The Human Zoo , a follow-up book by Morris that examined the behaviour of people in cities, was published in The Naked Ape , which was serialised in the Daily Mirror newspaper and has been translated into 23 languages, depicts human behaviour as largely evolved to meet the challenges of prehistoric life as a hunter see Nature versus nurture. The book was so named because out of species of monkeys and apes , only humans Homo sapiens sapiens are not covered in hair. Desmond Morris, the author, who had been the curator of mammals at London Zoo , said his book was intended to popularise and demystify science. Morris said that Homo sapiens not only have the largest brains of all higher primates, but that sexual selection in human evolution has caused humans to have the highest ratio of penis size to body mass.