Here is a brief I wrote for my philosophy of biology capstone last semester.
Moral Philosophy as Applied Science by Michael Ruse and Edward O. Wilson
Ruse and Wilson encourage more study in the area of ethical beliefs and behavior as a scientific (specifically biology and psychology) endeavor, not just a philosophical endeavor.
Evolutionary and brain science is essential to advance the study of moral beliefs, behavior, and truth beyond what philosophers themselves can do without appealing to science. Moral realism, as espoused by most philosophers, is wrong.
Ruse and Wilson (which I’ll abbreviate as R&W) start by describing our fully biological origins. We come from a long process of mutation, inheritance, and natural selection. Since we are fully biological beings with a biological origin, our moral beliefs and behaviors have also come about by a process of natural selection selecting the beneficial traits. If this is the case, studying the brain can help us understand the foundations for morality and help advance our understanding of what is good and what is not. Why, then, does the philosopher insist that ethics should be detached from our biology, that it is something extrasomatic? There are two consequences to this idea. 1) Since morality is based in the human brain and not in some external, objective moral law, moral realism is false. An alien species can develop completely different moral beliefs than humans. 2) Even if moral realism is true and there is objective morality independent of the brain, it is a mystery how we can know the existence of such truths, since these truths would not be physical. Their insistence that there are no extrasomatic moral truths does not follow from the discoveries in science, so their argument is unconvincing. However, the epistemological issue of how one can know a moral law is more powerful and one that I would like to see explored more, but the paper was not specifically about that.
While many argue that basing morality on an evolutionary history is not tenable, R&W give examples showing how moral behavior can be developed by natural selection. While “nature red in tooth and claw” is true in many cases, natural selection can also promote altruistic behavior to help a species survive. A mechanism called kin selection can select for cooperative behavior among individuals who sacrifice themselves for their close relatives. While the cooperative individual might not be benefited, the population will. Another one is reciprocal altruism, where one party will help members of another party with the expectation that the other party will help them back, and vice versa. An example that uses both biology and culture is on the taboo of incest. Incest leads to offspring with much lower fitness levels, and there is a period in the first six years of life where children who are exposed to each other every day are not able to develop a sexual attraction for each other at adulthood. This time in the first six years, as well as societal prohibitions against the behavior, lead to the almost universal (among humans) conviction that incest is wrong.
The biological and psychological study of morality can be beneficial. It seems uncontroversial that philosophers can use facts about humans to hone ethical beliefs. For example, ethicists who believe that causing harm to humans is wrong can benefit from psychological studies on what behaviors or life experiences cause subtle, but real damage to our minds. Some facts, like the fact that incest leads to less fit offspring, can add an extra element of prudence to moral behavior as well. However, R&W do not take care of the is/ought question. The fact that incest leads to unfit offspring by itself does not lead to the premise that incest ought not happen.