Scientists have long been trying to figure out why early humans became bipedal, and one popular explanation has now been crossed off the list of possibilities. There was a popular notion that we started walking upright to free up our arms so we could carry objects, and babies—apes don't need to worry about this because their offspring can cling to them using their hands and feet. It's like a built-in Baby Bjorn.

But now University of Manchester researchers say the baby-carrying theory doesn't hold, mainly because supporting an infant on your hip or in your arms is too tiring to have been a legitimate factor in the transition to bipedalism.

A new low-cost, nanotech-based approach to power generation developed by researchers at Boston College and MIT could lead to cleaner-running semiconductors, air conditioners, car exhausts and more. The technique, published online yesterday in Science, uses the nanostructures to dramatically increase thermal efficiency.