The big, weird world of creatures inside you may be even bigger and weirder than anybody thought.

Fungi are the latest addition to human menagerie, joining bacteria and viruses in forming the teeming, biological kingdom-spanning superorganisms of our bodies.

“We were all fascinated with the diversity and sheer mass of microorganisms that live inside our intestines,” said immunobiologist David Underhill of the Cedars-Sinai Medical Center. “So we started asking: What do we know about fungus in the gut?”

In a June 8 Sciencestudy, researchers led by Underhill and postdoctoral student Ilian Iliev link gut fungus to colitis, an inflammatory bowel disease.

While the findings may be presently useful to colitis researchers, the implications are sweeping: Scientists might ask the same questions of internal fungi as they do internal bacteria, the importance of which is now a buzzing research frontier.

In the last decade, researchers have linked resident communities of bacteria — which outnumber human cells in a body by 10 to 1 — to diseases and fundamental processes, from diabetes and heart disease to metabolism and immune system function. Even viruses are in on the act.

Appreciation of this so-called microbiome represents a sea change in awareness of bacteria: No longer are they external entities that sometimes cause disease, but rather an essential, positive component of human health.

Whether fungi also play a part is a question relatively few researchers have asked. A handful of studies have suggested a limited role, primarily in skin and mouth conditions. (...)

Evolution by definition is cold and merciless: it selects for success and weeds out failure. It seems only natural to expect that such a process would simply favour genes that help themselves and not others. Yet cooperative behaviour can be observed in many areas, and humans helping each other are a common phenomenon. Thus, one of the major questions in science today is how cooperative behaviour could evolve.

Scientists from the Max Planck Institute of Evolutionary Biology in Plön, Harvard University, and the University of Amsterdam have now developed a new model combining two possible explanations - direct reciprocity and population structure - and found that both repetition and structured population are essential for the evolution of cooperation. The researchers conclude that human societies can best achieve high levels of cooperative behaviour if their individuals interact repeatedly, and if populations exhibit at least a minor degree of structure. (...)

A genetic study of cattle has claimed that all modern domesticated bovines are descended from a single herd of wild ox, which lived 10,500 years ago.

A team of geneticists from the National Museum of Natural History in France, the University of Mainz in Germany, and UCL in the UK excavated the bones of domestic cattle on archaeological sites in Iran, and then compared those to modern cows. They looked at how differences in DNA sequences could have arisen under different population history scenarios, modeled in computer simulations.

The team found that the differences that show up between the two populations could only have arisen if a relatively small number of animals - approximately 80 - had been domesticated from a now-extinct species of wild ox, known as aurochs, which roamed across Europe and Asia. Those cattle were then bred into the 1.4 billion cattle estimated by the UN to exist in mid-2011. (...)

Sometimes evolution gives and sometimes it takes away. Cats have lost their ability to taste sweets, and dolphins lost the sensors needed to pick up bitter or sweet flavors.

From studying their DNA, scientists conclude that the common ancestor we share with these fellow mammals could taste all five of the major flavor types — sweet, salty, sour, bitter, and the more recently discovered savory flavor known as umami. But after we diverged, many lost some of their tasting ability.

Researchers from Monell Chemical Senses Center recently analyzed genetic material from 12 species of mammals, all of them meat eaters, and found that seven carried completely nonfunctional versions of the genes that endow us with an appreciation of sweets. Monell researchers had already shown this was the case with domestic cats. Now the scientists have found broken sweet genes in sea lions, fur seals, Asian otters, a cat relative called the linsang, and a mongoose relative, the fossa.

This came as a surprise, said Monell biologist Gary Beauchamp, who led the project, along with Monell molecular biologist Peihua Jiang. People assumed that the ability to taste sweet things was nearly universal in mammals. It was even more surprising that dolphins couldn’t detect bitter, he said, because bitter perception is important for many animals to detect poisons. (...)