Your Blood Vessels Could Circle Earth Four Times Laid end to end, an adult's blood vessels could circle Earth's equator four ...

The human body is a machine whose many parts – from the microscopic details of our cells to our limbs, eyes, liver and brain – have been assembled in fits and starts over the four billion years of our ...

What is human nature? This is a question that has perplexed philosophers and psychologists throughout the ages. Are people essentially socially constructive and altruistic or are they destructive and ...