, April 2010, by Edyta Zielinska  –  The question of how T cells escape the thymus and enter the circulation to fight infections has finally been answered.

“These findings will be taught in textbooks down the road,” Kristin Hogquist from the University of Minnesota, who was not involved in the research, wrote in an email. “This is a fascinating study,” she added.

Scientists have long wondered how T cells exit the thymus, where they mature. The thymus is threaded with both blood vessels and lymphatic vessels (containing lymphocytes suspended in a clear fluid), so researchers didn’t know which exit route T cells took.

New findings published this week in Science have settled the debate: Mature T cells escape the thymus via blood cells rather than lymphatic vessels.

Marcus Zachariah and Jason Cyster from the University of California in San Francisco investigated the question by looking at the receptor S1P1, expressed by mature T cells just before they exit the thymus. The receptor drives cells to areas, such as the blood, that are rich in S1P — the receptor’s ligand. However, it was recently shown that the S1P ligand in the blood wasn’t sufficient to draw T cells out of the thymus, Yousuke Takahama, from the University of Tokushima, who wasn’t involved in the research, said in an email.

The researchers observed T cells expressing the S1P1 receptor, and noticed that these cells accumulated at blood vessels of the thymus — specifically, near pericytes, a cell type that creates a sheath around blood vessels. This suggested that the S1P ligand on these pericytes was attracting the cells to that location.

When researchers deleted the S1P expression on pericytes only, T cells were unable to exit the thymus. “This study shows that S1P-mediated thymocyte egress is not a single-step process regulated by blood-borne S1P, but a multiple-step process,” regulated by both the S1P on the pericytes and in the blood, said Takahama.

M.A. Zacharia, J.G. Cyster, “Neural Crest-Derived Pericytes Promote Egress of Mature Thymocytes at the Corticomedullary Junction,” Science, published online April 22, 2010, doi:10.1126/science.1188222.

For Immediate Release:  April 26, 2010
Media Inquiries:  Dick Thompson, 301-796-7566;
Consumer Inquiries:  888-INFO-FDA

FDA Changes Process for Medical Device Advisory Committees
Goal is improved discussion and flow of information

The U.S. Food and Drug Administration today announced that it will change the way its expert panels review and discuss data and information during public hearings on medical devices under review for premarket approval, effective May 1, 2010.

The changes were prompted by an increasing number of medical device advisory panel meetings in recent years. In 2008, there were 10 panel meetings covering 14 major topics. In 2009, there were 17 meetings on 20 topics, and 2010 is on track to surpass those numbers, according to the FDA’s Center for Devices and Radiological Health (CDRH).

The increased activity has created challenges for CDRH and the way it operates panel meetings. In accord with current agency policy and guidance for advisory committees, the changes address staffing issues, voting procedures, and other items related to information presentation and flow of discussion.

“These changes are expected to empower the agency to make more effective decisions that are informed by more clear and focused discussion by panel experts,” said CDRH Director Jeffrey Shuren, M.D.

In the past, panel discussions have not always reflected a panel’s final vote on approvability. Now, instead of voting on the approvability of premarket approval applications, including conditions of approval, the panel will vote on the safety and effectiveness of a device and the device’s risk versus its benefit.

“By making this change in voting procedure, panel members will address key scientific issues during their discussions, which will be reflected in their votes,” Shuren said. “The change also will allow panel members to address issues related to their area of expertise instead of regulatory issues that may be unfamiliar to them.”

In addition, panels will vote by ballot instead of by a show of hands. While the votes will be publicly tallied so that panel members can be identified by their vote, the ballot process allows each panel member to cast his or her vote without immediate influence by other votes.

There are many issues involved in the FDA’s review of a medical device. Historically, the FDA’s presentations to panels included comments on approvability. With the changes, the FDA’s presentations will continue to include reviews of the agency’s data analysis, but will no longer include comments on approvability.

Before the changes, the agency medical device reviewers presented a unified, consensus analysis of supporting data. Now, reviewers will present together with data and analysis, the range of scientific opinion in the group. This move will allow more in-depth discussion on safety and effectiveness and risk versus benefit of the device under consideration..

The FDA and CDRH will continue to evaluate panel procedures and make changes when necessary. A detailed description of changes to panel operations can be found here1.

For more information:

Your Target Health Inc. Blogger is at the Experimental Biology Meeting in Anaheim, CA, by Kathleen Doheny, April 27, 2010 (Anaheim, California) — Eat more like a Greek, and less like a typical American, and you may be doing your brain a favor, new research suggests.

Older adults who adhere to the heart-healthy Mediterranean diet — rich in fruits, vegetables, olive oil, legumes, fish, and moderate amounts of wine — appear to have less mental decline with age, according to one of the latest studies on the health benefits of eating like a Greek.

”Those who adhered most closely to the Mediterranean diet performed as if they were two years  younger,” says study researcher Christy Tangney, PhD, a researcher at Rush University Medical Center, Chicago, who presented her findings Monday at EB 2010, the annual Experimental Biology meeting.

Exactly why the diet, already known for its heart-healthy effects, may protect brain function isn’t known, Tangney tells WebMD, but her research builds on other studies finding the diet preserves thinking and intellectual skills.

”I think there’s a strong cardiovascular component,” she says. Some of the diet components, such as the phytochemicals from fruits and vegetables, are thought to protect against neuron loss, she says.

Following the Mediterranean Diet

Tangney and her colleagues followed 3,790 men and women enrolled in the ongoing Chicago Health and Aging Project. The average age of the participants was 75, but all were over age 65. The follow-up averaged more than seven years.

The men and women answered a food-frequency questionnaire, spelling out in detail which components of the diet they ate and how often. The highest possible score for adherence to the Mediterranean diet is 55, but as Tangney notes, “No one followed it perfectly.”

Tangney then classified their adherence to the diet as low, medium, or high. Low followers scored 12 to 25, medium 26 to 29, and high 30 to 45.

The researchers administered several tests of mental function, such as short- and long-term recall, and compiled those scores as a ”global cognitive score.” The tests were given every three years.

Those in the top group knocked two years off their test scores, she says. For instance, if they were 65, they scored in the typical range for a 63-year-old.

There was some effect in the medium group, Tangney says, but no effect in the group that adhered the least.

The beauty of the finding, Tangney tells WebMD, is that following the diet perfectly isn’t necessary to get a brain-protective effect. “When someone incorporates a diet rich in fruits and vegetables and non-refined grains such as cereals and breads and breaks it up with a little wine, there appears to be at least some protection against cognitive aging,” she says.

While Tangney’s team didn’t inquire about exercise habits, she says physical activity would be ideal to add to the Greek-like diet. “The true Mediterranean diet advocates lots of physical activity,” she says.

Second Opinion

The study results ”are significant in that it tells us something may be going on” with the Greek-like diet and mental skills, says Bruce Semon, MD, PhD, a Milwaukee doctor who reviewed the study findings for WebMD.

”It’s a moderate effect,” he says of the two-year improvement found in the study.

Because the researchers looked at the diet as a whole, he says, it’s difficult to separate out which food or foods deserve credit for preserving brainpower.

Tangney says that’s a plus of the study. Many studies have focused on individual nutrients and their effect on health.

But her research looks at the ”big picture” of the Mediterranean diet and finds benefits for those who follow it closely, but not perfectly.

Her advice? ”Eat lots of whole grains, legumes, and beans. Have an occasional glass of wine.”


Christy Tangney, PhD, researcher, Rush University Medical Center, Chicago.

Bruce Semon, MD, PHD, researcher, Wisconsin Institute of Nutrition, Milwaukee.

EB 2010, Experimental Biology Meeting, Anaheim, Calif., April 24-28, 2010.

Sir Paul Nurse nominated as next President of the Royal Society

Paul Nurse PhD

Published Date: 23 April 2010

The Council of the Royal Society has agreed to nominate Nobel Laureate Sir Paul Nurse to be the new President of the Royal Society, it was announced today (23 April 2010).  

Following consultation with Fellows of the Royal Society, the Council of the Royal Society, selected Sir Paul as its nominated candidate to succeed Martin Rees.  Lord Rees completes his five-year term on 30 November 2010, the 350th Anniversary of the founding of the Society.

Fellows will be asked to indicate their support for the Council’s nominated candidate for President on the ballot paper for the annual election of Council members. The result of the ballot will be confirmed at the Council meeting on 8 July 2010.

Paul Nurse is a geneticist who works on what controls the division and shape of cells. He was Professor of Microbiology at the University of Oxford, CEO of the Imperial Cancer Research Fund and Cancer Research UK, and is presently President of Rockefeller University New York. He was awarded the Nobel Prize for Physiology or Medicine in 2001 and the Royal Society Copley Medal in 2005. He will be returning to the UK at the end of the year.

There have been 59 Presidents of the Royal Society since it was founded in 1660. Previous Presidents of the Royal Society have included Christopher Wren, Samuel Pepys, Isaac Newton, Joseph Banks, Humphry Davy, and Ernest Rutherford.

Cell transformation: A cocktail of three genes can transform skin cells into neurons (shown here in red).    Credit: Thomas Vierbuchen/Marius Wernig


New publications, experiments and breakthroughs in biomedicine–and what they mean


MIT Technology Review, May/June 2010, by Emily Singer  –  Better Cancer Tracking
Physicians could monitor cancer by screening for tumor DNA

Source: “Development of Personalized Tumor Biomarkers Using Massively Parallel Sequencing”
Victor Velculescu et al.
Science Translational Medicine
2: 20ra14

Results: Researchers from Johns Hopkins University analyzed the DNA of tumors in patients with breast and bowel cancer and found regions of abnormal, re­arranged DNA that served as unique biomarkers of each patient’s disease. They then measured levels of cancer-specific DNA in one patient before and after treatment. The ratio of cancer DNA to normal DNA in blood samples dropped dramatically after treatment, but the marker was still detectable, suggesting that the patient should be monitored more closely for possible recurrence of the disease.

Why it matters: Cancer arises when a number of genetic alterations in cells allow them to grow uncontrollably. Tracking those alterations in a patient’s cancer DNA could provide a new way of detecting small tumors or stray cancer cells that linger after treatment. Scientists say the DNA changes detected in the study will prove much more accurate than existing biomarkers such as the prostate-specific antigen (PSA) associated with prostate cancer, which may yield false positives because even healthy cells can produce the protein.

Methods: Researchers compared the genome sequence of patients’ healthy DNA and DNA isolated from tumor tissue. After isolating unique tumor signatures, they developed a test that uses DNA amplification to measure the amount of tumor DNA and normal DNA in blood.

Next steps: To determine how the technology can be most useful in medicine, researchers will use it to analyze different tumor types as well as different stages of tumor progression. They are also working on automating the technique and reducing its cost.

Replacement Neurons
A simple genetic ­recipe reveals the surprising flexibility of adult cells

Source: “Direct conversion of fibroblasts to functional neurons by defined factors”
Marius Wernig et al.
463: 1035-1041

Results: By making a few simple genetic tweaks, scientists can transform mouse skin cells directly into brain cells, without first returning them to the embryonic state required by previous methods. The resulting cells express neuron-specific genes, have the characteristic branching shape of neurons, and form connections both with each other and with regular neurons collected from the brain.

Why it matters: The research could someday offer an effective way to replace damaged neurons. Because brain cells derived from a skin graft would be genetically identical to the patient’s own tissue, they wouldn’t carry the risk of immune rejection associated with transplants. And scientists say the technique is faster than the existing approach to generating replacement brain cells from an individual patient: reprogramming adult cells to behave like embryonic cells and then prodding them to develop into neurons.

Methods: Scientists began by studying the genes for 19 transcription factors–proteins that bind to DNA and regulate expression of other genes. All were known to play a role in neural development and were found only in the brain. When the researchers used viruses to deliver two genes known to be particularly important for neural development into skin cells growing in a dish, they discovered that one of them had the power to convert the cells into what looked like immature neurons. They identified two additional genes that made the process faster and more consistent.

Next steps: The researchers are trying to repeat the process with human cells. They also plan to transplant the reprogrammed mouse cells into the brains of engineered mice that have a disease similar to Parkinson’s. Those experiments could reveal whether the cells can function properly in the brain and relieve symptoms of the disease.

Beat box: This implantable medical device bends and twists, thanks to transistors made of ultrathin ribbons of silicon. The electrode array shown here has 288 electrodes that can maintain contact with a heart even as it beats.   Credit: Science/AAAS


New flexible electronics can better chart the heart’s electrical activity


MIT Technology Review, by Duncan Graham-Rowe  –  A new flexible and biocompatible electronic device can produce a more detailed picture of the electrical activity of a beating heart. This high-resolution electrical map could help improve the diagnosis and treatment of heart abnormalities by pinpointing areas of damage or misfiring circuitry.

Today, the best way to map the electrical activity of a person’s heart is to insert a probe tipped with a few electrical sensors through a vein and into the heart. The probe is used to measure activity at different locations in the tissue to slowly build up a picture of electrical activity. An electrocardiogram, which picks up signals from outside the body, offers a less precise picture.

“It can take hours to map where these heart rhythms are coming from,” says Brian Litt, a neurologist and biomedical engineer at the University of Pennsylvania, and one of the senior researchers on the project. “If you map at a very high resolution, it may be possible that you can pick up, in local areas, precursors to arrhythmias before they occur.”

The flexible device can be used to attach multiple sensors to the wall of a beating heart, measuring electrical activity at multiple sites despite the heart’s movement. The electronics needed to record this activity are also built into the device, meaning more data can be collected. The new device is 25 microns thick and covers 1.5 square centimeters. It contains over 2,000 transistors sealed within a flexible coating and is covered with 288 sensor electrodes. So far the device has been tested successfully in pigs.

It is the first time that flexible electronics have been used in such high density in a medical device, says John Rogers, an engineer at the University of Illinois, Urbana-Champaign, who collaborated on the work. “These devices contain more transistors than any previously reported flexible device,” he says.

The flexible device could be used in other kinds of biological sensors, says Litt, including devices for monitoring neurological conditions such a Parkinson’s and epilepsy. The work, which also involved researchers from Northwestern University, is published in the journal Science Translational Medicine.

The key to making the device is what Rogers calls “nanomembrane transistors.” These components are made out thin ribbons of silicon, about 100 nanometers thick; on this scale the material loses its characteristic rigidity and becomes flexible. “It’s much like a piece of two-by-four,” Rogers says. “Wood is not very bendable, but a sheet of paper is.”

Making these transistors required a completely new fabrication technique. Rogers etched out the ribbon circuits from larger blocks of silicon and then used chemical etching to remove silicon from underneath. The circuits could then be peeled away when brought into contact with a stamp-like device.

Once the circuit has been deposited on a substrate, it is encased in a photocurable water-tight epoxy material. This material was difficult to develop, since it had to have the same mechanical properties as the circuit in order to bend with it, but also needed to be resilient enough to prevent any seepage, even at points where the electrodes protrude. “It probably took us half a year to develop a recipe for that,” says Rogers.

The next step, says Litt, is to build a power supply into the device so that it can be used for chronic implantation, and to find a way to transmit data from it wirelessly. The researchers are also developing a version that can also be used to ablate damaged heart tissue through localized heating.

“It is a very impressive advance for electrical mapping of the heart,” says Eric Topol, a cardiologist and director of the Scripps Translational Science Institution, in La Jolla, CA. Today the average ablation procedure for arterial fibrillation takes about three hours at best. “This jump in mapping capability could markedly reduce and simplify these procedures and many other interventions,” he says.

National Institute of Environmental Health Sciences (NIEHS)

For Immediate Release
April 2010


A report released today by a federal working group highlights 11 key categories of diseases and other health consequences that are occurring or will occur due to climate change. The report, A Human Health Perspective on Climate Change, provides a starting point for coordination of federal research to better understand climate’s impact on human health. The recommendations of the working group include research to identify who will be most vulnerable, and what efforts will be most beneficial.

“This white paper articulates, in a concrete way, that human beings are vulnerable in many ways to the health effects of climate change,” said Linda Birnbaum, Ph.D., director of the National Institute of Environmental Health Sciences (NIEHS) and the National Toxicology Program, whose institute led the interagency effort. “It lays out both what we know and what we need to know about these effects in a way that will allow the health research community to bring its collective knowledge to bear on solving these problems.”

The white paper highlights the state-of-the-science on the human health consequences of climate change on:

  • Asthma, respiratory allergies, and airway diseases
  • Mental health and stress-related disorders
  • Cancer
  • Neurological diseases and disorders
  • Cardiovascular disease and stroke
  • Waterborne diseases
  • Foodborne diseases and nutrition
  • Weather-related morbidity and mortality
  • Heat-related morbidity and mortality
  • Vectorborne and zoonotic diseases (like malaria, which can be transmitted from animals to humans)
  • Human developmental effects

The report also examines a number of cross-cutting issues for federal research in this area, including susceptible, vulnerable, and displaced populations; public health and health care infrastructure; capacities and skills needed; and communication and education efforts.

“Earth Day reminds us that changes in the environment are affecting our food, water, and our health,” said Birnbaum. “This report provides a guide for researchers throughout the world who are working to improve the health of the planet and the health of all people.”

“Increasingly, studies including some co-funded by NIEHS, recently published in The Lancet, have shown us that by understanding how climate change, human health, and human activities intersect,” said Howard Koh, M.D., assistant secretary for Health for HHS, “we can prevent some of climate’s worst impacts while providing huge benefits to human health that actually offset the costs of mitigation and adaptation. The white paper integrates these new data in a framework that is a new way of looking at this complex and critical problem.”

The ad hoc Interagency Working Group on Climate Change and Health was formed following a 2009 Institute of Medicine Roundtable on Environmental Health Sciences, Research, and Medicine meeting on climate change. At the gathering, leaders from NIEHS, the U.S. Environmental Protection Agency, the National Oceanographic and Atmospheric Administration, and the Centers for Disease Control and Prevention recognized that the scientific discussion around climate change needed to be reframed to emphasize the human health impacts and research needs to address them.

Led by Christopher Portier, Ph.D., from NIEHS, membership of the working group also includes representatives from the National Institutes of Health Fogarty International Center, the U.S. Department of Agriculture, the U.S. Department of State, the White House Office of Science and Technology Policy, and the U.S. Department of Health and Human Services, with support and input from the U.S. Global Change Research Program and others.

The report was released today online at (PDF – 5 MB), and in a special, supplemental issue of the journal Environmental Health Perspectives.

The NIEHS supports research to understand the effects of the environment on human health and is part of NIH. For more information on environmental health topics, visit our Web site at Subscribe to one or more of the NIEHS news lists ( to stay current on NIEHS news, press releases, grant opportunities, training, events, and publications.

The National Institutes of Health (NIH) — The Nation’s Medical Research Agency — includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit

Go here, to read the new health report from the NIH

Mary-Lou O’Neill, 73, has been helping Grace Jackson, 101, for four years. “It’s developed into a friendship,” Ms. Jackson said.

Published: April 25, 2010

The New York Times, PROVIDENCE, R.I. — One recent morning Antonia Antonaccio, a home care aide, got a call to help an elderly couple whose regular aide could not make it. The regular aide, who is 68 years old, had thrown out her back.

Ms. Antonaccio said she empathized. Sometimes her legs hurt from going up and down stairs. “But it’s nothing I pay attention to,” she said. “I don’t have the time.”

Ms. Antonaccio is 73.

In an aging population, the elderly are increasingly being taken care of by the elderly. Professional caregivers — almost all of them women — are one of the fastest-growing segments of the American work force, and also one of the grayest.

A recent study by PHI National, a nonprofit organization that advocates on behalf of caregivers, found that in 2008, 28 percent of home care aides were over age 55, compared with 18 percent of women in the overall work force.

The organization projects that from 2008 to 2018, the number of direct care workers, which includes those in nursing homes, will grow to 4.3 million from 3.2 million. The percentage of older caregivers is projected to grow to 30 percent from 22 percent.

The average caregiver in Rhode Island from Home Instead Senior Care, the private agency that employs Ms. Antonaccio, is about 60, said Valerie Topp, chief operating officer for the state franchise. Younger aides often do not work out, Ms. Topp said, adding that clients frequently ask that the agency not send over someone too young.

“The older ones came to us after being family caregivers, so they understood the stresses that families were under,” Ms. Topp said. “They came with respect for age. They didn’t see age as a disability.”

Carmine Spino, 89, and his wife, Mary, 88, who are hoping to live out their lives without moving to a nursing home, are two of Ms. Antonaccio’s clients. She often shares stories about growing up in Italy during World War II; Mr. Spino served in the war — a common ground. They know the same music, share the same cultural reference points.

And as Mrs. Spino, who was always quiet, has become more withdrawn with the onset of dementia, Mr. Spino relies on their caregivers for conversation.

“We talk about our experiences,” he said of Ms. Antonaccio. “I don’t look at her as a stranger.”

Caregivers often nurse their own aches and pains, or manage their medications, as they tend to those of their clients, said Dorie Seavey, director of policy research for PHI National. Clients who have to be lifted may not be suited to some older workers, she said.

Linnette Hutchinson, 71, of Tucson, said she often had the same complaints as her clients. “Your eyes are going, and the aches and pains,” she said. “Your back, your legs, your teeth. The aging process sets in.” Ms. Hutchinson has had spinal surgery but still works four hours a day.

For Mara Torres-Rullan, 74, also of Tucson, the big challenge is pain. She started work as a caregiver in 1987 after a divorce; in recent years she has cut her hours because of arthritis.

“My last lady, I had to put pantyhose on her,” Ms. Torres-Rullan said. “I thought my back was going to break in half.”

She continues to work because she needs the money, but she refuses any clients who want vacuuming done because the work is too painful.

In Plymouth, Mass., Judy Brueggeman, 68, felt increasingly fatigued last year and had a stress test on her heart. “After three to five seconds on the treadmill, the doctor shut it off and told me to lie down and be quiet,” she said. She had triple bypass surgery in September.

But even so, she is now back on the job, putting in 12-hour weeks. “This is perfect for me,” she said. “I love my clients, and I love my work.” In some ways, Ms. Brueggeman said, the work has gotten easier because she is better at it than when she started, in 1991. “I learned a lot from my clients, especially not to talk too much,” she said. “They want to do the talking.”

But the industry does not have career paths for workers as they get older, putting a strain on them to continue with the most physically demanding aspects of the job, Ms. Seavey said. “If you look at older women as an asset, to train younger workers, they can be valuable,” she said. Ms. Antonaccio worked in the jewelry industry for 40 years before retiring, then went to work as a caregiver after her husband’s death, drawn by the flexible hours. She did not need health benefits because she was eligible for Medicare. She did need a sense of purpose.

“At 65, I felt my life was ending,” she said. “I took care of my mother, then my mother-in-law, then my husband, then I went into this. And I don’t have any intention to stop.”

Home Instead pays her roughly half the $19.25 an hour it charges clients in Rhode Island.

Her age, she said, makes her more sympathetic to the needs of her clients.

“They need someone to understand them,” she said. “When I first came, Carmine was in the hospital” — Mr. Spino was having respiratory problems — “and Mary was scared. She didn’t understand what was going on. She woke up and her husband wasn’t there. She wanted to call him every five minutes. I had to say he needs his sleep.”

Grace Jackson, who is 101, said she never wanted a helper at home and resented Mary-Lou O’Neill, 73, when she arrived four years ago at Ms. Jackson’s daughters’ insistence. But as their relationship has grown, “It’s developed into a friendship,” Ms. Jackson said, adding that friends who had younger aides were often offended by their manners or language.

Ms. O’Neill worked as a nurse until she was 66, then found herself restless in retirement. Now, she is one of the large number of Americans in their 70s who are still active and robust, without physical pain or limitations. She works only for Ms. Jackson.

“She’s a role model to me,” Ms. O’Neill said. “When she has physical problems, she doesn’t complain.”

Ms. Jackson said she appreciated having a companion with a wealth of life experiences. Last spring, after hip surgery, she complained in the rehabilitation center that she wanted to die.

“‘O.K.,” Ms. O’Neill told her, “if you want to die, get better and die at home.”

Ms. Jackson got better. From a younger aide, Ms. Jackson said, she would not have accepted such a challenge.

“Not that I don’t get along well with younger people,” she said. “But I’m not always pleased, I don’t like the way they talk. Maybe that’s what keeps you alive — not accepting everything.”

Target Health predicted this long ago……now here’s the science to prove it…………….

Genetic data points to ancient liaisons between species.,, April 26, 2010, by Rex Dalton  –  Archaic humans such as Neanderthals may be gone but they’re not forgotten — at least not in the human genome. A genetic analysis of nearly 2,000 people from around the world indicates that such extinct species interbred with the ancestors of modern humans twice, leaving their genes within the DNA of people today.

The discovery, presented at the annual meeting of the American Association of Physical Anthropologists in Albuquerque, New Mexico, on 17 April, adds important new details to the evolutionary history of the human species. And it may help explain the fate of the Neanderthals, who vanished from the fossil record about 30,000 years ago. “It means Neanderthals didn’t completely disappear,” says Jeffrey Long, a genetic anthropologist at the University of New Mexico, whose group conducted the analysis. There is a little bit of Neanderthal leftover in almost all humans, he says.

The researchers arrived at that conclusion by studying genetic data from 1,983 individuals from 99 populations in Africa, Europe, Asia, Oceania and the Americas. Sarah Joyce, a doctoral student working with Long, analyzed 614 microsatellite positions, which are sections of the genome that can be used like fingerprints. She then created an evolutionary tree to explain the observed genetic variation in microsatellites. The best way to explain that variation was if there were two periods of interbreeding between humans and an archaic species, such as Homo neanderthalensis or H. heidelbergensis.

“This is not what we expected to find,” says Long.

Using projected rates of genetic mutation and data from the fossil record, the researchers suggest that the interbreeding happened about 60,000 years ago in the eastern Mediterranean and, more recently, about 45,000 years ago in eastern Asia. Those two events happened after the first H. sapiens had migrated out of Africa, says Long. His group didn’t find evidence of interbreeding in the genomes of the modern African people included in the study.

The researchers suggest that the population from the first interbreeding went on to migrate to Europe, Asia and North America. Then the second interbreeding with an archaic population in eastern Asia further altered the genetic makeup of people in Oceania.

The talk at the anthropology meeting caught the attention of many researchers, some of whom have been trying to explain puzzling variations in the human genome. “They are onto something,” says Noah Rosenberg, an anthropological geneticist at the University of Michigan in Ann Arbor, who heard the talk.

A test of the New Mexico team’s proposals may come soon. Svante Pääbo and colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, announced early last year that they had finished sequencing a first draft of the Neanderthal genome, and they are expected to publish their work in the near future. Pääbo’s earlier studies on components of Neanderthal genomes largely ruled out interbreeding, but they were not based on more comprehensive analyses of the complete genome.

Linda Vigilant, an anthropologist at the Planck Institute, found Joyce’s talk a convincing answer to “subtle deviations” noticed in genetic variation in the Pacific region.

“This information is really helpful,” says Vigilant. “And it’s cool.”

The paleontological record also is producing fossils that complement such interbreeding theories. Pääbo’s team and Russian colleagues recently reported the mitochondrial genome of an archaic human from the Altai Mountains — in southern Siberia near ancient Asian trade routes1.

The ancient mitochondrial DNA came from a piece of finger bone, which the groups haven’t identified by species. It could be Neanderthal, a new Homo species or some other archaic form — like H. erectus, who spread to Oceania by 1.8 million years ago.

The Pääbo team reported that the bone was from an individual that lived 30,000–48,000 years ago in Denisova Cave, near where both modern humans and Neanderthals then dwelled. But the age of the bone has been questioned by researchers, who say the cave’s sediments may have been reworked, making the

bone’s layer older.  At the anthropology meeting, Theodore Schurr, a molecular anthropologist at the University of Pennsylvania in Philadelphia, said the genetic model showing interbreeding raises questions about the range of species, like H. heidelbergensis. He noted that human skeletons found at Lake Mungo in New South Wales, Australia, have robust features, which may represent the result of interbreeding; they are dated to more than 20,000 years ago.

Keith Hunley, another member of the New Mexico group, said the team is now moving to publish its results in the near future. 

·                                 References

  1. Krause, J. et al. Nature doi:10.1038/nature08976 (2010).

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