Wellcome Trust-funded researcher Professor Anita Thapar has developed a new model for disentangling whether a particular behaviour is genetic or environmental in origin.

She studies children conceived through IVF, who may be genetically related to either both parents, or just the mother or father, and children born by surrogacy who are not related to either parents.

An intriguing finding was that the children of mothers who smoked during pregnancy were more likely to develop anti-social behaviour - but only if they were directly related to the mother. Surprisingly then, the effect is purely genetic (the same genes that stress the mother and cause her to smoke are influencing the child's behaviour), and not the result of toxins in the smoke affecting the fetus, as had previously been thought. 

It appears that although we can modify the effects of our genes through our choices and environment, and through medical interventions where necessary, the genetic imprint we get from our families plays a significant role in shaping our identities - long before we are even conscious that we are alive.