Despite slang terms that imply otherwise, the human penis contains no bones. The same cannot be said for many of our closest evolutionary relatives: Chimpanzees and bonobos both have penis bones (a macaque one is pictured, left), also known as bacula.

To find out why some primates have the feature whereas others don’t, researchers traced the bone’s evolutionary history through time. The baculum first evolved between 145 million and 95 million years ago, as reported in the Proceedings of the Royal Society B. That means it was present in the most recent common ancestor of all primates and carnivores. Why some descendants, like humans, lost their bacula appears to be due to differences in mating practices: In primates, the presence of a penis ...

Opals (shown above) are is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Because of its amorphous character, it is classed as a mineraloid, unlike crystalline forms of silica, which are classed as minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. Opal is the national gemstone of Australia.

The internal structure of precious opal makes it diffract light. Depending on the conditions in which it formed, it can take on many colors. The one pictured on the left is called the "Virgin Rainbow" opal, being the finest ...

Early birds and night owls have radically different daily habits. But a new study suggests they both share one trait: As the clock ticks, their decisions get dicey. Neuroscientists examined the quality of moves in more than 1 million games of chess in an online database. They charted the decisions of 99 prolific players by gauging the time they took for each move and its usefulness in leading to a victory - factors that impact games like high-speed tiebreakers in the World Chess Championships.

As expected, early risers played more games in the morning, whereas night owls were active at dusk and beyond. But both sets of players took longer for each move and made better game choices early in the day and soon after they woke up. Come evening, ...