?'). Controversy about this species continues to this day, including whether it even belongs in Homo.

Unexpected trip

In 2004, like most palaeoanthropologists, I thought that only modern humans (Homo sapiens — like us) had travelled beyond southeast Asia in the past 60,000 years. By then, people had devised sea-going watercraft essential for such a journey. It seemed unlikely that more-ancient humans could have made such a voyage3.


Ewen Callaway chats to four experts about the discovery of Homo floresiensis and the big impact created by the little fossil.
The excavations that first led to the idea that ancient humans did so began in 2001. Morwood, a New Zealand-born archaeologist, led an international team in the huge Liang Bua (meaning 'cool cave') on Flores, hoping to find evidence of the earliest modern humans to colonize Wallacea, Australia and New Guinea. The project reopened trenches several metres deep from previous Dutch and Indonesian work. It soon yielded promising finds: stone tools that seemed to be more than 10,000 years old, and fossils of a pygmy form of the extinct elephant-like Stegodon.
In 2003, at a depth of around 6 metres, the team encountered a small skeleton (LB1) that they first thought must represent a modern human child. Then they noticed other details: the wisdom teeth in its jaws had fully erupted, and the tiny skull showed definite brow ridges above its large eye sockets.
The skeleton was dated from associated materials to less than 20,000 years old. Morwood and colleagues argued that it represented a unique example of insular dwarfism in humans. This is a well-known process whereby large mammals isolated on islands evolve smaller bodies in response to limited resources and the lack of predators4.
Morwood and colleagues argued that a population of Homo erectus could have travelled, perhaps by boat, to Flores from Java (500 kilometres away), where H. erectus was first identified in the 1890s. Java, having been repeatedly connected to the rest of Asia over the past 2 million years when sea levels were low, was thought to mark the farthest extent from Africa of colonization by ancient humans. Morwood and colleagues posited that Flores's ancient settlers underwent island dwarfing, in parallel with other colonizing mammals such as Stegodon. Stone tools associated with Stegodon bones in Liang Bua suggested that H. floresiensis could have hunted and butchered these animals.

Ongoing arguments

Stone tools discovered elsewhere on Flores, analyses of which were published5 in 2010, suggest that potential ancestors of H. floresiensis could have been on the island a million years ago. But considering an island on the other side of the world — Britain — with its discontinuous record of human settlement over 900,000 years, I can also imagine episodic human colonizations on Flores.
Nature special: The hobbit at 10
In 2009, a collection of studies6 analysed LB1 in more detail, along with other fossils attributed to H. floresiensis, including a second jawbone (LB6), and fragments of limb bones of up to eight more individuals. Features such as LB1's broad, flared hipbones, short collarbone, and forwardly positioned shoulder joint all resembled the pre-human group known as australopithecines ('southern apes'), which includes individuals such as the 3.2-million-year-old skeleton of 'Lucy', comparable in size to LB1.
These studies did not settle ongoing arguments about whether the finds represented a small, early human (a H. erectus shrunk through insular dwarfing) or an abnormal modern one, wrongly dated and analysed3, 4. There were further problems: in late 2004, Teuku Jacob, a now-deceased Indonesian palaeoanthropologist, appropriated the specimens to conduct his own work in Yogyakarta. By the time the fossils were returned to Jakarta, following international pressure, some had been damaged irreparably4.
The small brain of H. floresiensis has provoked particularly fierce controversy. Some, citing parallels in other dwarfed mammalian species7, 8, argue that it could derive from a H. erectus template, diminished but human in structural organization. Others rule out dwarfing, insisting that the braincase is much smaller than would be expected if a H. erectus body were scaled down. They argue that the shape of the brain reflects pathology — perhaps a condition called microcephaly9.
Various pathologies can explain some of the unusual aspects of the LB1 skeleton. But in my view, no syndrome so far proposed can account for the totality of evidence from Liang Bua. Neither cretinism, Laron syndrome nor Down's syndrome duplicate the full suite of features.
H. floresiensis: Handout/AAP Image; H. habilis: Carolina Biological Supply/Visuals Unlimited/SPL; Australopithecus: The Natural History Museum/Alamy; H. erectus: Tom McHugh/SPL

Classifying the hobbit

From the beginning, Brown and Morwood were torn over how to classify the fossil. In the first drafts of their paper they even created an entirely new genus for LB1 to reflect its unique combination of human and non-human traits — 'Sundanthropus floresianus'. But in the face of insistent reviewers, they shifted to the idea that their find was a dwarfed version of H. erectus4.
Both Morwood and Brown indicated later that they were not convinced by that model6, 10, and I join them in their doubts. The tiny brain of LB1, its body shape, and its foot, hand and wrist bones look more primitive than those of any human dating to within the past million years. Primitive traits of the wrist bones and jaw are replicated in at least one more individual from the site10, 11. Like LB1, the LB6 lower jaw is small, lacks a chin, and shows internal bony reinforcements most like those in pre-human fossils more than 2 million years old10.
Nature Collection: History of the hobbit $4.99
Ten years on, it is still very difficult to decide between competing views on where the hobbit came from (see 'Where does the hobbit belong?'). Island dwarfing from a local H. erectus population is probably still the most widely accepted idea, although this would require the re-emergence of primitive traits as well as convergence on H. sapiens in features such as tooth size and shape12.
A more primitive origin, from a more ancient H. erectus population (such as the 1.8-million-year-old fossils found at Dmanisi in Georgia) would require less extreme dwarfing, but would still need the re-emergence of primitive traits. An even more primitive template, closer to Homo habilis or the pre-human australopithecines, is a closer match for the reinforced jawbone, brain and body size, wrist morphology, and body shape, but would require still more convergences on later Homo morphology in features such as cranial thickness, retracted face and dental reduction.
Achmad Ibrahim/AP
Liang Bua cave on the Indonesian island of Flores, the discovery site of Homo floresiensis.
We need more bones from Liang Bua to establish the morphological variation of H. floresiensis and set pathological explanations to rest. At present we do not even know the extent of sexual dimorphism in the species — would a male skeleton be much larger and more H. erectus-like?
Isotope studies and analyses of preserved dental tartar could help to reconstruct the H. floresiensis diet, and investigations of dental microstructure might place the species taxonomically, because primitive hominins grew distinctly faster than H. erectus and later humans3. Even small amounts of ancient DNA would greatly clarify its evolutionary history, but it will require both technological breakthroughs and good fortune to acquire analysable samples from the warm, wet conditions of Liang Bua.
Significant work on re-evaluating the dates of the site, fossils and archaeology was under way before Morwood's untimely death in 2013. The results, due soon, will undoubtedly affect our views of H. floresiensis, and when and why it went extinct.

More surprises

I think that there are more surprises to come from the rest of Wallacea. If the ancestors of H. floresiensis reached Flores, perhaps they also dispersed to other islands, and the experiment in human evolution revealed in Liang Bua might have equally remarkable parallels elsewhere — for example on Sulawesi, the Philippines and Timor. As Morwood pointed out4, 6, the powerful currents around Indonesia would have favoured transport from Sulawesi (north of Flores) rather than from Java, where the nearest H. erectus fossils have been found. The possibility of accidental rafting on mats of vegetation in such a tectonically active region must also be considered; in the 2004 Indian Ocean tsunami, some people who survived on floating debris were dispersed more than 150 kilometres.
If the H. floresiensis lineage had a more primitive origin than the oldest known H. erectus fossils so far identified in Asia, then we would have to re-evaluate the dominant explanation for how humans arose and spread from Africa. Most current thinking assumes that the first dispersal from Africa was just before the time of the Dmanisi fossils3. An ancient origin for the hobbit would make that dispersal earlier and more complex13. It would mean that a whole branch of the human evolutionary tree in Asia had been missing until those fateful discoveries in Liang Bua.

Ape-like fossils show hints of human ancestry

The hominin Australopithecus sediba was a hodgepodge of simian and human-like features.

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Lee R. Berger/University of the Witwatersrand
A reconstruction of the Australopithecus sediba skeleton (centre), compared to those of a modern human (left) and a chimpanzee (Pan troglodytes; right).

The two-million-year-old remains of a novel hominin discovered in August 2008 are an odd blend of features seen both in early humans and in the australopithecines presumed to have preceded them. A battery of six studies1–6 published today in Science scrutinizes the fossils of Australopithecus sediba from head to heel and yields unprecedented insight into how the creature walked, chewed and moved. Together, the studies suggest that this hominin was close to the family tree of early humans — although it remains controversial whether it was one of our direct ancestors.

“We see evolution in action across this skeleton,” says Lee Berger, a palaeoanthropologist at the University of the Witwatersrand in Johannesburg, South Africa. For instance, whereas the creature’s arms are ape-like, its hands and wrists are remarkably like those of humans. And although the hominin’s pelvis is shaped like a modern human's, its torso included a narrow upper rib cage like those found in apes.

One of the six studies focused on Au. sediba’s teeth1, comparing 22 different aspects across hundreds of teeth from several other species of australopithecines and thousands of early human teeth. Tooth similarities among the species are more likely to signify common ancestry than independent evolution towards a beneficial design, says Debbie Guatelli-Steinberg, an anthropologist at Ohio State University in Columbus. That's because most of the characteristics the team chose to study, such as the subtle curvature of a portion of the tooth’s surface, are not likely to be evolutionarily useful.
Of the 22 dental traits considered by Guatelli-Steinberg and her colleagues, Au. sediba shared 15 with Australopithecus africanus and 15 with early humans. Moreover, says Guatelli-Steinberg, four of the traits shared by Au. sediba, Au. africanus and early humans are not seen in earlier hominins — another sign of the close evolutionary relationship between these two australopithecines and early humans, she notes.
One of the most telling analyses in the set of studies relates to Au. sediba’s legs, and how the creature might have walked2. For biomechanical models to adequately reconstruct a creature’s stride and gait, researchers need to provide anatomical data about five body parts: the heel, ankle, knee, hip and lower back, says Jeremy DeSilva, a functional morphologist at Boston University in Massachusetts. “With Au. sediba, we have all five, and the anatomy is flat-out different from what we see in other australopithecines,” he notes. The individual pieces seem strange in isolation, but together they tell a story, DeSilva adds.
Reconstruction: Peter Schmid/Photo: Lee R. Berger/University of the Witwatersrand
The reconstructed skull and mandible of Australopithecus sediba.

Shuffle and swagger

His team’s models show that Au. sediba would have walked very differently than modern humans. In each stride, the first part of the creature’s foot to contact the ground would have been the outer edge of the foot. (In modern humans, the heel strikes the ground first.) As weight increasingly shifted to that foot, the foot would have rolled inwards, causing a tremendous amount of rotation at each of the leg joints. The result, says DeSilva, is a shuffling, swaggering, flat-footed gait with short strides. “Whoa!” he says. “We didn’t expect that.”
Au. sediba’s mode of walking was probably a compromise, enabling it to shamble across grasslands from one patch of woodland to another and then clamber around within trees once it reached the forest, says DeSilva.

Physiological analyses of Au. sediba’s torso support this notion3. The narrow, ape-like upper body suggests that the creature wouldn’t have had large lung capacity, says anthropologist Peter Schmid, who led the torso work and recently retired from the University of Zurich in Switzerland. Also, the structure of the shoulder joints — an elevated, 'shrugged' arrangement well suited to climbing in trees and hanging from branches — hints that Au. sediba couldn’t have swung its arms well when it walked. Together, Schmid notes, these factors would have limited the creature’s ability to breathe heavily when walking or running.

Although most aspects of Au. sediba’s anatomy suggest that it is a close relative of early humans of the genus Homo, exactly where the species lies within human evolution isn’t yet clear. “We’re trying to be cautious with our interpretations,” says Berger.

Nevertheless, “from what we’re seeing, Au. sediba is a possible ancestor of Homo”, Berger says. “But if the creature is an ancestor of Homo, then the genus arose in a very different way than previously hypothesized.”
However, ancestry and close kinship are two different things, and some within the palaeoanthropology community dispute that the hominin was a direct human ancestor. One such researcher is Donald Johanson, a palaeoanthropologist at Arizona State University in Tempe who wasn’t involved in the new studies. In Ethiopia in 1974, Johanson and colleague Tom Gray discovered the fossils of “Lucy” (Au. afarensis)— a 3.2-million-year-old hominid whose 40-percent-complete skeleton is one of the most renowned fossils in the world.
“From what I have seen of the fossils, I think Au. sediba is another species of Australopithecus that confirms species diversity in early hominin evolution,” says Johanson. Although Au. sediba “abundantly demonstrates a unique set of anatomical features”, he notes, the species was probably a dead-end branch on the hominin family tree.


  1. Irish, J. D., Guatelli-Steinberg, D., Legge, S. S., de Ruiter, D. J. & Berger, L. R. Science 340, 1233062-1–1233062-4 (2013).
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  2. DeSilva, J. M. et al. Science 340, 1232999-1–1232999-5 (2013).
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  3. Schmid, P. et al. Science 340, 1234598-1–1234598-5 (2013).
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  4. Williams, S. A. et al. Science 340, 1232996-1–1232996-5 (2013).
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  5. De Ruiter, D. J. et al. Science 340, 1232997-1–1232997-4 (2013).
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  6. Churchill, S. E. et al. Science 340, 1233477-1–1233477-5 (2013).

Lucy discoverer on the ancestor people relate to

Donald Johanson reflects on the enduring charisma of the Australopithecus afarensis fossil he found 40 years ago.

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Donald Johanson with Lucy in a 1982 picture.
“Feeling really lucky,” Donald Johanson wrote in his diary the morning of 24 November 1974, while staying at a remote camp in northern Ethiopia’s Afar region. Hours later, the palaeoanthropologist, now at Arizona State University in Tempe, happened upon the 3.2-million-year-old remains of a small-bodied early human, possibly on the lineage that gave rise to Homo sapiens. He and his collaborators named it Australopithecus afarensis, and the skeleton became known to the world as Lucy. Forty years on, Johanson, now 71, talks about the discovery and Lucy’s enduring importance and appeal.

What did scientists know about early human evolution before Lucy?

Before my discoveries at the site of Hadar in Ethiopia, we had relatively few fossil species, and only a handful that were as old as 3 million years: There was a piece of arm, a single tooth, a chunk of jaw and maybe a bit of skull. But we didn't have any idea of what early hominids looked like.

What took you to Ethiopia in the early 1970s?

A young geologist by the name of Maurice Taieb [who is now director of research at the European Centre of Research and Teaching of Geosciences of the Environment in Aix-en-Provence, France] had been exploring the Afar region, and during the course of that preliminary work in the late 1960s, he encountered large areas that were very fossil-rich. He asked me to accompany him in 1972 to this region in the Afar, and we spent six weeks in the field. We were dazzled by the high concentrations of fossils, the deep sedimentary sequences, and the presence of volcanic ash, which would help determine a firm geochronological framework. In 1973 we decided to plant our flag at Hadar, which is where the Awash River turns east, and have been working on-and-off there ever since.

What was the expedition like?

It was very remote. There was no paved road to this area, so it was difficult to supply. On the plus side, there was a permanent source of water — the Awash River — nearby. Temperatures were regularly 110, 115 °F (43–46 °C) and you lived in a little tent for two and a half months. I was back to the site a couple years ago, and it's not as easy for me as it was when I was 28 years old. It was a place where you had to have the drive to work.

Tell me about the day of 24 November 1974.

It was a Sunday morning, and I was catching up on my field notes. I think I wrote: “I'm feeling really lucky that we're going to make a major discovery,” because we were in the process of training our eyes, training our collectors. One of our Ethiopian colleagues had found several jaws in the early days of that 1974 expedition, and I had a sense that it was going to be a very important field season.
Yet I didn't want to go to the field that day, but my graduate student encouraged me to go with him, because we had to do some mapping of fossils. So we went out to survey for a couple hours. Walking back to our car, I glanced over my shoulder and spotted this funny little elbow bone that we had missed in the morning, and it immediately said hominid to me. It didn't look like a monkey, it certainly wasn't any kind of small antelope, and when I examined it more closely, I could see it was from a human ancestor. It was very small. And then, to my great surprise and reward, I looked up the slope and there were fragments of the skeleton eroding on this little hillside.
We saw a bit of leg bone and a little bit of jaw. But it was over the next two weeks that most of the skeleton was recovered. We were disappointed that the cranium had eroded out earlier, and all we had was a pretty good chunk of the occipital bone, enough to give us at least a ballpark view that this was pretty small-brained. But she was marvellous as she began to be pieced together in camp over those two weeks. You could see her coming to life.

What was the mood in camp?

Everybody was just thrilled and galvanized by this discovery. What amazed me was how quickly she picked up her nickname. I had a Beatles tape playing the night we celebrated her discovery. It is true that “Lucy in the Sky with Diamonds” was playing. This woman just suggested calling her Lucy, but it was kind of a throwaway line. I didn't really concentrate on it. But by breakfast the next morning, everyone was saying “Are we going back to the Lucy site?”, “Do you think we'll find more of Lucy's skull?” and so on.

What made Lucy so important?

She told us a lot about bipedalism: that changes in the foot, the ankle, the knee and the hip happened well before Lucy, because the biomechanics of bipedalism in afarensis are virtually identical to our own. I think she was also very important because she drew attention to an entirely new segment in the Great Rift Valley, one that had been overlooked for so long because of its remoteness. She was a real catalyst for field workers.

How has your understanding of Lucy changed in the last 40 years?

I think that we realized that there are certain features in her skeleton that were left over from her arboreal ancestry. While we were closed to that idea in the 1970s, we realized that probably Lucy and her species did spend some time in the trees. With the discovery of Australopithecus afarensis at other sites — her species is known by over 400 specimens now — it showed they lived in a geographically widespread area. There were probably a variety of habitats, which reflects some level of adaptability in this species that contributed to its long-term survival.

Have you ever tried to imagine the life that Lucy led?

On my first visit to Gombe [Gombe Stream National Park in Tanzania, where Jane Goodall studied wild chimpanzees] about six years ago, I was on a trail by myself with a guide, and two female chimps came knuckle-walking by with babies on their backs. They were 2 feet [60 centimetres] from me. I began to think, how did Lucy carry her baby? Did she live in an environment like this? She lived in a troop maybe of 25 or 30 individuals. Did they make nests? I saw a nest that chimps make to sleep in. It all gave me a sense of the fossils coming to life.
The greatest fantasy that I have is: wouldn't it be fantastic if there had been visitors to our planet who came here 3.2 million years ago on a visit and shot video of what these creatures looked like?

Why are people so interested in Lucy?

I don’t know what it is about the name Lucy, but it's easy to remember. Children really gravitate towards this affectionate name she has, and that generates the view that this was an individual, that this was some person who actually lived. Perhaps even the fact that she's a female — we've been biased for so many years talking about  'evolution of man'. And she’s a touchstone and a centrepiece for the average person who is interested in answering that question that they've asked probably since they were a child: where did I come from? Lucy is that kind of ancestor that people like to identify with.

Prehistoric genomes reveal European origins of dogs

Continent's hunter-gatherers domesticated dogs from wolves some 20,000 years ago.
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Geneticists have sequenced DNA from fossil specimens such as this one in Greene County, Illinois, to reconstruct a family tree of modern dogs and understand where they were first domesticated.
European hunter-gatherers domesticated dogs from wolves around 20,000 to 30,000 years ago, concludes an analysis of DNA from fossils. The study — the largest collection of ancient dog and wolf DNA sequences yet published — is the latest installment in a long-running debate over canine domestication.
Scientists have squabbled over the timing and location of dog domestication for decades. The earliest dog-like fossils found so far are from Europe and Siberia and date to more than 30,000 years ago. Different genetic analyses of modern dogs and wolves have suggested that domestic dogs emerged in Europe, China or the Middle East anywhere from 10,000 to more than 30,000 years ago1–3.
DNA from early dogs and wolves has the potential to clear up the confusion, says Olaf Thalmann, an evolutionary geneticist at the University of Turku in Finland. He and his colleague Robert Wayne at the University of California, Los Angeles, belong to one of several groups seeking clarity from ancient dog genomes.

Thalmann and Wayne’s team sequenced the complete genomes of mitochondria — energy-producing cellular organelles that are inherited maternally — from a total of 18 ancient dogs and wolves ranging from 1,000 to 36,000 years old. The team created a family tree from these data, as well as from genetic information of modern dogs and wolves from around the world.
The tree pointed to a European origin for the domestic dog, Thalmann says. Nearly all modern dogs — from Australian Dingoes to a breed of hunting dog originally from central Africa called Basenji — share a close kinship with ancient dogs or wolves from Europe. The common ancestor of domestic dogs lived in Europe 18,800–32,100 years ago, Thalmann’s team reports today in Science4.

Distant relatives

However, two dog-like fossils, one from Belgium and one from Russia, were only distantly related to other ancient and modern dogs. At more than 30,000 years old, these bones represent the oldest dog-like fossils on record. Perhaps, Thalmann says, humans domesticated dogs from wolves multiple times, and these remains are the vestiges of ill-fated efforts.

Jean-Denis Vigne, an archaeo-zoologist at the National Museum of Natural History in Paris and CNRS, says it is possible that Europeans domesticated dogs more than once. But he adds that researchers still disagree over whether the Belgian and Russian fossils, which are much bigger than modern domestic canines, represent dogs or wolves.

Although Vigne has long contended, on the basis of the fossil evidence, that dogs emerged from Europe, he says the new study does not slam the door shut on other locales. The study did not look at ancient dogs from China or the Middle East.

Thalmann hopes to sequence samples from these areas, but believes the results would probably not alter the conclusion that domestication occurred in Europe. His team also hopes to examine DNA from the cell's nucleus in these and other fossils, which would yield much more information about ancestry than mitochondrial DNA. The researchers were unable to obtain enough quality nuclear DNA to be useful for the current study.

Greger Larson, an evolutionary geneticist at Durham University, UK, who studies animal domestication, says the new study stands out because it contains DNA sequences from a large number of ancient dogs and wolves, which “puts it on the path toward really figuring out the whole story of dog domestication”. With more ancient genomes coming, researchers studying dog domestication may soon have fewer bones to pick.