"We live on a Goldilocks planet that has nurtured life as it has sailed through billions of laps around the Sun. Animals evolved from microbes that resembled sperm cells that wriggled in the sea; great apes, or hominids, were born 15 to 20 million years ago; apes like us, called hominins, arose in Africa more recently, and modern humans with fine-boned skeletons have been prancing around for less than 100,000 years. Plants assemble their tissues from carbon dioxide and the power of sunbeams, and we are energized by eating them and the flesh of animals that graze on fruits and vegetables. The digestive system releases small molecules from our food and these are propelled around the body in blood vessels to sustain every cell. The architecture and operation of the body is detailed in a cluttered instruction manual written in 20,000 genes spotted along 2 m of DNA. Construction takes nine months and includes wiring a big brain that endows the owner with a sense of self and the illusion of free will. Ageing of the body is unfaltering; after a few decades, the animal stops working and is decomposed."