SALT LAKE CITY, Dec. 10, 2009 – Did the first dinosaurs wander across continents or stay put where they first evolved? The first dinosaurs evolved 230 million years ago when the continents were assembled into one landmass called Pangea. The question of early dinosaur movements remained unclear until the discovery of some exciting new fossils.

Above: This is a fleshed-out reconstruction of the new Triassic carnivorous dinosaur Tawa hallae. Jorge Gonzalez.

In the Dec. 11, 2009, issue of Science, a team of paleontologists presents the 213-million-year-old fossils of previously unknown carnivorous dinosaur Tawa hallae, including several of the best preserved dinosaur skeletons from the Triassic Period.

Fossil bones of Tawa, named after the Hopi word for the Puebloan sun god, were recovered from a dig site in northern New Mexico known as Hayden Quarry. The quarry is located on Ghost Ranch, where late painter Georgia O’Keefe once lived. Fossil bones of several individuals were recovered, but the type specimen is a nearly complete skeleton of a juvenile that stood about 28 inches (70 centimeters) tall at the hips and was approximately 6 feet (about 2 meters) long, from snout to tail. Its body was about the size of a large dog, but with a much longer tail.

Based on an analysis of the relationships among Tawa and other early dinosaurs, the researchers hypothesize that dinosaurs originated in a part of Pangea that is now South America, diverging into theropods (like Tyrannosaurus rex), sauropodomorphs (like Apatosaurus) and ornithischians (like Triceratops); and then dispersed more than 220 million years ago across parts of Pangea that later became separate continents.

“This new dinosaur Tawa hallae changes our understanding of the relationships of early dinosaurs, and provides fantastic insight into the evolution of the skeleton of the first carnivorous dinosaurs” said Randall Irmis of the Utah Museum of Natural History and University of Utah, a co-author of the study.

In addition to Irmis, authors of the study included lead author Sterling Nesbit of the University of Texas at Austin; Nathan Smith of the University of Chicago and the Field Museum of Natural History; Alan Turner of Stony Brook University; Alex Downs of the Ruth Hall Museum of Paleontology in Abiquiu, N.M.; and Mark Norell of the American Museum of Natural History.

“If you have continents splitting apart, you get isolation,” said Nesbitt. “So when barriers develop, you would expect that multiple carnivorous dinosaurs in a region should represent a closely related endemic radiation. But that is what we don’t see in early dinosaur evolution.”

Instead, the research team found three distinct carnivorous dinosaurs – including the newly discovered Tawa – in the fossil-rich, Late Triassic beds they investigated at Ghost Ranch. “When we analyzed the evolutionary relationships of these dinosaurs, we discovered that they were only distantly related, and that each species had close relatives in South America,” said Irmis. “This implies that each carnivorous dinosaur species descended from a separate lineage before arriving in [the part of Pangea that is now] North America, instead of all evolving from a local ancestor.”

At Ghost Ranch, the researchers found fossils from a carnivorous dinosaur related to Coelophysis, common to that region, and fossils from a carnivore closely related to Herrerasaurus, which lived in South America. The 6.6- to 13-foot-long (2- to 4-meter-long) skeletons of Tawa display characteristics that exist in both species and features found in neither, implying a separate lineage.

“The discovery of multiple dinosaur species in one place that emigrated from elsewhere got us wondering whether other Late Triassic reptiles show similar patterns” said Irmis. “It turns out a variety of other reptile groups made multiple trips from the northern and southern continents [then parts of Pangea] and back again during the Late Triassic, including other dinosaurs.”

Because so many different groups with different life modes were able to move freely across Pangea, the research team concluded that during the Late Triassic, there were no major physical barriers, such as large mountain ranges, to the movement of reptiles between parts of Pangea that later separated into distinct continents.

But this presented a paradox to the team: “We wondered: if reptiles, including dinosaurs, were able to freely move around Pangea during the Late Triassic, then why aren’t there any sauropodomorph and ornithischian dinosaurs in North America during the Triassic?” said Irmis. “Our conclusion is that climate, possibly related to latitude, controlled the distributions of some reptile species.”

“We think that all the major dinosaur groups had the ability to get to North America [part of Pangea] during the Late Triassic, and may have even passed through, but for some reason, only the carnivorous dinosaurs found the North American climate to be hospitable during this time,” concluded Irmis.

The first Tawa fossils were discovered in 2004 by volunteers taking a paleontology seminar at the Ruth Hall Museum of Paleontology in New Mexico. Museum scientists invited the team of paleontologists to come and take a look.

“The specimens are unusual because they are so well preserved,” said Irmis. “Because dinosaur bones are hollow, they are usually broken and crushed, but those of Tawa are nearly pristine.”

Irmis and the rest of the team began a full-scale excavation in 2006 and have continued to unearth new material every summer since then. The fossil bone bed extends for tens of yards along a hillside, promising many years of potential significant finds.

BERKELEY — Researchers at the University of California, Berkeley, are challenging long-held beliefs that human beings are wired to be selfish. In a wide range of studies, social scientists are amassing a growing body of evidence to show we are evolving to become more compassionate and collaborative in our quest to survive and thrive.

Adult and child hands. Photo illustration by Jonathan Payne.

In contrast to “every man for himself” interpretations of Charles Darwin’s theory of evolution by natural selection, Dacher Keltner, a UC Berkeley psychologist and author of “Born to be Good: The Science of a Meaningful Life,” and his fellow social scientists are building the case that humans are successful as a species precisely because of our nurturing, altruistic and compassionate traits.

They call it “survival of the kindest.”

“Because of our very vulnerable offspring, the fundamental task for human survival and gene replication is to take care of others,” said Keltner, co-director of UC Berkeley’s Greater Good Science Center. “Human beings have survived as a species because we have evolved the capacities to care for those in need and to cooperate. As Darwin long ago surmised, sympathy is our strongest instinct.”

Keltner’s team is looking into how the human capacity to care and cooperate is wired into particular regions of the brain and nervous system. One recent study found compelling evidence that many of us are genetically predisposed to be empathetic.

The study, led by UC Berkeley graduate student Laura Saslow and Sarina Rodrigues of Oregon State University, found that people with a particular variation of the oxytocin gene receptor are more adept at reading the emotional state of others, and get less stressed out under tense circumstances.

Informally known as the “cuddle hormone,” oxytocin is secreted into the bloodstream and the brain, where it promotes social interaction, nurturing and romantic love, among other functions.

“The tendency to be more empathetic may be influenced by a single gene,” Rodrigues said.

While studies show that bonding and making social connections can make for a healthier, more meaningful life, the larger question some UC Berkeley researchers are asking is, “How do these traits ensure our survival and raise our status among our peers?”

Kindness crew passes out muffins to strangers(Photo illustration by Nick Stanger)
One answer, according to UC Berkeley social psychologist and sociologist Robb Willer is that the more generous we are, the more respect and influence we wield. In one recent study, Willer and his team gave participants each a modest amount of cash and directed them to play games of varying complexity that would benefit the “public good.” The results, published in the journal American Sociological Review, showed that participants who acted more generously received more gifts, respect and cooperation from their peers and wielded more influence over them.

“The findings suggest that anyone who acts only in his or her narrow self-interest will be shunned, disrespected, even hated,” Willer said. “But those who behave generously with others are held in high esteem by their peers and thus rise in status.”

“Given how much is to be gained through generosity, social scientists increasingly wonder less why people are ever generous and more why they are ever selfish,” he added.

Such results validate the findings of such “positive psychology” pioneers as Martin Seligman, a professor at the University of Pennsylvania whose research in the early 1990s shifted away from mental illness and dysfunction, delving instead into the mysteries of human resilience and optimism.

While much of the positive psychology being studied around the nation is focused on personal fulfillment and happiness, UC Berkeley researchers have narrowed their investigation into how it contributes to the greater societal good.

One outcome is the campus’s Greater Good Science Center, a West Coast magnet for research on gratitude, compassion, altruism, awe and positive parenting, whose benefactors include the Metanexus Institute, Tom and Ruth Ann Hornaday and the Quality of Life Foundation.

Christine Carter, executive director of the Greater Good Science Center, is creator of the “Science for Raising Happy Kids” Web site, whose goal, among other things, is to assist in and promote the rearing of “emotionally literate” children. Carter translates rigorous research into practical parenting advice. She says many parents are turning away from materialistic or competitive activities, and rethinking what will bring their families true happiness and well-being.

“I’ve found that parents who start consciously cultivating gratitude and generosity in their children quickly see how much happier and more resilient their children become,” said Carter, author of “Raising Happiness: 10 Simple Steps for More Joyful Kids and Happier Parents” which will be in bookstores in February 2010. “What is often surprising to parents is how much happier they themselves also become.”

As for college-goers, UC Berkeley psychologist Rodolfo Mendoza-Denton has found that cross-racial and cross-ethnic friendships can improve the social and academic experience on campuses. In one set of findings, published in the Journal of Personality and Social Psychology, he found that the cortisol levels of both white and Latino students dropped as they got to know each over a series of one-on-one get-togethers. Cortisol is a hormone triggered by stress and anxiety.

Meanwhile, in their investigation of the neurobiological roots of positive emotions, Keltner and his team are zeroing in on the aforementioned oxytocin as well as the vagus nerve, a uniquely mammalian system that connects to all the body’s organs and regulates heart rate and breathing.

Both the vagus nerve and oxytocin play a role in communicating and calming. In one UC Berkeley study, for example, two people separated by a barrier took turns trying to communicate emotions to one another by touching one other through a hole in the barrier. For the most part, participants were able to successfully communicate sympathy, love and gratitude and even assuage major anxiety.

Researchers were able to see from activity in the threat response region of the brain that many of the female participants grew anxious as they waited to be touched. However, as soon as they felt a sympathetic touch, the vagus nerve was activated and oxytocin was released, calming them immediately.

“Sympathy is indeed wired into our brains and bodies; and it spreads from one person to another through touch,” Keltner said.

The same goes for smaller mammals. UC Berkeley psychologist Darlene Francis and Michael Meaney, a professor of biological psychiatry and neurology at McGill University, found that rat pups whose mothers licked, groomed and generally nurtured them showed reduced levels of stress hormones, including cortisol, and had generally more robust immune systems.

Overall, these and other findings at UC Berkeley challenge the assumption that nice guys finish last, and instead support the hypothesis that humans, if adequately nurtured and supported, tend to err on the side of compassion.

“This new science of altruism and the physiological underpinnings of compassion is finally catching up with Darwin’s observations nearly 130 years ago, that sympathy is our strongest instinct,” Keltner said.

Homo floresiensis not diseased sub-population of healthy humans Researchers from Stony Brook University Medical Center in New York have confirmed that Homo floresiensis is a genuine ancient human species and not a descendant of healthy humans dwarfed by disease. Using statistical analysis on skeletal remains of a well-preserved female specimen, researchers determined the “hobbit” to be a distinct species and not a genetically flawed version of modern humans. Details of the study appear in the December issue of Significance, the magazine of the Royal Statistical Society, published by Wiley-Blackwell.

Above: New statistical analysis confirms that the recently discovered human-like “hobbit” also known as Homo floresiensis. The hobbit is a genuine ancient human species and not a descendant of healthy humans dwarfed by disease. (Credit: Image courtesy of Wiley-Blackwell)

In 2003 Australian and Indonesian scientists discovered small-bodied, small-brained, hominin (human-like) fossils on the remote island of Flores in the Indonesian archipelago. This discovery of a new human species called Homo floresiensis has spawned much debate with some researchers claiming that the small creatures are really modern humans whose tiny head and brain are the result of a medical condition called microcephaly.

Researchers William Jungers, Ph.D., and Karen Baab, Ph.D. studied the skeletal remains of a female (LB1), nicknamed “Little Lady of Flores” or “Flo” to confirm the evolutionary path of the hobbit species. The specimen was remarkably complete and included skull, jaw, arms, legs, hands, and feet that provided researchers with integrated information from an individual fossil.

The cranial capacity of LB1 was just over 400 cm, making it more similar to the brains of a chimpanzee or bipedal “ape-men” of East and South Africa. The skull and jawbone features are much more primitive looking than any normal modern human. Statistical analysis of skull shapes show modern humans cluster together in one group, microcephalic humans in another and the hobbit along with ancient hominins in a third.

Due to the relative completeness of fossil remains for LB1, the scientists were able to reconstruct a reliable body design that was unlike any modern human. The thigh bone and shin bone of LB1 are much shorter than modern humans including Central African pygmies, South African KhoeSan (formerly known as ‘bushmen”) and “negrito” pygmies from the Andaman Islands and the Philippines. Some researchers speculate this could represent an evolutionary reversal correlated with “island dwarfing.” “It is difficult to believe an evolutionary change would lead to less economical movement,” said Dr. Jungers. “It makes little sense that this species re-evolved shorter thighs and legs because long hind limbs improve bipedal walking. We suspect that these are primitive retentions instead.”

Further analysis of the remains using a regression equation developed by Dr. Jungers indicates that LB1 was approximately 106 cm tall (3 feet, 6 inches)—far smaller than the modern pygmies whose adults grow to less than 150 cm (4 feet, 11 inches). A scatterplot depicts LB1 far outside the range of Southeast Asian and African pygmies in both absolute height and body mass indices. “Attempts to dismiss the hobbits as pathological people have failed repeatedly because the medical diagnoses of dwarfing syndromes and microcephaly bear no resemblance to the unique anatomy of Homo floresiensis,” noted Dr. Baab.

Full Citation: “The geometry of hobbits: Homo floresiensis and human evolution.” William Jungers and Karen Baab. Significance; Published Online: November 19, 2009 (DOI: 10.1111/j.1740-9713.2009.00389.x); Print Issue Date: December 2009.

Caption: Paleontologist Paul Sereno with his Saharan discoveries — SuperCroc, BoarCroc (upper right), PancakeCroc (lower right), RatCroc, DogCroc and DuckCroc. The fossil crocs were unearthed in a series of expeditions to the Sahara beginning in 2000, supported by the National Geographic Society. Credit: Photo by Mike Hettwer, courtesy National Geographic.

Sereno, a professor at the University of Chicago, and his team unearthed the strange crocs in a series of expeditions beginning in 2000 in the Sahara. Many of the fossils were found lying on the surface of a remote, windswept stretch of rock and dunes. The crocs galloped and swam across present-day Niger and Morocco when broad rivers coursed over lush plains and dinosaurs ruled.

“These species open a window on a croc world completely foreign to what was living on northern continents,” Sereno said. The five crocs, along with a closely related sixth species, will be detailed in a paper published in the journal ZooKeys and appear in the November 2009 issue of National Geographic magazine. The crocs also will star in a documentary, “When Crocs Ate Dinosaurs,” to premiere at 9 p.m. ET/PT Saturday, Nov. 21, on the National Geographic Channel.

At 40 feet in length and weighing 8 tons, Sarcosuchus imperator, popularly known as SuperCroc, was the first and largest of the crocs Sereno found in the Sahara, but it was not the strangest, Sereno said. He and his teams soon discovered key fossils of five previously unknown or poorly understood species, most of them walking “upright” with their arms and legs under the body like a land mammal instead of sprawled out to the sides, bellies touching the ground.

The crocs and their nicknames:

• BoarCroc: New species, Kaprosuchus saharicus; fossils found in Niger. Twenty-foot-long upright meat eater with an armored snout for ramming and three sets of dagger-shaped fangs for slicing. Closest relative found in Madagascar.
• RatCroc: New species, Araripesuchus rattoides; fossils found in Morocco. Three-foot-long, upright plant and grub eater. Pair of buckteeth in lower jaw used to dig for food. Closest relative in South America.
• PancakeCroc: New species, Laganosuchus thaumastos; fossils found in Niger and Morocco. Twenty-foot-long, squat fish eater with a three-foot pancake-flat head. Spike-shaped teeth on slender jaws. Likely rested motionless for hours, its jaws open and waiting for prey. Closest relative from Egypt. The scientific paper also names a close relative discovered by the team in Morocco, Laganosuchus maghrebensis.
• DuckCroc: New fossils of previously named species, Anatosuchus minor. Fossils found in Niger. Three-foot-long upright fish-, frog- and grub-eater. Broad, overhanging snout and Pinocchio-like nose. Special sensory areas on the snout end allowed it to root around on the shore and in shallow water for prey. Closest relative in Madagascar.
• DogCroc: New fossils of named species, Araripesuchus wegeneri. Fossils found in Niger include five skeletons, all next to each other on a single block of rock. Three-foot-long upright plant and grub eater with a soft, doglike nose pointing forward. Likely an agile galloper, but also a capable swimmer. Closest relative in Argentina.

“We were surprised to find so many species from the same time in the same place,” said paleontologist Hans Larsson, associate professor at McGill University in Montreal and a team member who discovered the bones of BoarCroc and PancakeCroc. “Each of the crocs apparently had different diets, different behaviors. It appears they had divided up the ecosystem, each species taking advantage of it in its own way.”

To better understand how these ancient crocs — mostly upright and agile — might have moved and lived, Sereno traveled to northern Australia, where he observed and captured freshwater crocs. Realizing while there that he may have stumbled onto one of the keys to crocodilian success, Sereno saw freshwater crocs galloping at full speed on land and then, at water’s edge, diving in and swimming away like fish. On land they moved much like running mammals, yet in a flash turned fishlike, their bodies and tails moving side to side, propelling them in water.

Based on interpretation of the fossils, Sereno and Larsson hypothesize that these early crocs were small, upright gallopers. In the scientific paper, they suggest that the more agile of their new croc menagerie could not only gallop on land but also evolved a swimming tail for agility and speed in water, two modes of locomotion suggested to be evolutionary hallmarks for the past 200 million years.

“My African crocs appeared to have had both upright, agile legs for bounding overland and a versatile tail for paddling in water,” Sereno writes in the National Geographic magazine article. “Their amphibious talents in the past may be the key to understanding how they flourished in, and ultimately survived, the dinosaur era.”

To study the crocs’ brains, Sereno CT-scanned the skulls of DuckCroc and DogCroc and then created digital and physical casts of the brains. The result: Both DogCroc and DuckCroc had broad, spade-shaped forebrains that look different from those of living crocs. “They may have had slightly more sophisticated brain function than living crocs,” Larsson said, “because active hunting on land usually requires more brain power than merely waiting for prey to show up.”

To collect the croc fossils, Sereno and his teams endured temperatures topping 125 degrees F, living for months on dehydrated food. Logistics were challenging: For the 2000 expedition, they transported trucks, tools, tents, five tons of plaster, 600 pounds of water and four months’ worth of other supplies.

The evolutionary history of New Zealand’s many extinct flightless moa (Aves: Dinornithiformes) has been re-written in the first comprehensive study of more than 260 sub-fossil specimens to combine all known genetic, anatomical, geological and ecological information about the unique bird lineage. The authors used mitochondrial phylogenetic information from subfossil moa specimens from across NZ with morphological, ecological, and new geological data to create the first comprehensive phylogeny, taxonomy, and evolutionary timeframe for all of the species of an extinct order.

Above: Moas were flightless birds, some of which evoved large body sizes. Today, the Kiwi is thought to be their closest living relative.
That lineage ended only about 600 years ago after a journey through time that most likely began about 80 million years earlier on the prehistoric supercontinent of Gondwana, according to the study published in Proceedings of the National Academy of Sciences by an international team of researchers.

Found on the south and north islands of New Zealand, the evolutionary history and relationships between the moa species has long been subject to scientific debate, with past studies suggesting that up to 64 species existed with as many as 20 generic groups.

The new study found that moas should be grouped into only three families, six genera and it reduced the number of species to nine. The most recent species were relatively modern, evolving in the South Island only after the uplift of the Southern Alps between 5 and 8.5 million years ago.

Periodical land bridges, created by geological events and sea-level changes, allowed some of these species to cross over to the North Island.

The many species of moa are thought to have descended from a common ancestor of other large living flightless birds that evolved on separate southern landmasses when Gondwana broke up: the ostrich in Africa; the emu and cassowary in Australia; the rhea in South America; and New Zealand’s kiwi. Another presumed relative was the extinct giant elephant bird in Madagascar.

New Zealand broke away from Gondwana at least 60 million years ago and a wide variety of moas subsequently evolved there, ranging in size from a large turkey to the three-metre tall Dinornis, which weighed up to 300 kg.

Maori people are known to have killed large numbers of birds for their meat, eggs and feathers — moa is a Polynesian word for chicken — after they arrived on the islands about 1,000 years ago. All the nine living species were gone within a few centuries.

The study also presents an important new geological/paleogeographical model, which suggests that land-dwelling animals on the North and South Island landmasses were isolated for most of the past 20-30 million years.

“The prolonged geographic isolation of New Zealand and the paucity of terrestrial mammals created a unique ecosystem dominated by an estimated 245 species of birds, providing an unparalleled opportunity to observe evolutionary processes,” says Dr Trevor Worthy, a palaeontologist from the UNSW School of Biological, Earth and Environmental Sciences, who was one of the 11 members of study team.

“Our study reveals that the patterns of genetic diversity within and between different moa groups reflect a complex history following a major drowning of the New Zealand landmass in the Oligocene [23 to 34 million years ago]. Their history was then affected by a series of marine barriers, tectonic activity and glacial cycles.

“We were surprised to discover just how recently many of the moa species — and probably many of the iconic New Zealand animals and plants — evolved in the South Island after the uplift of the Alps. The Alps brought rain and allowed wet rainforests to develop in the west and generated a drier, warmer climate to the east, creating a mix of upland and lowland environments, wet and dry habitats and a variety of forest, shrubland, and grasslands.”

Full citation: Bunce, M et al. 2009. The evolutionary history of the extinct ratite moa and New Zealand Neogene paleogeography
PNAS published online before print November 18, 2009, doi:10.1073/pnas.0906660106

Nov. 11, 2009 — Were dinosaurs “warm-blooded” like present-day mammals and birds, or “cold-blooded” like present day lizards? The implications of this simple-sounding question go beyond deciding whether or not you’d snuggle up to a dinosaur on a cold winter’s evening.

In a study published this week in the journal PLoS ONE, a team of researchers, including Herman Pontzer, Ph.D., assistant professor of anthropology in Arts & Sciences, has found strong evidence that many dinosaur species were probably warm-blooded.

If dinosaurs were endothermic (warm-blooded) they would have had the potential for athletic abilities rivalling those of present day birds and mammals, and possibly similar quick thinking and complicated behaviours as well. Their internal furnace would have enabled them to live in colder habitats that would kill ectotherms (cold-blooded animals), such as high mountain ranges and the polar regions, allowing them to cover the entire Mesozoic landscape. These advantages would have come at a cost, however; endothermic animals require much more food than their ectothermic counterparts because their rapid metabolisms fatally malfunction if they cool down too much, and so a constant supply of fuel is required.

Pontzer worked with colleagues John R. Hutchinson and Vivian Allen from the Structure and Motion Laboratory at the Royal Veterinary College in England to bring a combination of simple measurements, rigorous computer modeling techniques and their knowledge of physiology in present-day animals to bear in a new study on this hot topic. Using their combined experience, the authors set out to determine whether a variety of dinosaurs and closely related extinct animals were endothermic or ectothermic, and when, where and how often in the dinosaur family tree this important trait may have evolved.

Above: Estimates from our V_musc-based method for slow walking (Fr 0.25) used to reconstruct the evolution of endothermy. Substantial size-related homoplasy is shown. B. Estimates from our hip height-based method for moderate running (Fr 1.0) as a less conservative alternative to Fig. 2A. Endothermy is estimated as ancestral for at least Dinosauriformes.

“It’s exciting to apply our studies of living animals back to the fossil record to test different evolutionary scenarios,” Pontzer said. “I work on the evolution of human locomotion, using studies of living humans and other animals to figure out the gait and efficiency of our earliest fossil ancestors. When I realized this approach could be applied to the dinosaur record, I contacted John Hutchinson, an expert on dinosaur locomotion, and suggested we collaborate on this project. Our results provide strong evidence that many dinosaur species were probably warm-blooded. The debate on this issue will no doubt continue, but we hope our study will add a useful new line of evidence.”

Studies of present-day animals have shown that endothermic animals are able to sustain much higher rates of energy use (that is, they have a higher “VO2max”) than ectothermic animals can. Following this observation, the researches reasoned that if the energy cost of walking and running could be estimated in dinosaurs, the results might show whether these extinct species were warm- or cold-blooded. If walking and running burned more energy than a cold-blooded physiology can supply, these dinosaurs were probably warm-blooded.

But metabolism and energy use are complex biological processes, and all that remains of extinct dinosaurs are their bones. So, the authors made use of a recent work by Pontzer showing that the energy cost of walking and running is strongly associated with leg length - so much so that hip height (the distance from the hip joint to the ground) can predict the observed cost of locomotion with 98% accuracy for a wide variety of land animals. As hip height can be simply estimated from the length of fossilized leg bones, Pontzer and colleagues were able to use this to obtain simple but reliable estimates of locomotor cost for dinosaurs.

To back up these estimates, the authors used a more complex method based on estimating the actual volume of leg muscle dinosaurs would have had to activate in order to move, using methods Hutchinson and Pontzer had previously developed. Activating more muscle leads to greater energy demands, which may in turn require an endothermic metabolism to fuel. Estimating active muscle volume in an extinct animal is a great deal more complicated than measuring the length of the legs, however, and so the authors went back to basic principles of locomotion.

First, how large would the forces required from the legs have to be to move the animal? In present-day animals, this is mainly determined by how much the animal weighs and what sort of leg posture it uses - straight-legged like a human or bent-legged like a bird, for example. Second, how much muscle would be needed to supply these forces? Experiments in biological mechanics have shown that this depends mainly on the limb muscles’ mechanical advantage, which in turn depends strongly on the size of the bony levers they are attached to.

To apply these principles to extinct dinosaurs, Pontzer and colleagues examined recent anatomical models of 13 extinct dinosaur species, using detailed measurements of the fossilized bony levers that limb muscles attached to. From this, the authors were able to reconstruct the mechanical advantage of the limb muscles and calculate the active muscle volume required for each dinosaur to walk or run at different speeds. The cost of activating this muscle was then compared to similar costs in present-day endothermic and ectothermic animals.

The results of both the simple and complex method were in very close agreement: based on the energy they consumed when moving, many dinosaurs were probably endothermic, athletic animals because their energy requirements during walking and running were too high for cold-blooded animals to produce. Interestingly, when the results for each dinosaur were arranged into an evolutionary family tree, the authors found that endothermy might be the ancestral condition for all dinosaurs. This pushes the evolution of endothermy further back into the ancient past than many researchers expected, suggesting that dinosaurs were athletic, endothermic animals throughout the Mesozoic era. This early adoption of high metabolic rates may be one of the key factors in the massive evolutionary success that dinosaurs enjoyed during the Triassic, Jurassic and Cretaceous periods, and continue to enjoy now in feathery, flying form.

Their methods add to the many lines of evidence, from bone histology to lung ventilation and insulatory “protofeathers,” that are all beginning to support the fundamental conclusion that dinosaurs were generally endothermic. Ironically, indirect anatomical evidence for active locomotion in dinosaurs was originally some of the first evidence used by researchers John Ostrom and Robert Bakker in the 1960s to infer that dinosaurs were endothermic.

Pontzer and his colleagues provide a new perspective on dinosaur anatomy, linking limb design to energetics and metabolic strategies. The debate over dinosaur physiology will no doubt continue to evolve, and while the physiology of long-extinct species will always remain a bit speculative, the authors hope the methods developed in this study provide a new tool for researchers in the field.

AUSTIN, Texas — Breaking up may actually not be hard to do, say scientists who’ve found a population of tropical butterflies that may be on its way to a split into two distinct species.

Above: Polymorphic mimicry in Heliconius cydno alithea in western Ecuador, where the white form (middle left) mimics the white species Heliconius sapho (top left) and the yellow form (middle right) mimics the yellow species Heliconius eleuchia (bottom right). Image: Marcus Kronforst and Krushnamegh Kunte

The cause of this particular break-up? A shift in wing color and mate preference.

In a paper published this week in the journal Science, the researchers describe the relationship between diverging color patterns in Heliconius butterflies and the long-term divergence of populations into new and distinct species.

“Our paper provides a unique glimpse into the earliest stage of ecological speciation, where natural selection to fit the environment causes the same trait in the same population to be pushed in two different directions,” says Marcus Kronforst, a Bauer Fellow in the Center for Systems Biology at Harvard University who received his doctor’s degree at The University of Texas at Austin. “If this trait is also involved in reproduction, this process can have a side effect of causing the divergent subpopulations to no longer interbreed. This appears to be the process that is just beginning among Heliconius butterflies in Ecuador.”

Heliconius butterflies display incredible color pattern variation across Central and South America, with closely related species usually sporting different colors. In Costa Rica, for example, the two most closely related species differ in color: One species is white and the other is yellow. In addition, both species display a marked preference to mate with butterflies of the same color.

The Ecuadorian population examined by Kronforst and his colleagues shows the same white and yellow variation found in Costa Rica but has not yet reached a level of strong reproductive isolation. The entire population lives in close proximity and individuals of both colors come in contact with–and mate with–each other.

But, by studying the Ecuadorian population in captivity, the scientists found the two colors do not mate randomly. Despite the genetic similarity between the groups–white and yellow varieties differ only at the color-determining gene–yellow Ecuadorian individuals show a preference for those of the same color. White male butterflies, most of which are heterozygous at the gene that controls color, show no color preference.

Above: The yellow and white forms of Heliconius cydno alithea from western Ecuador. Photos: Lawrence Gilbert

“This subtle difference in mate preference between the color forms in Ecuador may be the first step in a process that could eventually result in two species, as we see in Costa Rica,” says Kronforst, who began studies of Heliconius color pattern and behavioral genetics in the laboratory of Professor Lawrence Gilbert at The University of Texas at Austin.

Previous studies of species formation have focused on the characteristics of well-differentiated species, and the health and viability of their hybrids in particular, in an effort to identify how the species may have emerged and how they stay distinct.

Heliconius provides a model for a different kind of study. The researchers considered species emergence from the opposite end, studying populations that have yet to diverge into separate species in order to identify the role of mate choice in the potential emergence of new species.

Having identified color-based mate preference in Heliconius, the researchers used a battery of genetic markers to compare the genomes of the white and yellow varieties, showing that they are genetically identical except for their different colors and preferences.

Their work suggests that the genes for color and preference are very close to one another in the genome; the two traits could even be caused by the same gene. Their next step is to identify the gene (or genes) responsible for the differences in color and mate preference.

“If we can identify this gene or genes, we can say conclusively how they influence both color and mate choice,” says Kronforst. “Subsequent work could elucidate exactly how changes in individual genes can, over long periods of time, lead to novel species.”

“This study shows the great potential of the genus Heliconius as a model system for integrating genetics, development, behavior, ecology and evolution,” says Gilbert, professor in the Section of Integrative Biology. “It is the culmination of diverse contributions of the co-authors involving insectary, field and laboratory research over more than a decade.”

Co-authors on the Science paper with Kronforst are Nicola L. Chamberlain and Ryan I. Hill, both of Harvard; Durrell D. Kapan of the University of Hawaii; and Lawrence E. Gilbert of The University of Texas at Austin. Their work was funded by the National Science Foundation and the National Institutes of Health.

Scientists have an ambitious new strategy for untangling the evolutionary history of humans and their biological relatives: a genetic menagerie made of the DNA of more than 10,000 vertebrate species. The plan, proposed by an international consortium of scientists, is to obtain, preserve, and sequence the DNA of approximately one species for each genus of living mammals, birds, reptiles, amphibians, and fish.

Above: Scientists involved in the Genome 10K Project are sampling specimens of thousands of animals spanning a broad range of evolutionary diversity.These species will have their entire genomes sequenced. Credit: Photos courtesy of San Diego Zoo.

“Understanding the evolution of the vertebrates is one of the greatest detective stories in science,” said David Haussler, a Howard Hughes Medical Institute investigator at the University of California, Santa Cruz (UCSC). “No one has ever really known how the elephant got its trunk, or how the leopard got its spots. This project will lay the foundation for work that will answer those questions and many others.”

“Understanding the evolution of the vertebrates is one of the greatest detective stories in science.”
David Haussler

Known as the Genome 10K Project, the approximately $50 million initiative is “tremendously exciting science that will have great benefits for human and animal health,” Haussler said. “Within our lifetimes, we could get a glimpse of the genetic changes that have given rise to some of the most diverse life forms on the planet.”

Haussler is one of the lead authors of an article, published online November 5, 2009, in the Journal of Heredity, that outlines the project. The other lead authors include Stephen J. O’Brien, chief of the Laboratory of Genomic Diversity at the National Cancer Institute, and Oliver A. Ryder, director of genetics at the San Diego Zoo’s Institute for Conservation Research and adjunct professor of biology at the University of California, San Diego. Coauthors and additional authors, who together make up a group called the Genome 10K Community of Scientists (G10KCOS), include geneticists, paleontologists, ecologists, conservationists, and other scientists representing major zoos, museums, research centers, and universities around the world.

The proposal originated at a meeting Haussler hosted at UCSC in April 2009. More than 50 scientists came together to discuss the merits of the project and its daunting logistic and financial challenges. “Some of the people at the meeting were initially skeptical,” Haussler said. “But they quickly recognized the many advantages of a shared infrastructure and data analysis system.”

The primary impetus behind the proposal is the rapidly expanding capability of DNA sequencers and the associated decline in sequencing costs. “We’ll soon be in a situation where it will cost only a few thousand dollars to sequence a genome,” Haussler said. “At that point, most of the cost will be getting samples, managing the project, and handling data.”

All living vertebrates descend from a single marine species that lived 500-600 million years ago. Paleontologists do not know much about the physical appearance of that species, but because all of its descendents share certain characteristics, they know that it had segmented muscles, a forebrain, midbrain, and hind brain attached to spinal cord structures, and a sophisticated innate immune system.

That primitive vertebrate gave rise to what Haussler calls “one of the most spectacularly malleable branches of life.” Vertebrates spread throughout the oceans, conquered land, and eventually took to the air. Over the course of time they produced stunning innovations, including multichambered hearts, bones and teeth, an internal skeleton that has supported the largest aquatic and terrestrial animals on the planet, and a species of primate — Homo sapiens — that has produced sophisticated language, culture, and technology.

By sequencing the DNA of 10,000 vertebrates — roughly one-sixth of the 60,000 species estimated to be living today — biologists will be able to reconstruct the genetic changes that gave rise to this astonishing diversity. Some parts of our DNA are very similar to the DNA of other vertebrates, reflecting our descent from a common ancestor, while other parts are markedly different. “We can understand the function of elements in the human genome by seeing what parts of the genome have changed and what parts have not changed in humans and other animals,” said Haussler.

The project also will help conservation efforts by documenting the genomes and genetic diversity of threatened and endangered vertebrate species. By helping scientists predict how species will respond to climate change, pollution, emerging diseases, and invasive competitors, it will support the assessment, monitoring, and management of biological diversity.

The G10KCOS consortium has been developing guidelines for the collection, preservation, and documentation of cell lines and DNA samples. It also has been discussing potential public and private sources of funding for the project — estimated at $50 million if the price of handling and sequencing each DNA sample eventually falls to $5,000. Said Haussler: “How do you raise $50 million? Ask nicely and make a strong case.”

In planning the project, the G10KCOS group has used the Human Genome Project as a model. For example, the consortium plans to release sequencing data immediately according to standards developed for the sequencing of the human genome. Haussler also cited that project, which began before needed sequencing technologies were available, as evidence that it is worthwhile to begin planning for the Genome 10K Project before the cost of sequencing falls enough to make it feasible. “The time to start is now, or the job will get away from us,” said Haussler. “The sequencing machines will be waiting, but the samples won’t be ready.”

The legendary “man-eating lions of Tsavo” that terrorized a railroad camp in Kenya more than a century ago likely consumed about 35 people–far fewer than popular estimates of 135 victims, according to a new analysis led by researchers at the University of California, Santa Cruz. The study also yields surprises about the predatory behavior of lions.

Above, Left: New research yields surprising differences in the diets of two male Tsavo lions that rampaged a camp more than a century ago. Photo of modern Tsavo lions courtesy of Bruce Patterson. Right: Lt. Col. John Patterson beside one of the man-eating lions he shot in 1898. Photo courtesy The Field Museum/Z93658.

Despite the notoriety of the attacks–the harrowing nine-month saga has been the subject of three Hollywood films, and the lions remain a popular exhibit at the Field Museum of Natural History in Chicago–the number of victims has been a matter of dispute. The new study, “Cooperation and Individuality Among Man-Eating Lions,” appears in the Nov. 2 issue of the Proceedings of the National Academy of Sciences. The research utilized a sophisticated stable-isotope analysis to investigate this vexing question.

By analyzing samples of the hair and bone of the lions, researchers were able to estimate that one lion likely ate 11 humans and the other consumed 24 people during the animals’ final nine months. Both lions were shot and killed in December 1898 by Lt. Col. John H. Patterson, a British officer and engineer hired to restore safety in the region. For years after, Patterson, who gained great notoriety for the feat, claimed the lions had killed 135 people–far more than the Ugandan Railway Company’s estimate of 28 victims.

“This has been a historical puzzle for years, and the discrepancy is now finally being addressed,” said Nathaniel J. Dominy, an associate professor of anthropology at UCSC. “We can imagine that the railroad company might have had reasons to want to minimize the number of victims, and Patterson might have had reasons to inflate the number. So who do you trust? We’re removing all those factors and getting down to data.”

Dominy and lead author Justin D. Yeakel, a doctoral candidate in ecology and evolutionary biology at UCSC, collaborated on the project with Bruce D. Patterson, the MacArthur Curator of Mammals at the Field Museum (no relation to John H. Patterson).

To investigate each lion’s lifetime dietary patterns, Yeakel analyzed samples of their bone collagen and hair keratin that were provided by the Field Museum. He then compared those data to the isotopic signatures of the lions’ presumptive prey, including modern grazing and browsing animals, and humans. Human samples were obtained from the remains of Kenya’s Taita population that were gathered by anthropologist Louis Leakey during his famous East African Archaeological Expedition of 1929.

The results suggest that during the final months of what John Patterson described as the lions’ “reign of terror,” fully half of one lion’s diet consisted of humans, with the balance made up of mid-sized grazing animals such as gazelles and impala. Strikingly, the other lion ate very few humans, subsisting instead on herbivores. That dietary disparity leads Dominy and Yeakel to infer that the Tsavo lions worked together to scatter everyone, both humans and wild game, setting the stage for one to gorge on humans and the other to feed on herbivores.

“The idea that the two lions were going in as a team yet exhibiting these dietary preferences has never been seen before or since,” said Dominy.

Cooperative hunting is beneficial when lions are stalking large prey like Cape buffalo and zebra, but humans are small enough that lions don’t typically need to work together to make a kill. In this case, an array of conditions may have temporarily altered the lions’ behavior, including drought and disease that depleted the availability of the lions’ conventional prey. In addition, large numbers of people and animals had gathered for the railroad project, and severe dental problems and a jaw injury suffered by one of the lions probably greatly inhibited its ability to hunt.

“These findings underscore the complexity of what lions are capable of doing, and the complex interplay of costs and benefits that determine the size of their coalitions,” he said.

The stark dietary differences highlight the importance of considering individuals within populations, said Yeakel. “In ecology, we often think of a population as being the sum of its parts, but there can be really rich things happening among individuals in a population,” he said. “It’s a new way of thinking about how populations work to consider how individuals affect the whole.”

More than a century after the attacks, the Tsavo lions remain notorious; last year, the National Museum of Kenya began an effort to recover the remains of the lions, saying they represent an important part of the country’s history and heritage. The grisly chapter finally ended in December 1898, when John Patterson–after nine months spent in pursuit of the animals–shot and killed one lion, then killed the second lion 20 days later. During the final three months of the nine-month siege, lion attacks were a “nightly occurrence,” and work on the railroad expansion had ground to a halt as terrified laborers refused to work, said Dominy, noting that the delay prompted the first and only mention of lions in Britain’s House of Parliament as members demanded an explanation for the work stoppage.

Ending the terror earned John Patterson widespread and enduring fame, but Dominy wonders if the boastful hunter might have exaggerated his estimate of victims to enhance his own reputation. “The railroad company attributed the deaths of 28 Indian nationals to the lions, and Patterson may have reasonably assumed scores of Africans were also killed,” said Dominy. “But based on our statistical analysis, there’s an outside chance they ate as many as 75 people. Our evidence attests only to the number of people eaten, not the number of people killed.”

In 1924, John Patterson sold the hides of the lions–which he had used as rugs–to the Field Museum, where taxidermists restored and stuffed the pelts and mounted a diorama that continues to fascinate museum visitors today. Patterson’s 1907 book, The Man-Eaters of Tsavo, was an international bestseller when it was published, and it remains in print today.

“The fact that we can determine both the diet and the behavior of two animals killed more than a century ago is a testament to the enduring value of museum collections and the science that interprets them,” said Field Museum curator Bruce Patterson. “The rather extravagant claims (Colonel) Patterson made in his book can now be pretty much dismissed.”

For Dominy, downgrading the number of human victims of the Tsavo lions is the latest chapter in a legend that takes a new turn with the insights about lion predation offered by these animals. The path of human evolution has been shaped by predation, said Dominy, noting that the efficiency benefits of bipedalism are gained at the cost of speed, making humans vulnerable to quick, four-legged predators, including lions.

“In a discussion of bipedalism, Louis Leakey once said, ‘People are not cat food,’ ” said Dominy. “But they are. This study proves that.”

Ever since the Falklands wolf was described by Darwin himself, the origin of this now-extinct canid found only on the Falkland Islands far off the east coast of Argentina has remained a mystery. Now, researchers reporting in the November 3rd issue of Current Biology who have compared DNA from four of the world’s dozen or so known Falklands wolf museum specimens to that of living canids offer new insight into the evolutionary ancestry of these enigmatic carnivores.

Falkland wolf (Dusicyon australis).  Credit: Darwin, C. R. ed. 1838. Mammalia Part 2 No. 1 of The Zoology of the Voyage of H.M.S. Beagle. By George R. Waterhouse. Courtesy of Wikimedia Commons)

“One of the big draws for an evolutionary biologist is that this species had a big influence on Darwin’s ideas about how species evolve,” said Graham Slater of the University of California, Los Angeles, noting that Darwin recognized differences between the East Falkland and West Falkland wolves as evidence that species are not fixed entities. But the wolves’ circumstances were also just downright puzzling.

“It’s really strange that the only native mammal on an island would be a large canid,” Slater explained. “There are no other native terrestrial mammals—not even a mouse. It’s even stranger when you consider that the Falklands are some 480 kilometers from the South American mainland. The question is, how did they get there?”

Possible explanations for the wolves’ presence on the islands, which have never been connected to the South American mainland, range from dispersal by ice or logs to domestication and subsequent transport by Native Americans. Ultimately, the Falklands wolf died out because it was perceived as a threat to settlers and their sheep, although fur traders took out a lot of the population as well.

Biologists have also puzzled over the Falklands wolf’s ancestry. It had been suggested that they were related to domestic dogs, North American coyotes, or South American foxes. Slater said the wolves were the size of a coyote, but much stockier, with fur the color of a red fox. They had short muzzles, just like gray wolves, and thick, wooly fur.

Slater’s team now reports that the Falklands wolf’s closest living relative is actually the maned wolf—an unusually long-legged, fox-like South American canid. The researchers also found that the four Falklands wolf samples that they examined shared a common ancestor at least 70,000 years ago, which suggests that they arrived on the islands before the end of the last ice age and before humans ever made it into the New World. That rules out the prevailing theory that Native Americans had anything to do with their presence on the islands.

“The biggest surprise was that the divergence of the Falklands wolf from its closest living relative, the maned wolf, occurred over 6 million years ago,” Slater said. “Canids don’t show up in the South American fossil record until 2.5 million years ago, which means these lineages must have evolved in North America. The problem is that there are no good fossils that can be assigned to the Falklands wolf lineage in North America.”

Given that maned and Falklands wolves split so long ago, there should be fossils of their close relatives in South America, Slater said. And in fact, the researchers may have a candidate: a species from Patagonia called Dusicyon avus, which went extinct 6,000 to 8,000 years ago. Slater says that’s a possibility that study coauthor Alan Cooper at the University of Adelaide in Australia is further investigating now.