From Bruce Denness, Niton, Isle of Wight, UK
In believing that humans will still exist in billions of years, several readers attribute differing degrees of faith in our mental agility to see us through the death of the sun. However, big-brained Homo sapiens has been around for less than a million years, whereas jellyfish have chalked up over 500 million with no brain at all. So, as in some corners of society, airheads may trump brains after all (Letters, 3 February).
