But there is no such thing as change in the universe. Everything is well regulated and follows laws. We see this all around us. Ignorance of a fact does not mean that it does not exist. It is only the law of karma that explains why each individual is what he is.
Nothing happens without a cause.
Effect and cause correspond to each other. Neither heridity nor invironment, nor even their interaction, can explain the facts of life. A physical process can produce only a physical effect, nothing more. Only the body and mind of a person can be attributed to heridity and invironment. We have to seek elsewhere for an explanation for the personality of an individual.