Not many hold this view seriously. Even evolutionists choose not to live in such a world. Instead, they philosophically smuggle Christian ethics arbitrarily into their system and hold it romantically upon their naturalistic base. If we are to have ethics, we must find them outside the natural realm. The grand result of the Kinsey Report on American sexual ethics in the 1950's was that people bought the idea that if a majority of citizens accepted something as right or wrong, it was.
Cultural relativism claims to be based on a scientific view of morals.
Admittedly, statistical analysis of human behavior is the true and proper task of sociologists. But within the discipline, unfortunately, there is, by design, or by inference, a strong tendency to make value judgments about the results of research. Sociology exists only to tell us what people are doing, not what they should be doing. True values must be found somewhere else. Ethics by majority may actually have little to do with morality.