Q What happens to the billions of atoms in our body when we die? asks Victor Correa

A Put frankly, they end up all over the place. Once you die, the process/es of decomposition begin in which the vast array of molecules that make up your body, from fats to DNA, are broken down and their atoms incorporated into new molecules. Hence your carbon atoms might, temporarily, be found in a bacterium’s cell wall or combine with oxygen and be released in the CO2 of a rat’s breath. It’s all part of nature’s never-ending recycling system that is born of the law of the conservation of matter. Each element has a slightly different biogeochemical ‘cycle” – the carbon and nitrogen cycles being the stuff of school textbooks – but the upshot is that all of our atoms are incorporated into a huge array of other organisms and materials in a ceaseless game of pass the parcel. The ultimate origin of the vast array of elements is equally astonishing, formed as they were in the bellies of stars and in spectacular supernovae. As Carl Sagan so memorably put it: ‘We’re made of star-stuff.”

Q Is there an evolutionary explanation for the hypnagogic jerk […]