Bowlby's theory of attachment is based on the claim that behaviours that promote reproduction are naturally selected. Genes for any behaviour tat helps us to survive or that help our genes to survive will appear in future generations. Children have an innate drive to become attached to a caregiver because attachments have long term benefits. If a child doesn't attach, they are less likely to survive and develop. Therefore, infants are born with an innate drive to attach.