Jablonka and Lamb argue that there are multiple levels at which selection occurs: genic, epigenetic, behavioural, and, for humans, symbolic. Human behavioural epigenetics is becoming a hot new research field. Examples of epigenetic and behavioural selection abound in recent ethological research, from honey-bees and dung beetles to sticklebacks and snakes. For instance, if pregnant rabbits are fed on a diet containing strongly flavoured foods, and continue to eat it while nursing their young, the young in their turn will prefer the same flavours, and in turn pass the preference on to their own young across several generations without the requirement for a change in genes. Given enough time, chance mutation may enable the genes to catch up with and consolidate such phenotypic change. The same is true for socially learned skills – from monkeys in Japan learning to wash potatoes before eating them to blue tits learning to open the aluminium foil tops of milk bottles delivered to British doorsteps in the 1950s to get at the cream. These socially learned skills too are transmitted across generations among the monkey and tit populations – but in the case of the tits were lost again when foil-topped milk deliveries became obsolete in the 1970s.