Humans

Thinking big WASHINGTON — Humans may have evolved to supply the brain with the energy-storing substance creatine at the expense of other body parts. Creatine fuels metabolism by storing energy, like a battery, over the short term and releasing it quickly. Molecular evidence from frozen tissue samples suggests that, compared with chimpanzees and rhesus macaques, humans shuttle more creatine to the brain and less to skeletal muscles.