Why do humans deteriorate with age? It’s a biological puzzle

Some species live for a very long time, others more fleeting. Bristlecone pines have remarkable life spans of around 5,000 years and in the animal kingdom, creatures like elephants, whales and tortoises are comparatively long lived. Some of these even achieve individual fame; Harriet, one of the Galapagos tortoises supposedly collected by Darwin himself in 1835, died in 2006 having reached the astonishing age of 175. At the other end of the spectrum, creatures such as the mayfly or annual plants live for just a day or a year. The lifespan of modern humans can exceed 100 years. This puts us somewhere in the middle.