In their broadest senses sociobiology and bio sociology refer to the modern study of biology as it relates within a Darwinian framework to social behavior.
Sociobiology introduced theoretical problem with its focus on ultimate causes of human nature, ignoring those proximate mechanisms through which behavior operates. A well-known example is the selectionist theory of sex differences in mating strategy. Males produce offspring with an ejaculation; females must invest a prolonged period pregnancy and nursing. Therefore males maximize genetic fitness (i.e., the representation of their genes in succeeding generations) by indiscriminately spreading their seed among many females, whereas females are selective, devoting their limited pregnancies to the finest sires and, if feasible, withholding sexual favors until they receive from the male a commitment for child support.
Bio sociology largely abjures speculations about ultimate causes, evolved in the unknowable past. Instead the focus is on proximate causes, e.g., the neuro hormonal mechanisms underlying human behavior. Bio sociology emphasizes that human behavior follows a primate pattern and therefore values comparative studies of other primate species, whereas analogs with insects, birds, and fish are regarded as too distant to be useful. Bio sociology's research methods are diverse but usually have a tight link to theory.