And other news from science and technology.

(For the latest Human Nature columns on Terri Schiavo, mandatory pregnancy, and more, click here.)

A study suggests bisexuals are really gay or straight. Researchers "measured genital arousal patterns" among self-described bisexual men as they watched erotic images of women and men. "About three-quarters of the group had arousal patterns identical to those of gay men; the rest were indistinguishable from heterosexuals."

Fire ants clone themselves. Queens produce some eggs that become never-fertilized female ants. Other eggs are fertilized by males, but the paternal DNA in the embryos wipes out the maternal DNA, making them clones of their fathers. All other ants (those that have both maternal and paternal DNA) are sterile, so only the clones propagate.

NASA hit a comet with a rocket. The crash took place 83 million miles away at 23,000 miles per hour. The immediate goal was to knock some stuff out of the comet so we can learn what comets are made of. The speculative goal was to figure out how to blow up a comet if it's heading toward Earth. We achieved the first goal but not (as expected) the second.

British government ads are targeting smokers' sex lives. One ad shows a cigarette burning between two fingers made to look like legs. It asks, "Does smoking make you hard? Not if it means you can't get it up." Another ad says smoking causes "cat's bum mouth." The government argues that smoking has made as many as 120,000 British men impotent and that young smokers are more afraid of losing their sex lives than of losing their health.

Two new fronts in the Ritalin war: 1) The government is investigating a study that "found damage to the chromosomes of 12 children who took Ritalin for three months," and 2) an FDA review "of Concerta's use in children turned up more reports of psychiatric reactions than anticipated, including … suicidal thoughts, hallucinations and violent behavior." Some scientists doubt either connection.

Republicans are scrambling for a way to make stem cells without making embryos. They're talking about allocating millions of dollars quickly to fund several ideas: 1) harvesting cells from dead but usable embryos, 2) making adult cells embryonic, and 3) creating embryonic parts without whole embryos. (For Human Nature's analysis of the ideas, click here, here, here, and here.)

The scientist who led the sequencing of the human genome has launcheda project to create artificial life. Investors and the government are funding his work. The idea is to program DNA just like software. He hopes man-made organisms will manufacture drugs and clean energy. Critics fear bioterrorism and unforeseen consequences.

The European Union, the United States, and four other countries will build the world's first major nuclear fusion reactor. They're doing it because we're running out of oil, and other energy options (solar, wind, coal, nuclear fission) are inefficient or hazardous. But fusion hasn't been made cost-effective either, and "even fusion proponents concede that the process is decades away from practical use."

Your penis isn't as small as you think. In a study of men who came to doctors "complaining of a small-sized penis … penile length and girth were measured twice using a tape measure in both flaccid and fully stretched states. Every patient was informed that if his flaccid and stretched penis size was 4 cm and 7 cm or more, respectively, it was considered normal. … None of the patients had short penis according to our measurements."