• The brain makes up about 2 % of body mass but consumes 20–25 % of energy.
• Humans can run long distances thanks to sweating.

An average adult is about 1.6–1.8 m tall and usually weighs 55–85 kg; men are on average taller and heavier than women. Humans walk on two legs, have an upright posture, an opposable thumb and a brain of about 1,300–1,400 cm³. Normal adult oral body temperature is about 36.1–37.2 °C: rectal readings are 0.3–0.5 °C higher, armpit readings lower, it is lower in the morning than in the evening, and it also depends on age, activity and hormones. 37.3–38 °C is considered low-grade, from 38 °C a fever, 39–41 °C a high fever, and 41 °C and above hyperpyrexia, a medical emergency. When core temperature drops to 35 °C or below, hypothermia develops: mild at 32–35 °C, moderate at 28–32 °C and severe below 28 °C, with heart rhythm disturbances, coma and risk of death, although active rewarming can sometimes save the person.