CU News
News from the University of Colorado in Boulder.
Asian migrants stuck on land bridge for milleniums
Feb 27th
likely a long-term refuge for early Americans
A new study led by the University of Colorado Boulder bolsters the theory that the first Americans, who are believed to have come over from northeast Asia during the last ice age, may have been isolated on the Bering Land Bridge for thousands of years before spreading throughout the Americas.
The theory, now known as the “Beringia Standstill,” was first proposed in 1997 by two Latin American geneticists and refined in 2007 by a team led by the University of Tartu in Estonia that sampled mitrochondrial DNA from more than 600 Native Americans. The researchers found that mutations in the DNA indicated a group of their direct ancestors from Siberia was likely isolated for at least several thousand years in the region of the Bering Land Bridge, the now-submerged plain that lies between northeast Asia and Alaska once exposed by a significantly lower sea level.
CU-Boulder researcher John Hoffecker, lead author of a short paper article appearing in the Feb. 28 issue of Science magazine, said the Beringia Standstill model gained little traction outside of the genetics community after it was proposed and has been seen by some scientists outside of the field as far-fetched. But the new paper by Hoffecker and co-authors Scott Elias of Royal Holloway, University of London, and Dennis O’Rourke of the University of Utah adds credence to the Beringia Standstill idea by further linking the genetics to the paleoecological evidence.
“A number of supporting pieces have fallen in place during the last decade, including new evidence that central Beringia supported a shrub tundra region with some trees during the last glacial maximum and was characterized by surprisingly mild temperatures, given the high latitude,” said Hoffecker of CU-Boulder’s Institute of Arctic and Alpine Research. The last glacial maximum peaked roughly 21,000 years ago and was marked by the growth of vast ice sheets in North America and Europe.
While a debate rages on about when early humans first migrated into the New World, many archaeologists now believe it was sometime around 15,000 years ago after retreating glaciers opened access to coastal and interior routes into North America.
The relatively mild summer climate in Beringia at the time was caused by North Pacific circulation patterns that brought moist and relatively warm air to the region during the last glacial maximum. Geologists believe the Beringia gateway between Siberia and Alaska was more than 600 miles wide at the time.
Hoffecker and others are now theorizing that a population of hundreds or thousands of people parked itself in central Beringia for 5,000 years or more. One key to the extended occupation may have been the presence of wood in some places to use as a fuel to supplement bone, which burns hot and fast. Experiments have shown that at least some wood is necessary to make bone practical as a fuel.
Elias, a paleoecologist and also an INSTAAR affiliate, said research using fossil pollen, plant and insect material from sediment cores from the now submerged landscape show that the Bering Land Bridge tundra environment contained enough woody plants and trees like birch, willow and alder to provide a supplement to bone.
Work by Elias and others included the analysis of certain beetle species that live in very specific temperature zones, allowing them to be used as tiny thermometers. The insects indicated that temperatures there were relatively mild during last glacial maximum that ran from about 27,000 years to 20,000 years ago, only slightly cooler than temperatures in the region today.
“The climate on the land bridge and adjacent parts of Siberia and Alaska was a bit wetter than the interior regions like central Alaska and the Yukon, but not a lot warmer,” said Elias. “Our data show that woody shrubs were available on the land bridge, which would have facilitated the making of fires by the people there.”
Evidence from the 2007 study indicated a set of genetic mutations in mitochondrial DNA, which is passed down from mother to offspring, clearly accumulated after the divergence of people from their Asian parent groups in Siberia but before their dispersal throughout the Western Hemisphere, said O’Rourke. In addition, ancient DNA from human skeletal remains found at a 24,000-year-old archaeological site in southern Siberia also appears consistent with the divergence of Native American groups from their Asian forbearers by that time window, he said.
“The genetic record has been very clear for several years that the Native American genome must have arisen in an isolated population at least by 25,000 years ago, and the bulk of the migrants to the Americas really didn’t arrive south of the ice sheets until nearly 15,000 years ago,” O’Rourke said. “The paleoecological data, which I think most geneticists have not been familiar with, indicate that Beringia was not a uniform environment, and there was a shrub tundra region, or refugium, that likely provided habitats conducive to continuous human habitation.”
“From my view the genetics and paleoecology data come together nicely,” said Hoffecker, who co-authored a 2007 book with Elias titled “The Human Ecology of Beringia.” While the weakest link to the Out of Beringia theory is the lack of archaeological evidence, Hoffecker believes future research on now submerged parts of Beringia as well as lowlands in western Alaska and eastern Siberia that still remain above water may hold clues to ancient habitation by Beringia residents, who eventually moved on to be the first group to inhabit the Americas.
Hoffecker also believes that the Beringia inhabitants during the last glacial maximum could have made successful hunting forays into the uninhabited steppe-tundra region to both the east and west, where drier conditions and more grass supported a plentiful array of large grazing animals, including steppe bison, horse and mammoth.
There is now solid evidence for humans in Beringia before the last glacial maximum, as geneticists first predicted in 1997, said Hoffecker. After the maximum, there are two sets of archaeological remains dating to less than 15,000 years ago. “One represents a late migration from Asia into Alaska at that time,” he said. “The other has no obvious source outside Beringia and may represent the people who are thought to have sheltered on the land bridge during the glacial maximum.
“If we are looking for a place to put all of these people during the last glacial maximum, Beringia may be the only realistic option,” said Hoffecker.
A video news story on the research is available at http://www.colorado.edu/news.
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CU: Shakespeare on the road in anti-violence drive
Feb 25th
third anti-violence school tour
Following on the heels of its nationally recognized anti-violence school tours based on “The Tempest” and “Twelfth Night,” the Colorado Shakespeare Festival has hit the road with a new production of “Much Ado About Nothing.”
The highly praised program, co-created with the Center for the Study and Prevention of Violence at the University of Colorado Boulder, brings abridged productions of Shakespeare’s plays into schools to stimulate discussion about the “cycle of violence.” More than 38,000 Colorado schoolchildren have participated in the program, which was launched in 2011.
Professional actors perform the play and lead students in small-group exercises exploring issues raised, such as gossip and bullying. Actors receive training through the Center for the Study and Prevention of Violence and, among other things, educate students about Safe2Tell, an anonymous tip line to report bullying.
The new production focuses on the potential damage caused by gossip and the power of language, said Amanda Giguere, director of outreach for the festival.
In the play, Beatrice and Benedick are “frenemies” known for their constant verbal sparring. Their friends play a prank on them by gossiping within earshot about their mutual affection. In the meantime, the villain Don John fabricates a nasty rumor about Hero’s infidelity, which results in her public humiliation on her wedding day.
“Gossip and rumors can quickly damage a reputation and can have a negative impact on a person’s self-esteem,” Giguere said. “This play explores the power of words. When does a ‘merry war’ turn hostile? When does teasing go too far? What kind of damage can rumors cause? It’s a perfect vehicle for engaging students with questions about the cycle of violence and the negative impact gossip can have on a school climate.”
Some 26 percent of high school students report that other students have told lies or spread rumors about them, according to Beverly Kingston, director of the Center for the Study and Prevention of Violence.
“Every day, kids are faced with difficult issues like gossiping and spreading rumors,” she said. “This play brings these issues to life and empowers students to reflect on these topics and see how they can make better choices.”
Whether they are exploring rumor-mongering, bullying or other harmful behaviors, one key goal of the plays and workshops is to help students feel empowered.
“One of the best things schools can do is to promote a positive school climate where students feel physically and emotionally safe,” Kingston said. “School climate is continuously created in every single interaction. This play is a tangible action toward building a positive school climate.”
Colorado Shakespeare Festival’s anti-violence production of “Much Ado About Nothing” is available for booking. For more information email csfedout@colorado.edu, call 303-492-1973 or visit coloradoshakes.org/education/csf-schools.
The Colorado Shakespeare Festival is a professional theater company in association with CU-Boulder and has performed the works of Shakespeare every summer since 1958. The Center for the Study and Prevention of Violence is part of CU-Boulder’s Institute of Behavioral Science. The anti-violence school tour is funded in part through grants from CU Outreach, the Boulder Arts Commission, the OAK (Outstanding Acts of Kindness) Foundation and One Lafayette.
The current tour began Feb. 11 and remaining tour dates include:
Feb. 25: St. Bernadette Catholic School and Mountain Phoenix Community School (Lakewood/Wheat Ridge)
Feb. 26: OLLI West and Denver Montclair International (Denver)
Feb. 27: Heatherwood Elementary (Gunbarrel)
Feb. 28: Brady High (Lakewood) and Jefferson Academy Elementary (Broomfield)
March 4: Ouray School
March 5: Ridgway Schools
March 7: Cherokee Trail High (Aurora) and CU-Boulder
March 14: Boulder Country Day
March 18: Endeavor Academy (Centennial)
March 20: Lincoln Academy Charter (Arvada)
March 21: McGlone Elementary (Denver)
April 1: Estes Park Schools
April 2: Louisville Middle School
April 3: Stein Elementary (Lakewood)
April 4: Estes Park Schools
April 8: Colfax Elementary (Denver) and East Elementary (Littleton)
April 9: Niwot Elementary
April 10: Bromwell Elementary and Columbian Elementary (Denver)
April 11: Rocky Mountain Elementary (Longmont) and Longmont Estates Elementary (Longmont)
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CU: Stem cells boost aging muscles
Feb 16th
to new methods of mitigating muscle loss
New findings on why skeletal muscle stem cells stop dividing and renewing muscle mass during aging points up a unique therapeutic opportunity for managing muscle-wasting conditions in humans, says a new University of Colorado Boulder study.
According to CU-Boulder Professor Bradley Olwin, the loss of skeletal muscle mass and function as we age can lead to sarcopenia, a debilitating muscle-wasting condition that generally hits the elderly hardest. The new study indicates that altering two particular cell-signaling pathways independently in aged mice enhances muscle stem cell renewal and improves muscle regeneration.
One cell-signaling pathway the team identified, known as p38 MAPK, appears to be a major player in making or breaking the skeletal muscle stem cell, or satellite cell, renewal process in adult mice, said Olwin of the molecular, cellular and developmental biology department. Hyperactivation of the p38 MAPK cell-signaling pathway inhibits the renewal of muscle stem cells in aged mice, perhaps because of cellular stress and inflammatory responses acquired during the aging process.
The researchers knew that obliterating the p38 MAPK pathway in the stem cells of adult mice would block the renewal of satellite cells, said Olwin. But when the team only partially shut down the activity in the cell-signaling pathway by using a specific chemical inhibitor, the adult satellite cells showed significant renewal, he said. “We showed that the level of signaling from this cellular pathway is very important to the renewal of the satellite cells in adult mice, which was a very big surprise,” said Olwin.
A paper on the subject appeared online Feb. 16 in the journal Nature Medicine.
One reason the CU-Boulder study is important is that the results could lead to the use of low-dose inhibitors, perhaps anti-inflammatory compounds, to calm the activity in the p38 MAPK cell-signaling pathway in human muscle stem cells, said Olwin.
The CU-Boulder research team also identified a second cell-signaling pathway affecting skeletal muscle renewal – a receptor known as the fibroblast growth factor receptor-1, or FGFR-1. The researchers showed when the FGFR-1 receptor protein was turned on in specially bred lab mice, the renewal of satellite cells increased significantly. “We still don’t understand how that particular mechanism works,” he said.
Another major finding of the study was that while satellite cells transplanted from young mice to other young mice showed significant renewal for up to two years, those transplanted from old mice to young mice failed. “We found definitively that satellite cells from an aged mouse are not able to maintain the ability to replenish themselves,” Olwin said. “This is likely one of the contributors to loss of muscle mass during the aging process of humans.”
Co-authors included first author and CU-Boulder postdoctoral researcher Jennifer Bernet, former CU-Boulder graduate student John K. Hall, CU-Boulder undergraduate Thomas Carter, and CU-Boulder postdoctoral researchers Jason Doles and Kathleen Kelly-Tanaka. The National Institutes of Health and the Ellison Medical Foundation funded the study.
Olwin said skeletal muscle function and mass decline with age in humans beginning at roughly age 40. While there are a variety of muscle-wasting diseases — ranging from muscular dystrophy to Lou Gehrig’s disease — the condition known as sarcopenia can lead to severe muscle loss, frailty and eventual death and is leading to skyrocketing health care costs for the elderly. “If you live long enough, you’ll get it,” he said.
Olwin and his team worked closely on the research with a team from Stanford University led by Professor Helen Blau, which published a companion paper in the same issue of Nature Medicine. “We shared data with the Stanford team during the entire process and we all were very pleased with the study outcomes,” said Olwin. “This is how science should work.”