Stages in the Evolution of Modern Humans
A convenient place to begin a brief history of the human lineage is with the placental mammals—hairy, sweaty, toothed, lidded, flap-eared four-limbed animals with lungs, four-chambered hearts and developed brains. They maintain a high constant body temperature. Their young are produced from embryos attached to the placental organ in the uterus and, after birth, are nourished by milk from mammary glands. The oldest fossil of a placental mammal, dated to c.125 Mya (million years ago), is a ‘dormouse-like creature’ 10 cm long.