Sunday, March 23, 2008

Upright Walking Began 6 Million Years Ago, Thigh Bone Comparison Suggests

ScienceDaily (Mar. 21, 2008) — A shape comparison of the most complete fossil femur (thigh bone) of one of the earliest known pre-humans, or hominins, with the femora of living apes, modern humans and other fossils, indicates the earliest form of bipedalism occurred at least six million years ago and persisted for at least four million years. William Jungers, Ph.D., of Stony Brook University, and Brian Richmond, Ph.D., of George Washington University, say their finding indicates that the fossil belongs to very early human ancestors, and that upright walking is one of the first human characteristics to appear in our lineage, right after the split between human and chimpanzee lineages. Their findings are published in the March 21 issue of the journal Science.
The research is the first thorough quantitative analysis of the Orrorin tugenensis fossil – a fragmentary piece of femur – which was discovered in Kenya in 2000 by a French research team. Dr. Jungers, Chair of Anatomical Sciences at SBU School of Medicine, and Dr. Richmond, Associate Professor of Anthropology at GWU and a member of GWU’s Center for the Advanced Study of Hominid Paleobiology, completed a multivariate analysis of the proximal femora shape of a young adult O. tugenensis that enabled them to pinpoint the pattern of bipedal gait for this controversial hominin. Their analysis included a large and diverse sample of apes, other early hominins, including Australopithecus, and modern humans of all body sizes.
“This research solidifies the evidence that the human lineage split off as far back as six million years ago, that we share ancestry with Orrorin, and that our ancestors were walking upright at the time,” says Dr. Richmond. “These answers were not clear before this analysis.”
“Our study confirms that as early as six million years ago, basal hominins in Africa were already similar to later australopithecines in their anatomy and inferred locomotor biomechanics,” adds Dr. Jungers. “At the same time, by way of the analysis, we see no special phylogenetic connection between Orrorin and our own genus, Homo.”
In “Orrorin tugenensis Femoral Morphology and the Evolution of Hominin Bipedalism,” the authors articulate that the analysis and morphological comparisons among femora from the fossils showed that O. tugenensis is distinct from those of modern humans and the great apes in having a long, anteroposteriorly narrow neck and wide proximal shaft. Early Homo femora have larger heads and broader necks compared to early hominins. In addition to these features, modern human femora have short necks and mediolaterally narrow shafts.
The challenge ahead, explains Dr. Jungers, is “to identify what precipitated the change from this ancient and successful adaptation of upright walking, and climbing, to our own obligate form of bipedalism.”
Adapted from materials provided by Stony Brook University Medical Center.

Fausto Intilla

Ancient Lemur's Little Finger Poses Mystery

ScienceDaily (Mar. 22, 2008) — Analysis of the first hand bones belonging to an ancient lemur has revealed a mysterious joint structure that has scientists puzzled.
Pierre Lemelin, an assistant professor of anatomy at the University of Alberta in Edmonton, Canada, and a team of fellow American researchers have analyzed the first hand bones ever found of Hadropithecus stenognathus, a lemur that lived 2,000 years ago.
The bones were discovered in 2003 in a cave in southeastern Madagascar, an island nation off the coast of Africa in the Indian Ocean. Hadropithecus is related to the modern-day sifaka, a type of lemur with acrobatic leaping skills. A lemur is a monkey-like animal with a long tail and large eyes.
An examination of the five tiny hand bones by Lemelin and the rest of the research team revealed a never-before-seen hand joint configuration on the side of the little finger. The same joint configuration is straight in all other primates, including Archaeolemur, a close extinct relative of Hadropithecus.
"Our analysis showed a mosaic of lemurid-like, monkey-like and very unique morphological traits," Lemelin said. "Because the joint was present on both hands, it's likely not an anomaly, but because there are no other Hadropithecus hand bones for comparison, we don't know for certain," Lemelin said. "It is a mystery, and further investigation is needed to explain the difference in this species."
Lemelin and his colleagues from George Washington University, the Medical College of Georgia, and the universities of Stony Brook and Massachusetts at Amherst, also discovered that, unlike its close living relatives, Hadropithecus lacked anatomical traits linked with wrist mobility and strong finger flexion that characterize primate species that climb or cling to trees.
The hand bones also showed that Hadropithecus had very short thumbs and was a quadrupedal species, walking on all fours, much like many primates, such as baboons, do today. The discovery underscores the amazing diversity of lemurs that existed more than 2,000 years ago, when lemurs of all types ranged from pocket-sized to the size of gorillas, Lemelin noted.
The findings were published this month in the Journal of Human Evolution.
The study was funded by the Natural Sciences and Engineering Research Council of Canada and The Leakey Foundation.
Adapted from materials provided by University of Alberta, via EurekAlert!, a service of AAAS.

Fausto Intilla

New Zealand's 'Living Dinosaur' -- The Tuatara -- Is Surprisingly The Fastest Evolving Animal

ScienceDaily (Mar. 23, 2008) — In a study of New Zealand's "living dinosaur" the tuatara, evolutionary biologist, and ancient DNA expert, Professor David Lambert and his team from the Allan Wilson Centre for Molecular Ecology and Evolution recovered DNA sequences from the bones of ancient tuatara, which are up to 8000 years old. They found that, although tuatara have remained largely physically unchanged over very long periods of evolution, they are evolving - at a DNA level - faster than any other animal yet examined.
"What we found is that the tuatara has the highest molecular evolutionary rate that anyone has measured," Professor Lambert says.
The rate of evolution for Adélie penguins, which Professor Lambert and his team have studied in the Antarctic for many years, is slightly slower than that of the tuatara. The tuatara rate is significantly faster than for animals including the cave bear, lion, ox and horse.
"Of course we would have expected that the tuatara, which does everything slowly -- they grow slowly, reproduce slowly and have a very slow metabolism -- would have evolved slowly. In fact, at the DNA level, they evolve extremely quickly, which supports a hypothesis proposed by the evolutionary biologist Allan Wilson, who suggested that the rate of molecular evolution was uncoupled from the rate of morphological evolution."
Allan Wilson was a pioneer of molecular evolution. His ideas were controversial when introduced 40 years ago, but this new research supports them.
Professor Lambert says the finding will be helpful in terms of future study and conservation of the tuatara, and the team now hopes to extend the work to look at the evolution of other animal species.
"We want to go on and measure the rate of molecular evolution for humans, as well as doing more work with moa and Antarctic fish to see if rates of DNA change are uncoupled in these species. There are human mummies in the Andes and some very good samples in Siberia where we have some collaborators, so we are hopeful we will be able to measure the rate of human evolution in these animals too."
The tuatara, Sphendon punctatus, is found only in New Zealand and is the only surviving member of a distinct reptilian order Sphehodontia that lived alongside early dinosaurs and separated from other reptiles 200 million years ago in the Upper Triassic period.
Journal reference: Lambert et al.:"Rapid molecular evolution in a living fossil." Researchers include Jennifer M. Hay, Sankar Subramanian, Craig D. Millar, Elmira Mohandesan and David M. Lambert, Trends in Genetics. March 2008. (
Adapted from materials provided by Cell Press, via EurekAlert!, a service of AAAS.
Fausto Intilla

Good Luck Indeed: 53 Million-year-old Rabbit's Foot Bones Found

ScienceDaily (Mar. 24, 2008) — One day last spring, fossil hunter and anatomy professor Kenneth Rose, Ph.D. was displaying the bones of a jackrabbit's foot as part of a seminar at the Johns Hopkins University School of Medicine when something about the shape of the bones looked oddly familiar.
That unanticipated eureka moment has led researchers at the school to the discovery of the oldest known record of rabbits. The fossil evidence in hand, found in west-central India, predates the oldest previously known rabbits by several million years and extends the record of the whole category of the animal on the Indian subcontinent by 35 million years.
Published online in the February Proceedings of the Royal Society, the investigators say previous fossil and molecular data suggested that rabbits and hares diverged about 35 million years ago from pikas, a mousy looking member of the family Ochotonidae in the order of lagomorphs, which also includes all of the family Leporidae encompassing rabbits and hares.
But the team led by Johns Hopkins's Rose found that their rabbit bones were very similar in characteristics to previously unreported Chinese rabbit fossils that date to the Middle Eocene epoch, about 48 million years ago. The Indian fossils, dating from about 53 million years ago, appear to show advanced rabbit-like features, according to Rose.
"What we have suggests that diversification among the Lagamorpha group-all modern day hares, rabbits and pikas-may already have started by the Early Eocene," says Rose, professor in the Center for Functional Anatomy and Evolution at the Johns Hopkins University School of Medicine.
Rose says the new discovery was delayed a few years because the researchers had not been looking specifically to determine the age of rabbits. "We found these bones on a dig in India a few years ago and didn't know what animal they came from, so we held onto them and figured we'd look at them later," he says. "It didn't occur to us they would be rabbits because there were no known rabbits that early in time and the only known rabbits from that part of the world are from central Asia."
But one day, while using the jackrabbit foot bones as a teaching tool for a class, the shape of the bones in the class struck him as something he'd seen before among his collection of unidentified bones.
Sure enough, the tiny bones about a quarter of an inch long from India looked remarkably similar to ankle and foot bones from modern day jackrabbits, which are 4 to 5 times bigger.
Rose and his team set out and measured every dimension of their Indian bones and compared them to eight living species of rabbits and hares. They also compared them to two species of the related pika-that mouse-like, mountain-dwelling critter that lives in the Rocky Mountains of North America, among other places.
Using a technique called character analysis, the team first recorded measurements of 20 anatomical features of the bones, which showed that the bones are definitely Lagomorph and closer to rabbits than pikas. The scientists then ran a series of statistical tests on the individual measurements to see how they compared with the Chinese fossils as well as living rabbits and pikas. They found that although the Indian fossils resemble pikas in some primitive features, they look more like rabbits in specialized bone features.
Asked how many years of good luck one gets with a 53 million-year-old rabbit foot bone, Rose quipped that he "already got lucky with the feet, but what we really would like are some teeth that tell how different these animals really were."
The research was funded by the National Geographic Society, Department of Science and Technology, Government of India, the Council for Scientific and Industrial Research of India, the Research Foundation Flanders and the Belgian Federal Science Policy Office.
Authors on the paper are Valerie Burke DeLeon and Rose of Hopkins; Pieter Missiaen of University of Ghent, Belgium; R.S. Rana and Lachham Singh of H.N.B. Garhwal University in Uttaranchal, India; Ashok Sahni of Panjab University, India; and Thierry Smith of the Royal Belgian Institute of Natural Sciences in Brussels, Belgium.
Adapted from materials provided by Johns Hopkins Medical Institutions, via EurekAlert!, a service of AAAS.

Fausto Intilla