Migrating birds fly in a V-formation to take advantage of the aerodynamic effects of flying behind another bird. Remarkably, birds take turns at the front despite no obvious benefit to the individual. A new study explains why they do it, and why cooperation can be a powerful evolutionary tool.
Some folks decided to study the calling habits of 5.3 million people over an 18-month period. 350 million phone calls later, they came to an almost obvious conclusion: Prepaid cellphone users make and return fewer calls than their postpaid counterparts.