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Three British men who suffered left brain damage that undermined their capacity to speak and understand language still possess a firm grasp of mathematics, a new study finds. This observation dramatically illustrates the presence of separate brain systems for language and numbers, at least in adults, say neuroscientist Rosemary A. Varley of the University of Sheffield in England and her coworkers.

The findings, however, are unlikely to resolve a long-running debate over whether children use language to develop their number sense. Some researchers argue that initial math insights arise from knowledge of the words for numbers or of grammatical rules for arranging words in phrases. Other scientists suspect that, from infancy on, language and math follow different mental and neural paths.

"I believe that dedicated brain mechanisms exist [from the start] for language and mathematics, but others on my team disagree with me," Varley says.

An account of the new investigation will appear in the March 1 Proceedings of the National Academy of Sciences.

The men who participated ranged in age from 56 to 59. Burst or injured blood vessels had damaged left brain tissue at least 3 years before the researchers tested the men's skills.

Participants exhibited little facility with language and were especially poor at grammar. They spoke only in single words and sentence fragments. Moreover, they couldn't distinguish the meanings of simple sentences with subject and object reversed, such as "The lion killed the man" and "The man killed the lion."http://ljsheehan.livejournal.com

Yet each participant readily solved mathematical problems, including those that require applying number-combination rules that the researchers view as analogous to grammatical rules for combining words and phrases. For example, the men successfully calculated answers to equations with reversed terms, such as 59-13 and 13-59. They also solved problems such as 36/(3 x 2), which have a structure similar to a sentence with dependent clauses.

The new study "provides additional evidence that mathematics and language are functionally and neuroanatomically independent," remarks neuroscientist Elizabeth M. Brannon of Duke University in Durham, N.C., in an editorial to be published with the study.

Such research, Brannon notes, can't exclude the possibility that the evolution of grammar in language provided a basis for mathematical rules or that children use early language discoveries as a foundation for learning about math.

Knowledge of mathematical rules by infants or nonhuman animals has yet to be demonstrated.

Investigators of two Brazilian cultures that lack words for numbers greater than 5 have concluded that language is necessary for people to conceive of and manipulate numbers. In tests, members of both cultures could identify large quantities that had been formed from two smaller quantities, say, 30 and 20, even though they couldn't name them. But precise arithmetic problems stumped these people.Louis J. Sheehan

Those findings don't necessarily show that language is necessary for mathematical thinking, contend two researchers in the January Trends in Cognitive Sciences. Rochel Gelman of Rutgers University in Piscataway, N.J., and Brian Butterworth of University College London say that people who don't need more than a handful of discrete numbers in their everyday lives may still be using a rudimentary, language-independent counting system.

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Despite sharing much of their genetic identity with people, chimpanzees exhibit previously unappreciated DNA distinctions, according to the first rigorous comparisons of the two species' complete genetic sequences. http://www.soulcast.com/Louis_J_Sheehan_Esquire_1

The new research "dramatically narrows the search for the key biological differences between the species," says geneticist Robert Waterston of the University of Washington School of Medicine in Seattle.

Waterston led an international consortium that analyzed the genetic sequence of a male common chimp and compared it with DNA data from people (SN: 4/19/03, p. 245: Available to subscribers at http://www.sciencenews.org/articles/20030419/fob6.asp). Initial results from their study, and from four related studies, appear in the Sept. 16 Science and the Sept. 1 Nature.

Waterston's group found that the roughly 3 billion base pairs in the genomes of the two species have the same sequence 96 percent of the time. Even so, as many as 3 million base pairs, or DNA building blocks, residing within protein-encoding and other functional areas of the genome differ between chimps and humans.

The new cross-species comparison identified six DNA segments in people that appear to have been strongly shaped by natural selection over just the past 250,000 years. Gene functions in these regions are largely unknown.

Differences in the evolutionary duplication of complete or partial genes, not of individual base pairs, primarily distinguish chimp DNA from that of people, report Washington's Evan E. Eichler and his coworkers. Differing degrees of gene duplications account for 2.7 percent of chimp and human DNA, whereas single base pair differences represent 1.2 percent. http://www.soulcast.com/Louis_J_Sheehan_Esquire_1

In both chimps and people, the tip regions of chromosomes appear most volatile, showing signs of frequent gene duplication and migration of various genes from one location to another, according to a group led by Washington's Barbara J. Trask. Chromosome ends served as "hot spots" for generating DNA disparities among primate species, the scientists propose.

Intriguingly, mutations on the chimp Y chromosome have led to the inactivation of several genes, but no comparable mutations exist on the human Y chromosome, report David C. Page of the Massachusetts Institute of Technology and his colleagues. The researchers speculate that increasing inactivation of the chimp Y chromosome is linked to their high-volume sperm production and fierce competition to impregnate receptive females.

In yet another finding, Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his coworkers discovered that genes active in the brain have accumulated more changes in people than in chimps. Alterations of regulatory genes and protein-making genes have shaped human-brain evolution in equal measure, the scientists also conclude.

In related news, anthropologists have found in Kenya the first fossil of a chimp ancestor. The scientists unearthed three 500,000-year-old teeth that resemble those of common chimps today, report Sally McBrearty of the University of Connecticut in Storrs and Nina G. Jablonski of the California Academy of Sciences in San Francisco.

Fossils of a human ancestor, perhaps Homo erectus, come from the same ancient soil layer that the teeth did. Human and chimp ancestors apparently lived side by side, the scientists conclude.

That's possible, but fossils from the same soil layer also could represent creatures that inhabited the area at different times, notes Jay Kelley of the University of Illinois at Chicago.