It’s worth putting foremost that here I refer to consensual incest only. Incest is taboo and illegal in most societies of world except perhaps in some aborigine ones. Reasons for that that I gather from various readings, reflections and discussions are:
- ‘Yuck’ (disgust) factor
- Increased chances of genetically defective offsprings
- Social awkwardness following failed incestuous relationship
- Damaging effect on social & familial structure
First is, perhaps, ironically, the strongest as well as the weakest reason against. The strongest because this feeling of incest-being-wrong is so deep rooted in almost everybody’s psyche that mountains of rational analysis proving otherwise will be discarded instantaneously based on gut feeling of wrongness. I too harbour that disgust towards incestuous relationship. Yet, it’s also the weakest because, despite my admission in previous sentence, I must admit that yuck-ness has never been force enough to stop change in social setup, primarily because it is too personal and without reason. It can be easily argued that those that harbour disgust are free to avoid this and those that don’t are free to do so, as long as in private, as sex has always been, and that former have no locus standi in interfering matters of later. There was a time when inter-caste, inter-religious and inter-racial relationships aroused the strong yuck-ness that we observe against incest today, and we are well aware of current situation in those respects. Even now, large segment of Indian population and significant segment of world population feels yuck-ness towards homosexuality. Despite that move towards normalization is getting stronger everyday. One may find many such examples across the world which weakens feeling of disgust as genuine reason to outlaw incest.
Second is theoretically correct but practically unimportant reason. For one, increase in chances are infinitesimal at the best, not unlike many other deceases that a fetus may be susceptible to. (See this excellent researched article on Slate.) For another and more importantly, birth control is so easy in modern world that pregnancy can be avoided with certainty by those that are determined to do so.
Third is a minor annoyance let alone solid counter-argument against incest. If an incestuous relationship fails then couple involved may face social awkwardness because their opportunities of mutual confrontation are frequent and unavoidable in many cases — them being family members. This, however, is very much familial problem and hardly large enough to concern society to prohibit incest. Furthermore, who hasn’t encountered awkwardness in various forms in familial setup arising out of myriads of other reasons?
Fourth is perhaps one reason that is worth investigation by anthropologists and sociologists though my initial hunch suggests that even this is not sufficient enough. Evidence for this comes from varying degree of incest (if it can be so called) that’s already being practiced in various communities. In North-Indian Hindus, if I know right, marrying your first cousins is prohibited while South-Indian Hindus follow this practice. In Muslims communities, again, marrying cousins is all too common. Clearly if these communities have flourished over centuries, nothing suggests, as yet, what may befall on social structure if practice touches all family members. Point to note here, and point under discussion, is the legal and social ban on incest. It doesn't suggest in anyway that revocation of such ban will lead to prolifiration resulting in fallout in social structure.
So, precisely what’s wrong with incest? Your thoughts and opinions are invited particularly if you think I’ve skipped a valid reason against it. If only morality, an all too fluid term these days, is reason against, I think, in due course, we will surely see revocation of ban on this too, as had been case for others.