In this issue:
"Tales of a Stone Age Neuroscientist": By honing ax-making skills while scanning their own brains, researchers are studying how cognition evolved.
"The Neutron Enigma": Two precision experiments disagree on how long neutrons live before decaying. Does the discrepancy reflect measurement errors or point to some deeper mystery?
"The Cancer Defense": Enhancing the body's own immune system is leading to promising results in the battle against malignancy.
"Machine Life": Synthetic biologists are close to putting living cells to work diagnosing human diseases and repairing environmental damage.