A 3,000-year record from 52 of the world's oldest trees shows that California's western Sierra Nevada was droughty and often fiery from 800 to 1300, according to new research.

Previously unobservable events occurring between insemination and fertilization are the subject of a groundbreaking new article in Science magazine (March 18) by Mollie Manier, John Belote and Scott Pitnick, professors of biology in Syracuse University's College of Arts and Sciences. By genetically altering fruit flies so that the heads of their sperm were fluorescent green or red, Belote and his colleagues were able to observe in striking detail what happens to live sperm inside the female. The findings may have huge implications for the fields of reproductive biology, sexual selection and speciation.

Once the human genome was sequenced in 2001, the hunt was on for the genes that make each of us unique. But scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, and Yale and Stanford Universities in the USA, have found that we differ from each other mainly because of differences not in our genes, but in how they're regulated – turned on or off, for instance. In a study published today in Science, they are the first to compare entire human genomes and determine which changes in the stretches of DNA that lie between genes make gene regulation vary from one person to the next. Their findings hail a new way of thinking about ourselves and our diseases.

A team of researchers at MIT and the University of California at San Diego has shown how cell division in a type of bacteria known as cyanobacteria is controlled by the same kind of circadian rhythms that govern human sleep patterns.

Patients seen at private facilities reimbursed by Medicare were more than 550 percent more likely to have routine cataract surgery than those who received their care from the Department of Veterans Affairs, a strong indication that the frequency of cataract surgery may be responsive to financial incentives to either or both the medical facility and the physicians who perform the procedure.