Answer: Sociobiology is the doctrine that we have fundamental behaviors and psychological characteristics that are explained by the incentives present during some past period of human evolution. This is also known as "evolutionary psychology." These doctrines hold that human behavior can be explained by evolutionary analysis, and that humans act in ways that increase the probability of our genes being passed on to future generations. In technical terminology, we are thought to act to maximize our "inclusive fitness."
Many sociobiological theories focus on explaining "altruistic" behavior. This is not always what Objectivism
calls "altruism." In fact, altruism is the doctrine of self-sacrifice, of destroying oneself and one's values for the sake of others. But sometimes scholars and popular writers use the word "altruism" to mean both self-sacrifice and benevolent, non-predatory behavior. So be careful when reading about evolutionary psychology to understand what this word means to the author.
There is one basic flaw in most sociobiological theory. Quite simply, it ignores free will. Many evolutionary psychologists view human beings as essentially automatons, with no more control over their basic attitudes, values, and behavior than has a squirrel or an amoeba. But human beings are self-conscious, conceptual, volitional beings. We are able to choose what values to hold and how to act. Our ideas affect the emotions we feel.
Many sociobiologists have a simplistic view of human mental life. This explains the popularity of using simple automata (computer programs) to model human traits, as repeated game simulations do. But we can act in complex ways that depend on our own choices. Anyone who thinks, for example, that humans are inevitably inclined to protect their own offspring or genetic type needs to look at the history of the infighting in royal and imperial households (parents slaughtered their children quite often, and children slaughtered parents and siblings, for the sake of the throne and their own survival).
I am personally of the view that our genetic code defines our physical traits and contributes to certain mental aptitudes or temperaments. It is responsible for the way we experience sexual desire and pleasure, for example, at least in the most general way. But our values and abilities are also shaped by the choices we make as individuals in our own current environment. If we have weak muscles, we can exercise to be strong. If we are emotionalistic, we can learn self-discipline and logic.
Human culture is deeply shaped by the ideas people accept. Nazism and Communism are not political ideas that anyone's genes made them accept. People have been spreading altruist ethical theories for millennia, and they are deeply rooted in our culture. All religions teach them. Almost all ethical thinkers accept them. It is no surprise, then, that most people think these ideas are natural to humans, because they are so common. But we don't have to accept them, and living as we do in an industrial society organized and driven by rational thought, we have the practical means to live in different and better ways. That is for each of us to choose, by choosing to think and choosing the principles that will guide our lives.