150 million years ago, new animals emerged that stayed around to look after their newborns; mammals revolutionised childcare. A few primitive mammals still have eggs, but when echidnas and platypus emerge, they feed directly from their mother’s skin. All mammals start on milk. Suckling is one of mother nature’s great inventions and with food on tap, fathers lose another job - they’re no help. Instead, a remarkable bond forms between baby and mother. Milk can sustain increasingly helpless young, born at any time of year.