The effect of maternal deprivation on child development has been inferred from studying institutionalised orphans. And experimental animal models have been used extensively for studying the impact of adversity on welfare of the young. One particularly famous programme of controversial laboratory experiments carried out in the late fifties by Harry Harlow studied the lasting effects of maternal care on baby monkeys. Babies raised with comfortless wire ‘surrogate mothers’ were psychologically disturbed compared to babies whose wire ‘mothers’ were covered with a soft material they could cling to. 

It may seem obvious that the early environment has profound effects on the maturing young, and we could easily guess that traumatic or adverse early experiences would be likely to disturb the mental and even physical health of developing offspring.  But what does that adversity actually do to a developing infant’s brain or body to cause lasting disturbance?  How does the environment affect our cells and molecules enough to bring about these outward signs?  And how can these environmental effects be measured objectively?