But ageing and death then happens in two ways – the accumulation of negative mutations because of weak natural selection and mutations that might have been advantageous for reproduction but which become negative for a long life.

One example of the latter could be the BRCA gene mutations. These are known to significantly increase the risk of breast and ovarian cancers, but have also been linked to higher fertility in women who carry the mutations. So, it could be the case that the BRCA gene mutations offer a reproductive advantage earlier in life, followed by a greater health risk later in life. But because natural selection weakens after sexual maturity, the reproductive advantage outweighs the disadvantage.

“Whatever happens earlier in life is going to outweigh whatever happens after the age of reproduction, because reproductive potential is really what matters,” says Kaitlin McHugh, a biologist from Oregon State University.

Cell senescence, where cells stop dividing, might be another example of an early-life advantage that has a late-life disadvantage. Senescence protects us against cancer because it can prevent a cell with DNA damage from multiplying. Later in life, however, senescent cells can accumulate in tissues, causing damage and inflammation, and are precursors to age-related illnesses.

Although most species do age, there are some exceptions. Many plants show “negligible senescence”, for example, and some species have been known to live for thousands of years. One particularly curious example is the pando tree in Fishlake National Forest in Utah. The tree is actually a colony of genetically identical male quaking aspen trees joined by a single root system. It covers an area of more than 100 acres (400,000 sq m) and is estimated to weigh more than 6613 tons (6,000 tonnes). Some estimates suggest it could be more than 10,000 years old.

A relative of the hydra, the immortal jellyfish, has another ingenious way of ensuring longevity – it is able to revert from its adult life stage to its early polyp stage if it is hurt, diseased or stressed. “Though at a certain point, you have to ask yourself is it the same individual or something different?” says McHugh.