Humans have to grow, hunt, and gather food, but many living things aren’t so constrained. Plants, algae and many species of bacteria can make their own sustenance through the process of photosynthesis. They harness sunlight to drive the chemical reactions in their bodies that produce sugars. Could humans ever do something similar? Could our bodies ever be altered to feed off the Sun’s energy in the same way as a plant?

As a rule, animals cannot photosynthesise, but all rules have exceptions. The latest potential deviant is the pea aphid, a foe to farmers and a friend to geneticists. Last month, Alain Robichon at the Sophia Agrobiotech Institute in France reported that the aphids use pigments called carotenoids to harvest the