Ants: “I’m Not Dead Yet” Ants are notoriously efficient undertakers, carrying off dead nestmates before the corpses can infect the colony with their pathogens. Some researchers had hypothesized that ants detected breakdown products in decomposing bodies, but a new study undermines that theory. Entomologists from the University of California, Riverside, found that Argentine ants could detect dead nestmates before decomposition could have taken hold. More telling, the team found that living ants produce two “I’m not dead yet” chemicals, called dolichodial and iridomyrmecin. The compounds curb necrophoresis, the removal of dead colony members by fellow workers. Both chemicals dissipate quickly after death, plummeting to below half strength in just 10 minutes, the researchers write in a paper published in the May 19 Proceedings of the National Academy of Sciences USA. —John Matson
Working on the Railroad A single railroad crosstie may not impact the environment as much as it helps to keep rails together. But considering that millions are deteriorating around the world, the material chosen as a replacement can affect the amount of carbon dioxide (CO2) in the air. Wood crossties require harvesting a lot of CO2-absorbing trees, roughly 89,000 cubic meters of timber per million crossties; concrete versions increase greenhouse gas emissions because of the fuel consumption during their manufacture. Robert H. Crawford of the University of Melbourne in Australia concludes that making enough concrete ties to keep one kilometer of tracks aligned for 100 years generates the equivalent of 656 to 1,312 metric tons of CO2. That amount is about one-half to one-sixth the amount that timber ties contribute, because concrete versions last longer and timber releases CO2 as it decays. Track the findings in the June 1 Environmental Science & Technology. —Charles Q. Choi
Temptation Zone An imaging study reveals how the brains of some dieters stay disciplined and others give in to cravings. Researchers at the California Institute of Technology asked volunteers trying to slim down to pick a food toward which they felt neutral in terms of health and taste (many chose yogurt). They next scanned the dieters’ brains as they chose between this reference item and either healthy snacks, such as apples, or junk foods, such as candy bars. The team linked a brain region, the ventromedial prefrontal cortex, with the desire for tasty items, regardless of how unhealthy they might be. A separate area, the dorsolateral prefrontal cortex, was associated with self-control; dieters who had strong signals in this region chose the healthier food even if they did not think it tasted better. The findings, in the May 1 Science, present new targets that could help treat not only obesity but also addiction, wasteful spending, and other matters dealing with desire and restraint. —Charles Q. Choi
Humanity’s Ground Zero A massive new genetic study may have zeroed in on humanity’s starting point. By analyzing genetic sequences from 121 populations in Africa, 60 non-African populations and four African-American populations, researchers traced Africans back to 14 ancestral clusters originating at 12.5 degrees east latitude and 17.5 degrees south longitude, near the border of modern-day Angola and Namibia. Besides offering a far more specific understanding of human migrations, the study, in the May 22 Science, also promotes a better understanding of health and disease in many of these populations. —Katherine Harmon
What is Watson? This software program will beat people on the game show Jeopardy! At least, that is what IBM hopes will happen with a supercomputer running a powerful semantics-crunching program dubbed Watson, which will have access to a knowledge database but no Internet connection. In following up on its human-beating chess computer Deep Blue, IBM says it has been refining Watson for almost two years and hopes to stage a series of sparring matches before a final showdown in 2010. —John Matson
Note: This article was originally printed with the title, “News Scan Briefs.”
