It is a natural history tale that every third grader knows: The dinosaurs ruled the Earth for hundreds of millions of years, until an asteroid struck the Yucatan Peninsula and triggered a mass extinction that allowed the ancestors of today’s mammals to thrive.

The asteroid part of the story may still hold true, but a new study challenges the notion that a mass extinction of dinosaurs 65 million years ago played a major role in the dominance of today’s mammals.

A new, complete 'tree of life' tracing the history of all 4,500 mammals on Earth shows that they did not diversify as a result of the death of the dinosaurs, says new research published in Nature today.

The study was undertaken in the UK by scientists at Imperial College London and the Zoological Society of London (ZSL). It contradicts the previously accepted theory that the Mass Extinction Event (MEE) that wiped out the dinosaurs 65 million years ago prompted the rapid rise of the mammals we see on the earth today.

Tailor-made dietary fiber may be able to flush artery-clogging cholesterol from the body and lower the risk of heart disease, according to a new study by University of Guelph researchers.

The study found that a fiber-rich plant extract from a legume grown in India can reduce cholesterol in pigs. The results were published in the March issue of the Journal of Nutrition.

An interdisciplinary team of researchers at Vanderbilt University has analyzed the simplest known biological clock and figured out what makes it tick. The results of their analysis are published in the March 27 issue of the journal Public Library of Science Biology.

Biological clocks are microscopic pacemakers. They are found in everything from pond scum to human beings and appear to help organize a dizzying array of biochemical processes. A traveler experiences jet lag when his or her internal clock becomes out of synch with the environment. Seasonal Affective Disorder, some types of depression, sleep disorders and problems adjusting to changes in work cycles all can occur when an individual's biological clock acts up.

Using measurements of the four ESA's Cluster satellites, a study published this week in Nature Physics shows pioneering experimental evidence of magnetic reconnection also in turbulent 'plasma' around Earth.

Given the huge shortage of donor organs, researchers have been trying to find ways to transplant animal organs across different species (known as "xenotransplantation"), with the eventual aim of transplanting animal organs into humans. The major stumbling block, says Dr Muhammad Mohiuddin (US National Heart, Lung, and Blood Institute) in a paper in PLoS Medicine, is that the immune system in the animal receiving the organ tends to reject the transplant.

Nevertheless, the recent development of genetically modified pigs that are more compatible with humans, "has reinstated hope for the success of xenotransplantation," he says.