April 11, 2013

Findings Confirm Early South African Hominins

Close examination of the lower jawbone, teeth and skeleton of the hominid species Australopithecus sediba proves conclusively that it is uniquely different from a closely related species, Australopithecus africanus, according to a series of papers authored by a scientific team that includes several Texas A&M University researchers.

Darryl de Ruiter, associate professor in the Department of Anthropology, is the lead author or co-author in a series of six papers detailing the findings in the current issue of Science magazine. Also included in the authorship are associate professor Thom Dewitt of the Department of Wildlife and Fisheries Sciences, as well as Keely Carlson, a current doctoral student, and Juliet Brophy, a recent doctoral graduate in the Department of Anthropology at Texas A&M.

In 2010 the team, comprised of researchers from the United States, Africa, Europe and Australia, discovered skeletal remains in a South African cave located about 30 miles from Johannesburg and dated to about 1.98 million years ago. The team named the new species Australopithecus sediba and showed that it displayed a mosaic of both human-like and ape-like characteristics shared with other forms of Australopithecus and modern-day humans.

However, some researchers contended the new skeletons belonged to a closely related species, Australopithecus africanus, and therefore did not represent a new species.

“We looked at the jawbone area and found definitive proof that the two are not the same species,” de Ruiter says of the findings.

“Australopithecus sediba is unique in size, shape and pattern of growth, though it does share features with older australopiths, as well as later specimens referred to Homo erectus. It represents a transitional form between australopiths and Homo, the genus to which we humans belong, though it looks more like Homo than any other australopith ever found.”

Australopiths belong to Australopithecus, a genus of hominins now extinct. Ape-like in structure and lifeways, yet walking bipedally similar to modern humans, they are believed to have played a significant role in human evolution, and it is generally held among anthropologists that some form of Australopithecus eventually evolved into Homo. They are just not sure which form of Australopithecus, which is why Australopithecus sediba, with its unique arrangement of Homo-like features, is so intriguing.

“We examined the remains and found several distinct individuals – possibly representing a family group. They all seemed to have died suddenly in the same event about 1.98 million years ago, but the remains are in surprisingly good shape.”

de Ruiter adds that the findings “show very strong support of Darwin’s theory of  evolution by natural selection.”

The team used a method called morphometrics that uses math and 3-D models to form a precise replica of the jawbones of species of Australopithecus and early Homo, but showing distinct differences in size and shape between them. In addition, they were able to demonstrate the growth trajectory from a juvenile to an adult form was unlike that of any other hominin species known, further supporting the unique appearance of Australopithecus sediba.

In 2012 several of these same researchers, including de Ruiter, proved that Australopithecus sediba had a forest-based diet of leaves, fruits, nuts and bark, one similar to that of a present-day chimp. The diet of early Australopithecus is a key component central to the study of human origins.

The team’s work was funded by the South African National Research Foundation, the Palaeontological Scientific Trust, the L.S.B. Leakey Foundation Baldwin Fellowship, the National Geographic Society, the Institute for Human Evolution at the University of Witwatersrand in Johannesburg, the Program to Enhance Scholarly and Creative Activities and the International Research Travel Assistance Grant of Texas A&M, and the Ray A. Rothrock ’77 Fellows Program in the College of Liberal Arts at Texas A&M.

###
About Research at Texas A&M University: As one of the world’s leading research institutions, Texas A&M is in the vanguard in making significant contributions to the storehouse of knowledge, including that of science and technology. Research conducted at Texas A&M represents an annual investment of more than $700 million. That research creates new knowledge that provides basic, fundamental and applied contributions resulting in many cases in economic benefits to the state, nation and world.

Media contact: Keith Randall, News & Information Services, at (979) 845-4644 or Darryl de Ruiter at (979) 845-5242

November 2, 2011

Prof Helping To Unravel Causes Of Ice Age Extinctions

Did climate change or humans cause the extinctions of the large-bodied Ice Age mammals (commonly called megafauna) such as the woolly rhinoceros and woolly mammoth? Scientists have for years debated the reasons behind the Ice Age mass extinctions, which caused the loss of a third of the large mammals in Eurasia and two thirds of the large mammals in North America, and now, an inter-disciplinary team from more than 40 universities around the world led by Professor Eske Willerslev and his group from the Centre for GeoGenetics, University of Copenhagen, have tried to answer the contentious question in one of the biggest studies of its kind ever.

The study by the team, which includes two Texas A&M University professors, is published online today in the journal Nature and reveals dramatically different responses of Ice Age species to climate change and human impact. Using ancient DNA, species distribution models and the human fossil record, the findings indicate that neither climate nor humans alone can account for the Ice Age mass extinctions.

“Our findings put a final end to the single-cause theories of these extinctions,” says Willserslev. “Our data suggest care should be taken in making generalizations regarding past and present species extinctions; the relative impacts of climate change and human encroachment on species extinctions really depend on which species we’re looking at.”

The study reports that climate alone caused extinctions of woolly rhinoceros and musk ox in Eurasia, but a combination of climate and humans played a part in the loss of bison in Siberia and wild horse. While the reindeer remain relatively unaffected by any of these factors, the reasons causes of the extinction of the mammoth remain unresolved.

The study also reports that climate change has been intrinsically linked with major population size changes over the past 50,000 years, supporting the view that populations of many species will decline in the future owing to climate change and habitat loss. Finally, the authors find no clear pattern in their data distinguishing species that went extinct from species that survived.

Eline Lorenzen, professor at the University of Copenhagen and lead author of the study, said, “The fact that we couldn’t pinpoint what patterns characterize extinct species — despite the large and varying amount of data analyzed — suggests that it will be challenging for experts to predict how existing mammals will respond to future global climate change. Which species will go extinct and which will survive?

“The bottom line is that we really don’t know why some of these ancient species became extinct,” adds Ted Goebel, researcher in the Department of Anthropology at Texas A&M and affiliated with the Center for the Study of First Americans.

“Now we can better predict what might happen to animals in the future as climate change occurs. What happens to species when their ranges are significantly diminished, and why do some animals adapt successfully while others become extinct?  We now have a genetic roadmap to follow in our efforts to protect sensitive animal populations – especially in drastically impacted regions like the Arctic.”

#####

About Research at Texas A&M University: As one of the world’s leading research institutions, Texas A&M is in the vanguard in making significant contributions to the storehouse of knowledge, including that of science and technology. Research conducted at Texas A&M represents an annual investment of more than $630 million, which ranks third nationally for universities without a medical school, and underwrites approximately 3,500 sponsored projects. That research creates new knowledge that provides basic, fundamental and applied contributions resulting in many cases in economic benefits to the state, nation and world.

Copenhagen Contacts: Prof. Director Eske Willerslev, Centre for GeoGenetics, University of Copenhagen. Øster Voldgade 5-7DK-1350, Denmark; Phone: +45 35321309/ +45 28751309; E-mail: ewillerslev@gmail.com, ewillerslev@snm.ku.dk, http://geogenetics.ku.dk/

Dr. Eline Lorenzen Centre for GeoGenetics, University of Copenhagen, Oester Voldgade 5-7 DK-1350; Denmark Office: +45 35 321225 Mobile: +45 26 701024; Email: elinelorenzen@gmail.com or edlorenzen@snm.ku.dk

Texas A&M Contact: Keith Randall, News & Information Services, at (979) 845-4644 or Ted Goebel, Department of Anthropology, (979) 862-4544

October 20, 2011

Texas A&M Study: Hunters Present At Least 800 Years Earlier Than Previously Thought

The tip of a bone point fragment found embedded in a mastodon rib from an archaeological site in Washington state shows that hunters were present in North America at least 800 years before Clovis, confirming that the first inhabitants arrived earlier to North America than previously thought, says a team of researchers led by a Texas A&M University archaeologist.

Michael Waters, director of the Center for the Study of the First Americans in the Department of Anthropology at Texas A&M, and colleagues from Colorado, Washington and Denmark believe the find at the Manis site in Washington demonstrates that humans were in the area around 13,800 years ago, or 800 years earlier than was believed. Their work is published in the current issue of Science magazine.

In the late 1970s, an adult male mastodon was excavated from a pond at the Manis site. The distribution of the bones and the discovery that some of the bones were broken suggested that the elephant had been killed and butchered by human hunters, Waters explains. However, no stone tools or weapons were found at the site. The key artifact from the site was what appeared to be a bone point sticking out of one of the ribs, but the artifact and the age of the site were disputed.

Waters contacted team member and original excavator, Carl Gustafson, about performing new tests on the rib with the bone point. New radiocarbon dates confirmed that the site was 13,800 years old. High resolution CT scanning and three-dimensional modeling confirmed that the embedded bone was a spear point, and DNA and bone protein analysis showed that the bone point was made of mastodon bone.

“The Manis site is an early kill site” Waters says.

“The evidence from the Manis site shows that people were hunting mastodons with bone weapons before the Clovis stone spear point.”

The new evidence from Manis supports extinction theories of large mammals at the end of the last Ice Age, Waters says. During the last cold period, herds of mammoth, mastodon, camels, horses and other animals roamed Texas and North America. At the end of the Ice Age, these animals became extinct.

“While these animals were stressed by the changing climate and vegetation patterns at the end of the Ice Age, it is now clear from sites like Manis that humans were also hunting these animals and may have been a factor in their demise,” Waters adds. He also notes that “there are at least two other pre-Clovis kill sites in Wisconsin where hunters killed mammoths.”

‘Clovis’ is the name given to the distinctive tools made by people starting around 13,000 years ago. The Clovis people invented the ‘Clovis point’, a spear-shaped weapon made of stone that is found in Texas and the rest of the United States and northern Mexico. These weapons were used to hunt animals, including mammoths and mastodons, from 13,000 to 12,700 years ago.

Waters says that “the evidence from the Manis site is helping to reshape our understanding of the earliest inhabitants of the Americas, the last continent to be occupied by modern humans.”

The study was funded by the North Star Archaeological Research Program at Texas A&M University.

#####

Media contact:  Keith Randall, News & Information Services, at (979) 845-4644 or Mike Waters at (979) 845-5246