I think there are too many unique circumstances here to make a general rule. Science/data tells us what IS, morality describes what we think we SHOULD do. Science informs
policy/morality, but does not dictate it. Science tells us that the offspring of first cousins are more likely to have genetic defects, but only by a couple of percent (compared to 3-4% to non-related partners), which is not much more than a couple in their late 30s choosing to have children. Science says nothing about marriage of first cousins, or protected sex between them. Now, first cousins, like all parents, should consider all the risk factors when contemplating having children. What percentage is too high a risk? Different people will come to different conclusions, regardless of their humanism.
A similar example is men having gay sex. Science/fact/reality show us that there is a significant risk over straight sex. We balance this with many other issues that outweigh the increased risk and don't have a moral problem with it. Similarly, most people don't have a moral issue with motorcycles even though they are significantly more dangerous than cars.
Morality is complicated, and each issue would need to be addressed individually. And different people will come to different moral conclusions, often despite their religion or lack thereof.
Bo Bennett, PhD
Social Scientist, Business Consultant
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