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Tools of the trade. Artist's drawing of a possible shaman burial, found near the Sea of Galilee.

Credit: P. Groszman (illustration drawn to scale)

Before there were priests or doctors, people seeking solace or treatment for an illness often called in a shaman, an intermediary between the human and spirit worlds. Archaeologists working in Israel now claim that a 12,000-year-old grave of a woman buried with various animal and human body parts is that of an early shaman. If true, it could mean that shamanism arose during a critical period in human cultural evolution.

Although largely supplanted by organized religion, shamanism is still widespread in Asia, Africa, Europe, and the Americas. For example, many Eskimo groups around the Arctic Circle practice shamanism. The roots of shamanism reach back at least to the ancient Greeks and possibly even to prehistoric times. Many archaeologists assume that shamanism preceded organized religion, and some see depictions of shamans in cave art from 15,000 years ago or earlier--although that interpretation is controversial.

But recent excavations at Hilazon Tachtit, a cave west of the Sea of Galilee in Israel, may provide new support for prehistoric shamanism. Hilazon Tachtit was occupied by the Natufians, a people who inhabited the Near East between about 15,000 and 11,500 years ago. Most archaeologists see Natufian culture as a transition between hunting and gathering and the sedentary lifestyles of early farmers. At Hilazon Tachtit, a team led by archaeologist Leore Grosman of the Hebrew University of Jerusalem has found the remains of at least 25 people, most in collective burials. But one was treated differently. A woman, about 45 years old when she died and whose pelvis and spine were deformed, was buried separately, accompanied by a menagerie of animal remains. Among her grave goods were tail bones from wild cattle, a wing bone from a golden eagle, the shells of 50 tortoises, and a large foot from another person.

The team, which reports its findings online today in the Proceedings of the National Academy of Sciences, notes that tortoises, cow tails, and eagle wings play a role in the ritualistic practices of many shamans today and that many societies ascribe special powers to physically disabled people. "It seems that the woman in the Natufian burial was perceived as being in a close relationship with these animal spirits," the authors write. They suggest that shamanism either sparked, or was the result of, the cultural upheavals that accompanied the agricultural revolution in the Near East.

"This is an extremely important report on a rare find at a critical time of cultural evolution," says Brian Hayden, an archaeologist at Simon Fraser University in Burnaby, Canada. Ian Kuijt, an anthropologist at the University of Notre Dame in South Bend, Indiana, adds that the "authors have done an excellent job of supporting their argument" for prehistoric shamanism. But Mina Evron, an archaeologist at the University of Haifa in Israel, cautions that there may be alternative explanations, though she doesn't offer one herself. Just because the team's "colorful interpretation" seems plausible, she says, "it ain't necessarily so."

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Prehistoric toothache. These ancient teeth from Japan show tooth decay, which is more common in fertile women.

Credit: Daniel H. Temple University/University of Missouri

The old wives’ tale that a woman loses one tooth for every child she delivers may, in fact, contain a grain of truth. A new study has found that women have had worse dental health than men ever since our ancestors became farmers about 10,000 years ago. That wasn't just because their diets and eating habits changed, as researchers previously believed, but because women who settled on farms were more fertile than nomadic hunter-gatherers. A boost in fertility meant farmers' wives were pregnant more often, which caused changes in their hormones and saliva secretion that rotted their teeth, according to a report in this month's issue of Current Anthropology.

Researchers have known since the 1980s that the invention of agriculture led to more tooth decay, particularly in women. Most researchers have attributed this to dietary and cultural changes that come from settling down. Both men and women began eating more starchy grains, such as corn and wheat, which contain sugars. Changes in the division of labor meant that women were preparing food more than men--and snacking more, because they had access to more food. "You increase carbohydrates and generally you increase the incidence of dental caries," says anthropologist Clark Spencer Larsen of Ohio State University in Columbus.

The shift to farming also set in motion other important biological changes, notes biological anthropologist John Lukacs of the University of Oregon in Eugene. Lukacs did a meta-analysis of studies of tooth decay in 147 collections of tens of thousands of teeth from prehistoric and living humans that lived around the world from 12,000 years ago to 800 years ago. He confirmed that women consistently had more cavities than men when they lived in agricultural societies. He also documented a rise in fertility among women, perhaps in part because they were less nomadic and didn't have to carry children from place to place. Women would have experienced three other factors that occur during pregnancy and increase the number of cavities in women: a boost in female sex hormones; a reduction in the flow rate of saliva and its antimicrobial properties; and an increase in cravings for high-energy, sweet foods.

This comprehensive view of women's oral health is "very smart," says dentist and geneticist Alexandre Vieira of the University of Pittsburgh in Pennsylvania. How much being pregnant contributes to cavities could be tested, says Larsen, by comparing the incidence of tooth decay in women and men in modern populations before and after boosts in fertility. Lukacs agrees: "Our new task is to partition the factors that cause caries--how much is caused by biology and how much by culture," he says. "It's not all or nothing--it's a mixture."

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Southern exodus. A trail of stone tools and fossil bones suggests that early humans left Africa 1.8 million years ago. Some headed north to Dmanisi, Georgia; others may have taken a southern route into China and Java, Indonesia.

Credit: NASA/TerraMetrics/Human Origins Program, Smithsonian

Over a million years ago, a band of early humans left their stone tools and two front teeth near a stream in southwest China. For decades, the precise age of the fossils has remained a mystery, leaving open a central question in paleontology: How quickly did our human ancestors reach China after leaving Africa? Now, thanks to advanced dating techniques, scientists may finally have the answer.

Chinese paleontologists discovered the two incisors in 1965 and the relatively simple stone tools in 1973 in the Yuanmou Basin. The teeth came from a hominin, the group that includes humans and our exclusive ancestors, and might be from the species Homo erectus, a direct ancestor of humans that may have been the first human to spread beyond Africa about 1.8 million years ago. Scientists have gotten mixed results for the age of the site because there were no volcanic crystals in the soils for reliable radiometric dating. Lacking solid dates, researchers thought until a decade ago that the earliest humans didn't reach Asia until 1 million years ago. But a series of dates for fossils from one site in Java, Indonesia, in particular, have recently shown that Homo erectus was there 1.66 million years ago and possibly earlier. This changed the old textbook view that human ancestors spread around the globe only after they had big brains and more advanced stone hand axes, which appear in Africa about 1.6 million years ago.

Now, a team of Chinese and American researchers has redated the Yuanmou Basin site using a paleomagnetic technique that relies on rock samples to determine the direction of Earth's magnetic field when the rocks were formed. Although the original hillside where the fossils were found has been excavated, the discoverers recorded the layer of sediment where they uncovered the teeth and tools. The new team traced that sediment layer--or time horizon--throughout the basin, collecting 318 rock samples from it. In an article in press in the Journal of Human Evolution, the researchers report that the fossils came from a layer of rock just above a magnetic landmark known as the Olduvai-Matuyama reversal boundary, which is at least 1.77 million years old. This makes the fossil site slightly younger, about 1.7 million years old.

This age estimate represents "the oldest definite fossil and archaeological evidence of early hominins in China and mainland East Asia," says co-author Rick Potts, a paleoanthropologist at the Smithsonian Institution in Washington, D.C. The finds are a bit younger than the oldest Homo erectus fossils from western Asia, which are 1.77 million years old and come from Georgia, and a bit older than the most conservative dates for the Java remains and 1.66-million-year-old stone tools from northeast China. Taken together, these dates from at least three fossil sites are convincing many researchers that early humans were moving rapidly across Asia 1.77 million to 1.66 million years ago. "What's so important about this paper is that we finally have good, solid paleomagnetic dates," says paleoanthropologist Susan Antón of New York University in New York City. "I think the body of data for early Homo in China is getting much stronger."

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Bone to pick.
Carbon dating of ancient rat bones (like the jaw bone shown) suggests that humans first arrived in New Zealand in 1280 or later.

Credit: Janet Wilmshurst/Landcare Research

Rats caught a free ride to New Zealand when they hopped aboard the boats of early Polynesian explorers. Now, their ancient bones may help pinpoint when humans first set foot on the island. Carbon-dating of bones from the rodents indicates that people reached New Zealand around 1280 or later, rejecting previous research that suggested humans may have landed there more than 1400 years earlier.

Although most anthropologists think that humans first arrived in New Zealand around 1250 to 1300, a minority holds that people might have set foot on the island as early as 200 B.C.E. That conclusion is based on 1996 research that carbon-dated bones of rats, which are thought to have been brought to New Zealand by humans either as stowaways or for food. But this study has been controversial because there's no evidence of human settlements at that time. Some critics have suggested that the carbon dates were due to a lab error in preparing the bones.

To help clear up the confusion, a team led by Janet Wilmshurst, a paleoecologist at environmental research organization Landcare Research in Lincoln, New Zealand, used a different preparation technique that is thought to be more accurate. The researchers obtained 17 bones from the two excavation sites where the oldest rat remains had been found. Carbon-dating with the improved method indicated that the new bones were from 1280 or later. When the researchers tried the new technique on some of the bones from the previous study, all of them dated to later than 1280, indicating that the earlier research was flawed. The researchers next carbon-dated ancient seeds that the rats had gnawed and that came from one of the excavation sites. The results gave a date of 1290 or later, confirming that humans did not arrive until 1280 at the earliest, the researchers report in the 3 June issue of the Proceedings of the National Academy of Sciences.

Ian Smith, an anthropologist at the University of Otago in New Zealand, says the finding "provides convincing evidence against the assertion that either rats or people reached New Zealand prior to the 13th century A.D." He adds that the later arrival indicates that humans' devastating impact on New Zealand, which has included deforestation and the extinction of birds and marine mammals, happened in only 600 years, versus more than 2000 years if the initial bone dating had been confirmed.

David Lowe, a soil scientist at the University of Waikato in Hamilton, New Zealand, says the findings also indicate that "the destruction caused by the rats in New Zealand has been pronounced and very fast indeed." The rats wiped out several species, including some birds and frogs. Wilmshurst adds that the speed of destruction "makes the risk to currently declining populations of rat-sensitive species more pressing as they could be diminishing faster than previously assumed."

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Premodern?
The shell of this fossil turtle may predate the ancestor of modern turtles.

Credit: (fossil) Juliana Sterli/Biology Letters (turtle) Jorge A.Gonzalez (2008)

As reptiles go, turtles are old--no question. They evolved before snakes and crocodiles and preceded dinosaurs. But establishing when the common ancestor of modern turtles first appeared has recently become controversial. Now a new fossil is backing the idea that modern turtles evolved more recently than previously thought.

Living turtles are divided into two main groups--the Cryptodira and the Pleurodira--based on where on the skull the muscles that close the lower jaw are attached. In the 1970s, paleontologist Eugene Gaffney of the American Museum of Natural History (AMNH) in New York City conducted the first modern analysis of turtle evolution. He proposed that almost all fossil turtles belonged within one or the other of these two modern, or crown, groups. That meant that the common ancestor of these turtles first appeared in the Late Triassic, some 210 million years ago.

Last year, paleontologist Walter Joyce of Yale University outlined a major revision of this classification. After reviewing all of the anatomical features, called characters, of the fossil turtles, he argued in the Bulletin of the Peabody Museum of Natural History that many of the fossil taxa were so different from modern turtles that they don't belong in either the Cryptodira or the Pleurodira groups. The implication is that these two groups only evolved about 150 million years ago. "Joyce's picture of turtle evolution is totally different," says James Parham of the California Academy of Sciences, who is based in Santa Barbara.

The new fossil backs this picture, say Joyce and Parham. It comes from Argentina and was discovered in central Patagonia by a joint expedition of the Museo Paleontológico Egidio Feruglio in Trelew and AMNH. About 35 centimeters long, the fossils of a shell and skull were found in ancient lake rocks, dating to between 160 million and 146 million years old--a period in which turtle fossils are few and far between. Juliana Sterli, a Ph.D. student at the Museo de Historia Natural de San Rafael in Mendoza, Argentina, set about describing and analyzing the fossil, which has been named Condorchelys antiqua. Sterli says her research shows that Condorchelys doesn't belong to the Cryptodira or Pleurodira and fits Joyce's hypothesis that the modern groups are at least 60 million years younger than previously thought.

"It's an important fossil," Gaffney says. "A discovery like this gives an important ... glimpse of early Jurassic turtles" in South America. But Gaffney thinks that the turtle fits within his original classification scheme--as a primitive Cryptodira--and is not evidence for Joyce's reinterpretation of turtle evolution. Sterli disagrees, based on analyses of anatomical details. If Joyce and Sterli are correct, Parham notes, then modern turtles would have taken much less time to evolve.

Related site

• Overview of Gaffney's history of turtle evolution

Coal mine canaries?
A decline in the health and diversity of coral-like bryozoans could signal impending environmental disaster.

Credit: Shane Anderson/NOAA

Some of the mass extinctions in Earth's long history resulted from catastrophic events such as asteroid impacts or massive volcanic eruptions. But two researchers who have studied the fossil remains of coral-like marine creatures during two of the biggest of these die-offs argue that prolonged environmental stress might have wiped out many species more quietly. The findings could help scientists predict the effects of climate change on today's marine life.

The demise of the dinosaurs and other species 65 million years ago is well known, but it was preceded by two even bigger mass extinctions. The Great Dying, as scientists call it, ended the Permian period 250 million years ago by killing off 90% of marine creatures and 70% of the land dwellers. The Triassic extinction about 200 million years ago exterminated 20% of Earth's marine life and half the terrestrial species--while allowing dinosaurs eventually to flourish. In both cases, there's no evidence for an asteroid impact or volcanic conflagration, so the causes of the events remain unresolved.

It's possible those two great extinctions actually occurred gradually over millions of years and were caused by steady deterioration of the global environment. At least, that's what the research--the most comprehensive of its kind--by paleontologists Catherine Powers and David Bottjer of the University of Southern California in Los Angeles suggests. After combing through 396 collections of fossil bryozoans--bottom-dwelling animals that resemble corals and live in colonies--the researchers report in this month's issue of Geology that the number of species declined steadily and slowly. Powers says she thinks their fossil record should be "a good proxy for studying the environmental effects of these mass extinctions."

Powers says that chemical analyses done elsewhere suggest the bryozoans' decline accompanied a gradual increase in the carbon dioxide content of the oceans, possibly caused by undersea volcanic eruptions. Regardless of the source, the increase could represent a bellwether for adverse environmental changes, such as increasing acidification of seawater or declining oxygen levels. Powers says the next step in the research will be to pinpoint when the bryozoans started declining, to see if the start of the trends can be isolated. That would give scientists better ideas about when to look for specific triggering events, such as plate tectonics or volcanic eruptions, in the geologic record. So far, she says, the declining bryozoan diversity can only be analyzed in blocks representing millions of years.

The paper shows how long-term environmental stress could have led to the two mass extinctions, says paleoecologist Margaret Fraiser of the University of Wisconsin, Milwaukee. The data suggest that "large-scale environmental and ecological changes have occurred in Earth's history and were facilitated by increased CO₂ levels," she says, which gives researchers "much to learn about the present and future from the geologic record."

Related sites

• More about bryozoans
• The Permian-Triassic extinction
• The Triassic-Jurassic boundary

Testimonial.
Ancient teeth hold clues to early hominid diets.

Credit: Science

The robust australopithecines of South Africa are often described as failed humans, having died out 1 million to 1.4 million years ago. Researchers believe their high-fiber, low-nutrient diets might have been too specialized to allow them to cope with a changing environment. A new report in tomorrow's issue of Science challenges this assumption, however, arguing that these close cousins of humans were much more culinarily adventurous than thought.

With their huge molars and massive jaw muscles, australopithecines have been portrayed as nutcrackers who crunched their way through seeds, nuts, and pulpy fruits. As Africa grew cooler and drier, however, these critical fall-back foods were hard to come by, supposedly leading to the hominid's downfall.

To test this theory, a team of American and British researchers studied the teeth of four individuals of Paranthropus robustus (also known as Australopithecus robustus) from the Swartkrans Cave in South Africa. The team scanned the teeth with a sensitive laser, which did not destroy the teeth but etched them lightly enough to free carbon gases long trapped in the enamel. Because different plants absorb atmospheric carbon dioxide differently, the researchers were able to see what types of vegetation the hominids ate based on the ratio of carbon isotopes in their teeth.

Their cuisine included a mix of tropical grasses and sedges, along with woody fruits, shrubs, and herbs, according to the findings. What's more, carbon samples from ridges laid down like tree rings in a single tooth revealed that the hominids switched between these diverse plants, depending on the time of year. The pattern held, regardless of when the hominids lived. Although the specimens date back to about 1.8 million years ago, each individual's lifetime was probably separated by thousands or tens of thousands of years, indicating that Paranthropus robustus was quite capable of dealing with changes in climate or different habitats. "We didn't expect to see as much variability as we found," says lead author Matt Sponheimer of University of Colorado at Boulder. "It was quite a surprise."

The new method is a huge improvement over old isotopic studies that required anthropologists to drill--and destroy--teeth to sample carbon, like prehistoric dentists, says paleoanthropologist Fred Grine of the Stony Brook University in New York. "Sponheimer's taken the analysis of carbon isotopes in fossils to a new level of sophistication," he says, adding that he hopes that fossil teeth--and diets--of earlier hominids can also be studied with the new nondestructive method.

Related sites

• For more on Paranthropus robustus
• For more on isotopic analysis to reconstruct diet

Survivor.
A newly discovered rodent species belongs to a family thought to have been extinct for 11 million years.

Credit: Mark A. Klinger

A rodent family long thought to exist only in fossilized remains turns out to be very much alive. This example of the "Lazarus effect," when an animal group known only from the fossil record reemerges thanks to the discovery of a living member, gives "invaluable insights" into our planet's biodiversity, past and present, researchers report 10 March in Science.

A few years ago, scientists surveying the biodiversity of Southeast Asia noticed an unfamiliar rodent that resembled a squirrel being sold as food in a Laotian marketplace. Apparently nocturnal, it lives in rocky limestone and thick vegetation and had stayed hidden from scientists for centuries. The team reported their find--a new species, genus, and family--in 2005. But to a group of paleontologists, led by Mary Dawson of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, the rodent looked quite familiar. Upon reading descriptions of it, Dawson remembers thinking, "this is something we've known from the fossil record since 1974." Members of the family--called Diatomyidae--hadn't scampered on Earth for 11 million years, but Dawson had more than a hunch that the new rodent was part of the clan.

To confirm her suspicions, Dawson and colleagues compared several physical characteristics of the new rodent, dubbed Laonastes aenigmamus, to those of Diatomyidae. The teeth and jaws of these ancient rodents bore a striking resemblance to Laonastes. The positioning of the lower jaw, for example, was nearly identical, indicating a similar type of chewing motion. And the tooth enamel of old and new shared unusual patterns not found in other rodent species. Dawson says finding a living example of a fossilized family will help clear up some questions that bones can't always answer, such as how the rodents moved and what they ate.

The Lazarus finding is "very novel," says paleomammalogist Ross MacPhee of the American Museum of Natural History in New York City. "You really don't expect these creatures you work on to suddenly come to life again." MacPhee and paleontologist Lawrence Flynn of Harvard University both emphasize that the study underlines the importance of conserving ecological hot spots like the one where Laonastes was found in Southeast Asia. "It's another reason why we should be examining biodiversity today," says Flynn. "It's not true that, 'Gosh, everything's been discovered.'"

Related sites

• Biodiversity in Laos by the numbers
• All about rodents