How would a sociobiologist account for the existence of altruism?

What will be an ideal response?

The process of evolution is not really a matter of individual survival. What matters is a gene pool distributed across a population. If one group survives and reproduces at a high rate, its genes move on to subsequent generations more than other groups' genes do. In addition to individual reproduction, genes are carried forward to the next generation by anything that helps your part of the gene pool reproduce (inclusive fitness). If you do an altruistic deed for a relative, it helps the relative survive. If an altruistic act (in which you die) saves a great many of your relatives, it helps aspects of your genetic makeup to be passed on because your relatives are genetically similar to you, i.e., kin selection. Thus, the tendency to be altruistic may be genetically based.