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Tuesday, June 23, 2009

Today in the News (June 23, 2009)

Evolution

News can be like buses: you wait bloody ages for one to arrive, and then three four arrive at once! So, here are three four news items from Science Daily (June 23, 2009):

Social Competition May Be Reason For Bigger Brain

For the past 2 million years, the size of the human brain has tripled, growing much faster than other mammals. Examining the reasons for human brain expansion, University of Missouri researchers studied three common hypotheses for brain growth: climate change, ecological demands and social competition. The team found that social competition is the major cause of increased cranial capacity.

To test the three hypotheses, MU researchers collected data from 153 hominid (humans and our ancestors) skulls from the past 2 million years. Examining the locations and global climate changes at the time the fossil was dated, the number of parasites in the region and estimated population density in the areas where the skulls were found, the researchers discovered that population density had the biggest effect on skull size and thus cranial capacity.

"Our findings suggest brain size increases the most in areas with larger populations and this almost certainly increased the intensity of social competition," said David Geary, Curator's Professor and Thomas Jefferson Professor of Psychosocial Sciences in the MU College of Arts and Science. "When humans had to compete for necessities and social status, which allowed better access to these necessities, bigger brains provided an advantage."

The researchers also found some credibility to the climate-change hypothesis, which assumes that global climate change and migrations away from the equator resulted in humans becoming better at coping with climate change. But the importance of coping with climate was much smaller than the importance of coping with other people.

"Brains are metabolically expensive, meaning they take lots of time and energy to develop and maintain, making it so important to understand why our brains continued to evolve faster than other animals," said Drew Bailey, MU graduate student and co-author of the study. "Our research tells us that competition, whether healthy or not, sets the stage for brain evolution."

More from ScienceDaily (June 23, 2009):

54-million-year-old Skull Reveals Early Evolution Of Primate Brains

Researchers at the University of Florida and the University of Winnipeg have developed the first detailed images of a primitive primate brain, unexpectedly revealing that cousins of our earliest ancestors relied on smell more than sight.

The analysis of a well-preserved skull from 54 million years ago contradicts some common assumptions about brain structure and evolution in the first primates. The study also narrows the possibilities for what caused primates to evolve larger brain sizes. The study is scheduled to appear online the week of June 22 in the Proceedings of the National Academy of Sciences.

The skull belongs to a group of primitive primates known as Plesiadapiforms, which evolved in the 10 million years between the extinction of the dinosaurs and the first traceable ancestors of modern primates. The 1.5-inch-long skull was found fully intact, allowing researchers to make the first virtual mold of a primitive primate brain. [...]

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Even more from ScienceDaily (June 23, 2009):

How Big A Role Does Chance Play In The History Of Life?

If the broad evolutionary diversification of a group of organisms were repeated by a few species in a single genus tens of millions of years after the group's initial diversification, what would that say about the roles of contingency, constraint, and adaptation?

As Darwin observed, natural selection leading to adaptation of individuals and populations is occurring gradually and all the time. But over very long spans of time, the major channels of genetic organization, organism form, and the different ways organisms develop arose as outcomes of history-dependent variation that is now channeled, or constrained, within different groups of organisms.

For example, most cats look like cats, develop like cats, but have a fossil record that begins from less than cat-like ancestors. So do snails, and crabs, and so on. But what if the broad evolutionary diversification of one of these groups were repeated by a few species in a single genus tens of millions of years after that initial diversification? What would that say about the roles of contingency, constraint, and adaptation? In other words, how big is the role of chance in the history of life?

An international team of researchers including Field Museum curator Scott Lidgard, PhD, has discovered a group of closely related living species that independently repeated the different step-like changes that occurred in the major diversification of their kind during the Cretaceous Period, roughly 100 to 90 million years ago. But this group of species arose 80 million years later! [...]

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Autism

The subject of autism is usually the department of my brother-in-arms, Larian LeQuella, because of his own personal interest; however, since he is pre-occupied with more important matters, I will fill-in for him. So, I stumbled upon this article in Science Daily (June 23, 2009) that may be of interest to concerned parties:

ADHD Genes Found, Known To Play Roles In Neurodevelopment

Pediatric researchers have identified hundreds of gene variations that occur more frequently in children with attention-deficit hyperactivity disorder (ADHD) than in children without ADHD. Many of those genes were already known to be important for learning, behavior, brain function and neurodevelopment, but had not been previously associated with ADHD.

"Because the gene alterations we found are involved in the development of the nervous system, they may eventually guide researchers to better targets in designing early intervention for children with ADHD," said lead author Josephine Elia, M.D., a psychiatrist and ADHD expert at The Children's Hospital of Philadelphia.

Unlike changes to single DNA bases, called SNPs or "snips," the alterations examined in the current study are broader changes in structure. Called copy number variations (CNVs), they are missing or repeated stretches of DNA. CNVs have recently been found to play significant roles in many diseases, including autism [Editor: my emphasis] and schizophrenia. Everyone has CNVs in their DNA, but not all of the variations occur in locations that affect the function of a gene. The current study is the first to investigate the role of CNVs in ADHD.

Individually, each CNV may be rare, but taken together, a combination of changes in crucial regions may interact to raise an individual's risk for a specific disease. "When we began this study in 2003, we expected to find a handful of genes that predispose a child to ADHD," said study co-leader Peter S. White, Ph.D., a molecular geneticist and director of the Center for Biomedical Informatics at Children's Hospital. "Instead, there may be hundreds of genes involved, only some of which are changed in each person. But if those genes act on similar pathways, you may end up with a similar result—ADHD. This may also help to explain why children with ADHD often present clinically with slightly different symptoms." [...]

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