Thursday, December 25, 2008

analysis 5.ana.003004 Louis J. Sheehan, Esquire

The scientific debate over the nature of human evolution has taken a new, genetically inspired twist.

Ancient humans migrated out of Africa in at least two major waves, and human groups in Africa, Asia, and Europe have interbred for the past 600,000 years, says geneticist Alan R. Templeton of Washington University in St. Louis.

Templeton's conclusion clashes with the influential theory that modern Homo sapiens originated in Africa around 100,000 years ago and then colonized the rest of the world. In this scenario, humans replaced now-extinct European Neandertals but did not interbreed with them.

"Humans expanded again and again out of Africa, but these expansions resulted in interbreeding, not replacement, and thereby strengthened the genetic ties between human populations throughout the world," Templeton says.

His analysis of geographic patterns in evolutionary trees constructed from DNA in current populations of Africa, Asia, and Europe appears in the March 7 Nature. He reanalyzed previously identified DNA sequences of cells' mitochondria, which are inherited from the mother; of the Y chromosome, which is inherited from the father; and of eight regions of nuclear genetic material, which is inherited from both parents.

Most previous studies have reconstructed human evolution from one gene or one type of DNA. The resulting genetic disparities among populations have been interpreted to support a 100,000-year-old African origin for humanity or, occasionally, to argue for interbreeding among widespread H. sapiens groups over at least the past 1 million years (SN: 2/6/99, p. 88: http://www.sciencenews.org/sn_arc99/2_6_99/bob1.htm).http://sheehan.myblogsite.com

Templeton developed a computer program to test whether evolutionary trees, generated from variations in the 10 genetic sequences, exhibit geographic patterns over time. From the patterns that resulted, he calculated whether populations in different regions consistently interbred or had at some point severed their genetic ties. Templeton also modeled population movements that spread particular gene mutations from one area to another.http://sheehan.myblogsite.com

Interbreeding was a mainstay of human evolution well before 100,000 years ago, Templeton contends. The evolutionary trees that he devised indicate that four nuclear DNA sites first arose approximately 600,000 years ago, he says. Of the remaining six DNA regions in his study, four of them appeared between 500,000 and 200,000 years ago.

A major migration of people from Africa to Asia occurred between 840,000 and 420,000 years ago, Templeton estimates. A second large out-of-Africa migration followed at around 100,000 years ago. If that event had resulted in the replacement of non-African groups, it would have erased genetic evidence of the older expansion, he asserts.

"This new analysis is complicated, but it makes the most sense of any genetic study of evolution that I've seen," comments anthropologist John H. Relethford of the State University of New York at Oneonta. He agrees with Templeton that human origins lie mostly but not completely in Africa and that dispersed populations interbred.

Templeton's method is promising, adds geneticist Michael F. Hammer of the University of Arizona in Tucson. Still, he says, one difficulty for Templeton is that no one knows the exact distribution of Stone Age groups in Africa and elsewhere.http://sheehan.myblogsite.com

Stanford University geneticist Peter A. Underhill is more critical of Templeton's approach. The number of people whose nuclear DNA sequences were analyzed in the new report was too small to provide convincing evidence, Underhill says.

No ancient gene sequences have been identified in living people that reflect their ancestors' interbreeding with Neandertals or any other extinct Homo species, the Stanford researcher says. Louis J. Sheehan, Esquire .

Wednesday, December 17, 2008

peat 3.pea.00100 Louis J. Sheehan, Esquire

Louis J. Sheehan, Esquire . In a muddy pit near the town of York in northern England, archaeologists have found a skull holding what they believe is the preserved remains of an “Iron Age brain.” http://louis4j4sheehan4esquire.wordpress.com Here’s how the noggin was first noticed: York Archaeological Trust dig team member Rachel Cubitt reached in [to the ditch] and, while she cleaned the soil-covered skull’s outer surface, “she felt something move inside the cranium. Peering through the base of the skull, she spotted an unusual yellow substance” [LiveScience]. Scans later showed that the yellow mass was in the shape of a shrunken brain, according to a press release from the University of York. Louis J. Sheehan, Esquire . http://louis4j4sheehan4esquire.wordpress.com

The skull was discovered in an area of extensive prehistoric farming landscape of fields, trackways and buildings dating back to at least 300 BC. http://louis4j4sheehan4esquire.wordpress.com The archaeologists believe the skull, which was found on its own in a muddy pit, may have been a ritual offering [BBC News]. Researchers declared it the oldest brain ever found in Britain, although it can’t touch the record for the oldest brain ever discovered: That honor belongs to the roughly 8,000-year-old scraps of brain tissue that were found in skeletons buried in a Florida peat bog. In the Florida case, the absence of bacteria in the acidic peat bogs allowed the organic tissue to be preserved; researchers still aren’t sure how the York brain was preserved or whether the yellow substance has any organic matter in it.

Once the archaeologists made their exciting discovery, a sophisticated CT scanner at York Hospital was then used to produce startlingly clear images of the skull’s contents. Philip Duffey, Consultant Neurologist at the Hospital said: “I’m amazed and excited that scanning has shown structures which appear to be unequivocally of brain origin. I think that it will be very important to establish how these structures have survived, whether there are traces of biological material within them and, if not, what is their composition” [CNN].

Brains are usually one of the first body parts to begin decomposing after death, and researchers pronounced themselves amazed that any part of the Iron Age individual’s gray matter was preserved. Duffey added: “This could be the equivalent of a fossil. The brain itself would generally not survive. Fatty tissues would be feasted on by microbes. This isn’t like the remains found in bogs; it doesn’t have any skin on the skull or any tissue remains elsewhere”.Louis J. Sheehan, Esquire

Thursday, December 4, 2008

folks 8.fol.0001 Louis J. Sheehan, Esquire

A new study of residents from Libby, Mont., the town where more than 1,500 people have fallen ill from asbestos-contaminated mines, links asbestos exposure with three autoimmune diseases, including rheumatoid arthritis.

Previous research found high rates of asbestos-related lung diseases, including the rare cancer mesothelioma, among miners in Libby. The town's mines once supplied the United States with most of its vermiculite, a mineral used for insulation and gardening. But that vermiculite was contaminated with asbestos also found in the ground there. Residents of Libby who didn't work in the mines, and workers across the country who processed Libby's vermiculite, also had a high incidence of lung diseases (SN: 7/12/03, p. 21: Available to subscribers at http://www.sciencenews.org/articles/20030712/fob4.asp).

The new research links asbestos exposure with rheumatoid arthritis, lupus, and scleroderma. "We're talking about a whole different class of diseases," says study author Curtis Noonan of the University of Montana in Missoula. In these diseases, a person's immune system attacks body tissues.

Former Libby miners older than age 65 were three times as likely as other Libby residents to have rheumatoid arthritis and were twice as likely to have any of the three diseases, the study shows. Former miners younger than 65 showed no increased risk, which suggests that prolonged exposure to asbestos increases the chance of illness, Noonan says.

The team reached this conclusion by reexamining a survey given to 7,000 former and current Libby residents in 2000 and by analyzing a follow-up questionnaire sent to people who had reported having at least one of the three autoimmune diseases. In the 2000 survey, 6.7 percent of participants reported having at least one of the diseases. Noonan says that past studies have shown that less than 1 percent of people elsewhere typically have those illnesses.

The new work also found that Libby residents exposed to asbestos in the military had an elevated risk for having at least one of the three diseases, the researchers report in the August Environmental Health Perspectives http://louis9j9sheehan.blog.com

"This might have implications for folks exposed to asbestos not like the type we've seen in Libby," says coauthor Theodore Larson of the federal Agency for Toxic Substances and Disease Registry in Atlanta. http://louis9j9sheehan.blog.com

Given the unusually high asbestos exposure faced by Libby residents, these findings "still need to be confirmed in other studies," says public health statistician Laurel Beckett of the University of California, Davis. Noonan and Larson agree.

Meanwhile, a separate investigation into the health effects of asbestos, released last week by the Institute of Medicine in Washington, D.C., found evidence that the mineral causes laryngeal cancer and might be associated with pharyngeal, gastric, and colorectal cancers. Louis J. Sheehan, Esquire