Similarly, it is not the biological foundations, including our genes, which govern who we are and what we are like, but what we have made of ourselves on those foundations. The human person is not controlled by either external or internal forces, not pre-determined or destined, but is a responsible, responding, initiating being, becoming who they are as a result of the complex of responses, initiatives, actions and reactions which are theirs and theirs alone.

While we are subject to the power of sin, that has a hold on us only insofar as we give in to temptation, and insofar as we resist the redeeming and renewing work of Christ which gives new life to all who respond to him in faith. While we will sometimes inherit tragic and inhibiting physical characteristics as a result of our genetic makeup, even that does not control or determine who we are as people. And the fact that we do sometimes see these physiological and genetic tragedies is not the result of genes going wrong, but of human sin corrupting and distorting God’s creation. Things are not the way they were intended to be, and we cannot excuse or justify anything on the basis that it is "natural," for what we call "natural" is in actuality distorted and misshapen. We cannot factor out sin from the equation.

The response we make to whatever our biological characteristics may be is what shapes us as people. Our environment may influence that outcome to some extent, but only because it may limit our options or impinge upon us so strongly that we are overwhelmed by the strength of it. Think for example of a child growing up with two alcoholic parents. The options in life may be limited, but are not confined because of the nature of their parental home. Our lives display the way we have responded to many factors: genetic inheritance, environment, personal disposition, abilities, opportunities, relationships with others and so on. Nothing in life makes us the way we are; we have made ourselves what we now are as a result of our responses to what we have been given. How we respond to our own genetic characteristics has a strong contribution to who we are as people, both physically and emotionally.

We are who we make ourselves to be, and who we are is influenced, encouraged, and stimulated by our responses to our environment, not by the environment alone, or by genetic disposition alone. We are at the helm of our lives, not our genes. We can therefore choose whether to be moral or immoral, and we are responsible for that choice. It is not imposed upon us by our genes.

So the genetic argument for immoral behaviour is not persuasive. There is no scientific proof that we are controlled by our genes to engage in immoral behaviour, because there can be no scientific proof. We are not controlled by our genes: we have responsibility for our lives that cannot be passed off to anything else: genes, environment, or whatever. We are not driven by our genes. Biological causality is not mechanical causality: it is always the response of an organism to stimuli, not an automatic reaction. The organism can in many ways choose how to respond to the stimuli; we are not forced to respond in any particular way. Human beings in particular are called to respond in terms of their accountability to God. Ethical behaviour is a response to ethical norms which we choose to accept or violate, and we are responsible for the resulting choice. Ethics is not governed by genes. Genetic inheritance is not governed by ethics. Both are distinct but interwoven features of what it is to be human: genetically founded, ethically responsible. Ethics cannot be reduced to genetics, and to do so is to violate the nature of our humanity.

We are human beings, not vehicles for genes to replicate. Genes have no purpose save as components of human beings; they are not independent, self-directing creatures but have meaning and significance only within human beings. Genes are not alive, they have no agenda of their own to fulfil. Genes are simply chemicals, stores of biological codes, which are used by the organism of which they are a part. Genes have a part to play in the life of that organism, but they derive their existence from the life of the organism as a whole. If the organism dies, the genes no longer have a life of their own. If genes are removed from one organism, and implanted in another organism, they then become incorporated in the life of that new organism and derive their life from that. They have no purpose or life independently of the organism of which they are a part.

Human beings incorporate genetic material in their biological foundations. It is the human organism, the person, the living being, which has a purpose and a destiny, and genes are important in aiding the person to carry out that purpose. The purpose and meaning of a human being is not to serve our genes but to serve our God, who made us who we are and calls us to fulfil that calling in love and obedience.

We are sexual beings, because that is how God made us. Our genes are transmitted to the next generation by sexual reproduction. It is important that we as Christians recognise the basic motivations and desires which lie at the basis of our sexual behaviour. This is not the means by which genes can replicate themselves, but the means whereby human beings can replicate themselves. The purpose of reproduction is to bring into being another living human being, not simply to form a new gene carrier. Procreation is not the be-all and end-all of life. Thus sexuality cannot be divorced from the purpose and meaning of human life. We are created by God to serve God as the stewards of his creation, caring for it, delighting in it, enjoying it, and developing and exploring it to God’s glory. God made human beings so they could reproduce and populate the whole earth. He gave us the joy and privilege of bringing new generations into being through sexual reproduction. But God also made sexuality pleasurable, intending it to be a means of intimacy, relationship forming, bonding, comfort and leisure, to be shared by two mature people, a man and a woman, within the bounds of an exclusive, life-long, faithful commitment to each other.

Genetic drives to replicate would not need to make sexuality pleasurable. A mere animal-like instinctive urge to copulate would suffice. The genetic argument cannot explain why sex is fun, but a Christian perspective is more than adequate to do so. We are not engaged in animal-like behaviour in our sexuality. Even though we share the same biological characteristics, we are never in any way animals: we are always and in everything distinctively human. Animal behaviour can be used to some extent to understand human behaviour, but it can never explain it, for human behaviour goes beyond and above anything that any animal can ever do. We act in specifically human ways even when engaged in behaviour shared by animals; eating, drinking, having sexual intercourse. We are not animals, and cannot use animal behaviour to explain, justify or excuse the acts of human beings. We are called to ethical behaviour, something that animals cannot engage in. God gives us norms for ethical life to which we must respond, either positively or negatively.

Outside the intentions of God for sexuality, we find only distortion and destructive behaviour. If we see our sexuality only or even primarily as a means of reproduction, then any sexual activity which is not open to reproduction is wrong. Thus the Catholic church argues against contraception. If we see our sexuality only or even primarily as a means of pleasure and gratification, then any sexual behaviour which is enjoyable is acceptable. Thus casual sex, gay sex, promiscuous sex, marital infidelity, all are legitimated by such an argument. Sexuality is not simply for reproduction, not simply for pleasure, but for the bonding of a committed man and woman in marriage, thus providing the context into which children can be born and raised, with both parents being equally committed to the task. The purpose for which we have children is not to replicate our genes, not to prove our fertility, not to satisfy instinctive maternal cravings, but in response to the command of God given to all humankind: be fruitful and multiply and fill the earth.

God has given us the great task of caring for the earth, developing and exploring it. In order to carry out that task we need very many people, for the richness and extent of the creation entrusted to our care required the capability of a vast number. The gifts of hand and mind which God gives to us all are beyond telling; the fruits of our labours enormous in extent. This is why we are here; to display the greatness of God through what we have done with the world he entrusted to us, developing our own abilities to their fullest potential, becoming the people he calls us to be, so that in everyone, in everything, and in all that happens, God is glorified. All our biological characteristics, our genetic inheritance, our sexual drives, our reproductive potential, are subordinate to that great purpose. Without that, we are merely acting out our sexual urges, divorced from any true understanding of what we are doing or why. The loss of any sense of purpose or meaning is the greatest tragedy of modern life, and to seek to recover that through magnifying the significance of our genetic makeup is only to compound the tragedy.