Biology, however, is modified by life experience

The range of human possibilities is exceedingly broad. At the moment
of birth, each baby is neither a preformed individual whose destiny is set,
nor a blank slate whose individuality can be shaped entirely by external
forces. Children clearly differ in their genetic endowment from the time of
conception. Some actively seek out experiences and some are more inhibited.
Some cry frequently and others are better able to soothe themselves.
Some are more predictable and easy to read while others are less easily
understood. Biology, however, is modified by life experience. Depending
on the caregiving they receive and the environments they encounter, shy
children can become sociable, fearful children can become secure explorers
of their surroundings, and highly exuberant children can develop considerable
self-control. Each child’s individual capacities are both limited and
broadened by his or her genetic makeup and life circumstances. Both
operate together in influencing the probability of any given outcome