Dr. Semprebon Among Scientists Providing New Evidence on Human Evolution
LONGMEADOW, MA. — Scientists working in the Afar Rift, Ethiopia—among them, Bay Path College Professor of Biology and Chair of Science and Mathematics Gina M. Semprebon, PhD—have published new results of a 17-year investigation of the 4.4 million-year-old hominid Ardipithecus ramidus in the October 2 special issue of the journal Science.
The results open a new chapter on human evolution by extending knowledge into a previously poorly known period, only a few million years after the human line diverged from that leading to chimpanzees. The findings reveal the kind of human ancestor that came before the better-known "ape-man" Australopithecus, until now the most completely known early hominid genus thanks to fossils like the skeleton of "Lucy" discovered in Ethiopia in 1974. The new fossils reveal the early evolutionary steps that our ancestors took after we diverged from our common ancestor with chimpanzees.
The centerpiece discovery is a 4.4 million-year-old partial skeleton of a female nicknamed "Ardi." The team recovered important parts of the skeleton including the skull with teeth, arms, hands, pelvis, legs, and feet. This is now the earliest skeleton known from the human branch of the primate family tree. Our branch constitutes the zoological family "Hominidae;" "hominids" include Homo sapiens as well as all species closer to humans than to chimpanzees and bonobos, our closest living relatives. The discoveries provide new insights into how hominids might have emerged from a more primitive ancestral form.
In addition to her role at Bay Path, Dr. Semprebon currently serves as a principal investigator in the paleoecology research for the National Science Foundation’s Revealing Hominid Origins Initiative (RHOI) Program, which provided funding for research. Dr. Semprebon is well known in the scientific community for her research in paleoecology—the study of ancient ecosystems and their organisms, which reveals natural characteristics of ancient history, such as environments, climates, temperatures, and vegetation among other aspects. As a paleontologist, she is internationally recognized for the co-cultivation of the stereomicrowear technique, which enables scientists to identify the diets of fossil mammals by examining microscopic scars on dental enamel caused by food substances. Dr. Semprebon and her colleagues reconstructed Ardi’s diet and studied her food preference and survival requirements.
By examining the scars of Ardi’s smaller teeth, especially her low-rounded molar cusps, Dr. Semprebon and her team discovered that like most large-bodied primates, Ardi likely consumed both animal, vegetable and fruit substances.
Dr. Semprebon’s research also enabled her to reconstruct Ardi’s ancient habitat and ecology. Instead of African grasslands, the data demonstrated that the landscape was dominated by woodlands. Ardi’s environment comprised fresh water springs and patches of dense forests and included fig and hackberry trees. Ardi shared her habitat with land snails, owls, parrots, mice, porcupines, and elephants, among other animals.
This information ultimately will enable Dr. Semprebon and other scientists to investigate long-term environmental trends, such as global warming and cooling. They can also trace morphological changes in mammals, focusing specifically on their dietary shifts and the ability to move independently from one location to another.
Through Dr. Semprebon’s and her colleagues’ research, scientists can now discern in much greater detail the basic steps in our evolution from ancient forms. The details of our evolutionary past increasingly show the complex interrelationship of environmental change, habitat transformation, and biological adaptation. All indications are that our biological and social roots are evolutionarily deep. Ardipithecus bridges the early gap between Australopithecus and more ancient forms, and shows that chimpanzees, bonobos, and gorillas have each been evolving on their own unique evolutionary pathways while we hominids have taken different evolutionary trajectories. Ardipithecus connects us with the rest of life's tree in ways that living apes cannot. Living apes and modern genetics provide valuable windows on human evolution, but the Ardipithecus discoveries demonstrate the unique power of the fossil record to reveal the vanished worlds of our ancient African past.
To read the Science abstract, visit www.sciencemag.org/cgi/content/abstract/326/5949/64.
Bay Path College Chair of Science and Mathematics Gina Semprebon recently discussed her research in the Ardi study with 88.5 fm WFCR reporter Tina Antolini. The story aired on Thursday, October 22, during Morning Edition.
Listen to Dr. Semprebon's full interview by visiting the 88.5 fm WFCR Web site.
Science Cover -
Partial skeleton of Ardipithecus ramidus, a hominid species living about 4.4 million yearsago in Ethiopia. This female stood about 1.2 meters high. Eleven papers from an
international team of authors published in print and online in this special issue describe
the anatomy of this species and its habitat and discuss the implications for understanding human evolution. One result is that extant great apes are poor models for our last common ancestor with chimpanzees. [Image: © T. White, 2008]