Top paleontology news stories of 2006
Filling in hominid gaps
Piecing together more than 4 million years of human evolution from a patchy fossil record is not an easy task. In 2006, however, anthropologists made great strides, filling in some significant gaps in that record.
Scientists unearthed a juvenile Australopithecus afarensis from 3.3 million years ago. The find stands as the earliest child hominid ever found. Photograph is by Zeresenay Alemseged; copyright by Authority for Research and Conservation of Cultural Heritages.
Earlier than 4 million years ago, the key hominid in human evolution was Ardipithecus. The early hominid likely walked upright, was only about the size of a chimpanzee, and had a small brain and large teeth. Australopithecus, the most famous specimen of which is “ Lucy,” hit the scene next, dominating hominids from about 4.4 million to 2 million years ago. Finally, that species is thought to have given rise to Homo, which has existed from 2 million years ago until now.
One find this year, reported in the April 13 Nature, bridges the gap between the early Ardipithecus and Australopithecus (see Geotimes, June 2006). Scientists determined that the bones, uncovered in Ethiopia, belong to Australopithecus anamensis. Dated at about 4.1 million years old, however, the find is separated from a species of the earlier Ardipithecus by only about 300,000 years, which poses the questions of exactly how, when and if Australopithecus branched off from Ardipithecus.
Also this year, paleontologists reported in the Sept. 21 Nature that they had uncovered fossils of a 3-year-old Australopithecus afarensis child. The find, nicknamed Lucy’s baby, is the earliest example of a child hominid ever found. Dated at 3.3 million years old (about 100,000 years older than Lucy), the remains support the notion that A. afarensis walked upright and had human-like hips, legs and feet, but retained ape-like shoulders, arms and hands that allowed it to take to the trees.
And finally, controversy continued over the status of the hominid remains of Homo floresiensis, first discovered in 2004 in a cave on the Indonesian island of Flores. Scientists continue to debate whether the small-sized hominids, called hobbits and thought to have lived until about 12,000 years ago, represent a new species, or were simply a pygmy version of Homo sapiens. This year, a team of researchers reported in the Aug. 23 Proceedings of the National Academy of Sciences that the pygmy was not a new species; rather, its small size was caused by microcephaly, a condition that leads to a small head and underdeveloped brain (see Geotimes online, Web Extra, Aug. 25, 2006).
New species or not, the hobbits’ small brains did not prevent them from making tools, according to Adam Brumm of the Australian National University. Tools found alongside the hobbits were similar to 800,000-year-old tools found 50 kilometers away. Publishing in the June 1 Nature, Brumm and colleagues suggested that the similarities indicate that the hobbits likely learned the tool-making skills from their ancestors Homo erectus.
On the hominid migration trail
Paleoanthropologists continued this year to fill in the missing pieces of a 50,000-year-old puzzle: how and why genetically and anatomically modern humans moved out of Africa. During the last few decades, advances in DNA studies increased scientists’ ability to better answer when, and by what route, early humans first migrated. This year, some researchers continued to seek answers by looking to clues from past environments.
Most scientists agree that modern human populations migrated from Africa to Eurasia about 40,000 to 60,000 years ago, but whether that dispersal occurred all at once or at multiple times remains heavily debated. Researchers have also pointed to a lack of genetic diversity among modern Europeans and Asians as evidence of a single dispersal event, according to Paul Mellars of the University of Cambridge.
In the Aug. 11 Science, Mellars wrote that archaeological evidence from tools found in eastern Africa also supports one large migration. Those tools, which have been dated to about the time of hominid dispersal, are similar in complexity and design to those found in southern Asia, which implies that southern Asia was likely the main, single migration route, he wrote.
Some scientists previously thought that humans’ migration path continued from southern Asia to Australasia. Here, evidence for the route becomes tenuous, as tools found in Australasia are simpler in design and technology than African tools. The difference, however, can be attributed to Australasia’s lack of high-quality stones such as flint, chert and obsidian, from which humans could construct advanced tools, Mellars reported.
A single migration route from Africa to southern Asia and on to Australasia would have most likely required hominids to migrate from Africa to Eurasia via a southern route, over the mouth of the Red Sea, Mellars says. Some researchers have suggested that a land bridge made such a migration possible.
But Carlos Fernandes of the biodiversity and ecological processes group at Cardiff University says that a Red Sea land bridge could not have existed at the time of migration. Publishing in the June 2006 Biogeography, Fernandes and colleagues estimated water depths of the Red Sea during the last 470,000 years, and concluded that sea levels would not have been low enough for a land bridge to have emerged.
If a land bridge indeed never existed over the Red Sea, then researchers will likely have to rethink how hominids dispersed from Africa, Fernandes reported. A northern route over the top of the Red Sea is another option, as is the southern route, if the early hominids were seafarers, Fernandes wrote.
Probing into fossil details
This year’s new fossil discoveries ran the usual gamut, from dinosaurs to bacteria. While the fossils themselves were familiar, however, paleontologists were armed with a suite of new ways to study them.
Bone histology proved particularly useful this year. Paleontologists can microscopically analyze ringed layers in dinosaur bones, which are similar to rings in the trunk of a tree, to get an idea about a dinosaur’s growth rate and age. The tool came in handy when Martin Sander, a paleontologist at the University of Bonn, and colleagues unearthed 11 sauropod dinosaur skeletons.
Most sauropods are known as behemoths, but these 11 sauropods were only one-quarter the size of a typical Brachiosaurus. Therefore, looking only at the bones’ size instead of at the layers, researchers likely would have concluded these specimens were juveniles.
But according to Sander, publishing in the June 8 Nature, bone histology showed that the small bones were fully developed, and that these specimens were adults of the new species Europasaurus holgeri (see Geotimes, August 2006). E. holgeri’s small size could be the result of island dwarfism — the phenomenon seen on islands today where a smaller animal will preferentially survive over a larger one when resources are scarce, the team wrote.
The ability to study dinosaur growth rates has provided researchers with “a new sense of the biology,” Thomas Holtz, a vertebrate paleontologist at the University of Maryland at College Park told Geotimes in August. In particular, researchers are finding that dinosaurs grow to full adult sizes very quickly, in contrast with modern reptiles. “They had rather fast growth rates, and that’s consistent with the idea that they had an elevated metabolism, much more like a bird or mammal than a crocodile or lizard,” Holtz said.
James Gillooly, a physiological ecologist at the University of Florida, and colleagues also used the bone analysis method to determine dinosaurs’ body temperatures. The team collected and applied growth rate data to an existing equation that estimates animal body temperatures (see Geotimes, September 2006). Based on the equation’s results, a small 12-kilogram dinosaur would have been a cool 25 degrees Celsius, implying a reptilian temperature regulation system that depended on the environment. A larger, almost 13-ton dinosaur, however, ran hot at 41 degrees Celsius — and likely had difficulty dissipating that heat. The results support previous ideas about how dinosaurs regulated their body temperatures.
Newly applied technologies also benefited scientists studying tiny fossils this year. William Schopf, a paleobiologist at the University of California in Los Angeles, and colleagues captured the first 3-D images of microscopic fossils by using an existing microscopy technology that allows fine structure to be examined without slicing, dicing and ruining the sample.
Combining images from the microscopy technique with another instrument that images chemical structure, the team looked at seven microfossils, including a spiral-shaped cyanobacteria, they reported in the January Astrobiology (see Geotimes, April 2006). The images resolved previously unseen details such as the thickness of cell walls, irregular patterns in cells and missing material. These new understandings may one day aid in the search for life on Mars, by helping researchers discern what is or is not a fossil, the authors reported.
On Earth however, a different 3-D imaging technique has already helped sleuth an evolutionary mystery. Philip Donoghue, a paleobiologist from the University of Bristol, and colleagues used X-ray tomographic microscopy to image the fossil embryo of Markuelia, a worm-like animal that lived 500 million years ago (see Geotimes, October 2006). The structure of teeth in the embryo helped the team place Markuelia as a relative to the modern-day penis worm, they reported Aug. 10 in Nature. Stay tuned, as “the technology is developing all the time,” Donoghue told Geotimes in October.
Evolution back in schools?
The controversy over how to present evolution to biology classes in Dover, Pa., is all but over. All eight members of the newly elected school board voted in January to officially remove mention of intelligent design (ID) — the concept that the complexity of life on Earth is evidence that something intelligent designed it — from classroom curricula.
The decision followed a December 2005 ruling in the federal case in which parents sued over the Dover Area School Board’s requirement that teachers read a statement about ID prior to discussions of evolution in biology classes. The judge ruled in favor of the parents, noting in a written statement that teachers may not “disparage the scientific theory of evolution” and also may not “refer to a religious, alternative theory known as ID,” (see Geotimes online, Web Extra, Dec. 20, 2005).
In Kansas, however, the state board of education is still hanging on to revised state science standards officially adopted in November 2005. The National Academy of Sciences and the National Science Teachers Association revoked copyright privileges for use of their materials, saying that the draft of those standards “distorts” the definition of science and emphasizes “controversy in the theory of evolution,” (see Geotimes, February 2006).
In November’s elections, two board members who voted for the antievolution standards retained their seats. Still, the board is expected in January to “rework” the standards, and “make them more pro-evolution oriented,” according to a Nov. 8 Associated Press story.
Despite the recent evolution-friendly decisions in Pennsylvania and Kansas, however, most adults in the United States remain wary of evolution. Specifically, during the last 20 years, the number of U.S. adults who accept evolution has dropped from 45 percent to 40 percent, according to a study by Jon Miller of Michigan State University and colleagues in the Aug. 11 Science. The same study found that in European countries such as Iceland, Denmark, Sweden and France, at least 80 percent of adults accept evolution.
Telling Tambora’s story: A profile of Haraldur Sigurdsson
Ask volcanologist Haraldur Sigurdsson to list the places around the world where his research has taken him, and you will soon find that you’d probably get a shorter answer by asking where it hasn’t taken him. In more than 40 years of research, Sigurdsson has studied volcanoes in places as diverse as Central America, South America, West Africa, North America, the Caribbean and Europe, including his native Iceland. He’s even been to the bottom of the sea to study submarine volcanoes on the Mid-Atlantic Ridge.
Volcanologist Haraldur Sigurdsson recovered numerous artifacts from Tambora, an Indonesian village that was buried by a volcanic eruption in 1815. Photograph is courtesy of the URI News Bureau.
Yet, of all the places he’s worked, Sigurdsson says his favorite is Mount Tambora, a 2,900-meter-high volcano on the Indonesian island of Sumbawa. “It’s sublime, it’s awe-inspiring,” says the University of Rhode Island professor, whose discovery of a lost village at the volcano garnered the attention of scientists and nonscientists alike this past year (see Geotimes, June 2006). “It’s like no other place I’ve been on Earth.”
Flanked by rainforest to the southwest and near-desert to the east, Mount Tambora is remote and thinly populated. That was not always the case, however: A little less than two centuries ago, the volcano was home to the kingdom of Tambora and more than 117,000 inhabitants, he says. Then, in 1815, Mount Tambora erupted in what is the largest volcanic eruption ever recorded, burying a village and spewing enough ash into the atmosphere to change global weather for years to come.
Although the eruption was 10 times larger than that of Indonesia’s infamous Krakatau volcano in 1883, it received far less attention because it occurred just “before the big media age,” Sigurdsson says. And because of Mount Tambora’s remote location, it was not as well studied.
So in 1986, and again in 1988, Sigurdsson set out to Mount Tambora to learn more about its spectacular eruption. While there, he says, he “became intrigued” by the volcano’s lost village, and sought to find it. The evening before the end of his second expedition, Sigurdsson asked a local guide if he knew of any pottery or other artifacts on the island.
“We had very little time because I had to catch a boat the next morning,” he says. With daylight waning, the guide led Sigurdsson to a gully where he saw carbonized trees, charcoal and pottery. “I realized this was a very interesting site,” he says, and resolved to come back.
And he did, although not until 16 years later, in 2004. But it was worth the wait: “As soon as we stuck the shovel in ground, I knew this was going to be something really amazing,” Sigurdsson says. “I had a tingling in my spine.” Soon, he and his colleagues were uncovering the wooden beams of a home, and finding artifacts such as china, bronze bowls and pottery. Sigurdsson had found Tambora.
“To unlock the secrets of Tambora is quite an accomplishment,” says Steven Carey, a former graduate student and current colleague of Sigurdsson at the University of Rhode Island. Carey says that Sigurdsson’s work not only sheds light on the eruption itself, but also provides insights into the way the people of Tambora lived. Like the ruins of Pompeii, the Italian city destroyed by the eruption of Mount Vesuvius in A.D. 79, Tambora offers a rich cultural snapshot where even the “mundane objects” of everyday life are preserved, Carey says.
Indeed, much of Sigurdsson’s work has focused on the human connection to volcanoes, and “spans the distance between science and art history and people,” says Dick Fiske, a geologist at the Smithsonian Institution in Washington, D.C., who has collaborated with Sigurdsson in the past. Sigurdsson says that he became fascinated by the effects of volcanoes on people while growing up in volcano-rich Iceland. That same fascination eventually led him to study places such as Tambora, Pompeii and Herculaneum — another city wiped out by Mount Vesuvius.
The work has not always been easy, however. Back in 1979, Fiske says, the helicopter he and Sigurdsson were riding in while studying Soufrière, a volcano on the island of St. Vincent in the West Indies, made a crash landing and was destroyed. Fortunately, the helicopter’s impact was cushioned by the soft soil of a freshly plowed field, and both researchers were able to walk away from the accident.
Carey says that Sigurdsson has “been tested on a number of occasions in Tambora,” too. During the 1986 expedition, Carey and Sigurdsson ran out of water and had to hike down the steep, unforgiving interior of the volcano to reach a lake. “We didn’t know if we’d be able to make it to the bottom,” Carey says. “It was touch-and-go in terms of survival.” The two did succeed and spent the next day hiking back out.
Despite the inherent risks of volcanology, Sigurdsson continues at it, driven by a great curiosity. “I like the opportunity to go out in nature and turn over every stone, look under it, and see what I find,” he says. “I like to hammer the rocks and see what secrets they have.”