If you own a birdbath, chances are you’re hosting one of evolutionary biology’s most puzzling enigmas: bdelloid rotifers. These microscopic invertebrates—widely distributed in mosses, creeks, ponds, and other freshwater repositories—abandoned sex perhaps 100 million years ago, yet have apparently diverged into nearly 400 species. Bdelloids have remained an enduring enigma in part because biologists are still debating whether the species actually exist as true evolutionary entities. And if they do, what forces determine how they diverge? In the traditional view of species diversification, interbreeding promotes cohesion within a population—maintaining the species—and barriers to interbreeding (called reproduction isolation) promote species divergence.

In its early and most critical stages, human reproduction requires precise, vital functions. The role of one sperm-delivered protein, which is crucial to the process, is being closely observed by scientists from the United States and Canada.

In 2002, when astronomers first detected cosmic gamma rays – the most energetic form of light known – coming from the constellation Cygnus they were surprised and perplexed. The region lacked the extreme electromagnetic fields that they thought were required to produce such energetic rays. But now a team of theoretical physicists propose a mechanism that can explain this mystery and may also help account for another type of cosmic ray, the high-energy nuclei that rain down on Earth in the billions.

A newly discovered small molecule called IQ-1 plays a key role in preventing embryonic stem cells from differentiating into one or more specific cell types, allowing them to instead continue growing and dividing indefinitely, according to research performed by a team of scientists who have recently joined the stem-cell research efforts at the Keck School of Medicine of the University of Southern California.

Exposing teeth to soft drinks, even for a short period of time, causes dental erosion—and prolonged exposure can lead to significant enamel loss. Root beer products, however, are non-carbonated and do not contain the acids that harm teeth, according to a study in the March/April 2007 issue of General Dentistry, the AGD's clinical, peer-reviewed journal. That might be something to consider during the next visit to the grocery store.

Consumers often consider soft drinks to be harmless, believing that the only concern is sugar content. Most choose to consume "diet" drinks to alleviate this concern. However, diet drinks contain phosphoric acid and/or citric acid and still cause dental erosion—though considerably less than their sugared counterparts.

A group of organisms that has never had sex in over 40 million years of existence has nevertheless managed to evolve into distinct species, says new research published today. The study challenges the assumption that sex is necessary for organisms to diversify and provides scientists with new insight into why species evolve in the first place.

The research, published in PLoS Biology, focuses on the study of bdelloid rotifers, microscopic aquatic animals that live in watery or occasionally wet habitats including ponds, rivers, soils, and on mosses and lichens. These tiny asexual creatures multiply by producing eggs that are genetic clones of the mother – there are no males.