Running speed and strength depends on the type of muscular tissue one is born with.
Skeletal muscles are attached to bone structures and cannot stay long in a flexed position without depleting their energy reserves.
Why are there males and females? Why are there two sexes instead of three, or twelve, or one?
Ever wondered if Olympic athletes are trully gifted genetically? Or does all their success come purely from hard work?
Until recently, scientists believed that domestic dogs originated in the Middle East. But reports suggest that almost all domestic dogs began in East Asia as the offspring of three lineages. Virtually all domesticated dogs in the United States descend from dogs brought over by ancient people that crossed the Bering land bridge from Asia to North America.