CMV: The most common evolutionary (sometimes evopsych) argument for male cheating being a far lower genetic threat is not very strong

My understanding of the strongest version of the most common form of this argument is something like this:

If a woman cheats, she risks becoming pregnant with another man. Accordingly, her main partner risks devoting his life and resources to kids that aren’t genetically his, and his bloodline may die out. In comparison, a man who cheats can still have kids with his main female partner, preserving her bloodline. It is therefore worse for women to cheat, because her actions fundamentally lower his long term reproductive success to a much higher degree than he is likely to lower hers if he cheats.

However, there are many problems with this argument, including:

1. Firstly, as a general framework, the evolutionary argument depends on traits and genetics surviving in the long term. If a cheating man still has kids with his main female partner, but the quality of life for those kids or their kids or their kids suffers as a result and affects their reproductive success (particularly for sons), that poses just as real a threat to her genetics being passed down long enough to be evolutionarily relevant.

2. To extend on the above, we know that there is a very real success of cheating affecting the innocent woman’s childrearing: Men get attached to other women all the time and divert resources and love and effort from their primary relationship. Men become fearful their secret will be exposed and give huge amounts to their illicit partner trying to keep it hush. Women who discover their partner has cheated often divorce him (at the very least under massive social expectations and judgement) and lose tax benefits and supplementary income. And so on. There are clearly a huge range of ways in which cheating can have a flow on effect hurting her relationship and available resources, therefore her kids' development, and therefore her genetic potential.

3. Consider also that men making these arguments also often believe that beta males are at severe risk of not passing their bloodline on further. If you believe that environment and nurture remotely shape personality, it is easy to see how a cheating and absent father, and a depressed single mother, could very well raise sons with suppressed or unattractive personalities incapable of finding a partner; therefore destroying the mother’s bloodline, too, even if she produced kids herself.

4. If the man becomes sufficiently attached to another woman before he’s had kids with his primary partner, there is a real risk that relationship develops a dead bedroom and she does not have kids at all, or delays them substantially (hoping the relationship can be repaired and potentially not knowing his attention is elsewhere permanently), thus affecting her fertility. Ultimately, a woman only has full control over reproduction once she is pregnant; it is still contingent on a man to choose her to impregnate in the first place, and there is a real risk that a cheating man will decline to sleep with her (at least often enough to ensure pregnancy), placing her in a very difficult situation of deciding whether to stay or try another man while her fertility is declining.

5. Even in the best case, where the man is not attached to another woman at all and diverts no resources from his primary relationship, all sex with a new partner has a non-zero risk of sexual health measures failing or breaking and an STD being carried back to the primary relationship. It is not uncommon for STDs to affect or delay fertility.

6. Men and women tend to pair within <6 years of each other or so, but the male fertility curve is substantially more generous to aging men than to aging women. If a couple has kids on the later side when he is 35, even if it takes him five years to discover she cheated and they aren't his, he actually still stands a very reasonable shot at finding another partner and having his own children. Unless the secret is hidden successfully until he is infertile or it is completely infeasible to find another childbearing partner in time, his genetic odds are poor but not zero. Conversely, a woman stuck in a relationship she is trying to fix to have kids, but cannot because he cheated and has permanently shifted interest to another woman, would have a much greater risk of having a child with another man ruled out. In this sense, men have a safety margin of their own in case of paternity fraud.

7. The argument for a woman cheating being a major risk to a male bloodline is also overplayed. Obviously, yes, there is a risk he raises kids and none of them are his, and that effect is fatal to his genetic lineage. But there is also a strong likelihood that she will not fall pregnant to the illicit partner anyway, or that the kid will still be the husband's (remember, the male partner must still be having sex with her around the same time or he would know for sure the pregnancy isn’t his; so he is always guaranteed a strong chance of parenthood). It is also possible and frequent for only one child to be the product of an illicit relationship, and for the man to have still preserved his bloodline by having had a child with her before or after the affair’s child. A woman who has an illicit child is not guaranteed by any means not to have one with her husband in future.

8. Finally, any evolutionary argument simply must contend with the fact that humans are social creatures, evolved in social circumstances, and have evolved with powerful emotions and abstract thinking for a long time now. Many of the evopsych traits and cultural/tribal/societal circumstances used in these arguments only evolved under these circumstances. Accordingly, even if no direct and deterministic threats to the woman arise, a man is still accountable if he causes foreseeable damage that indirectly hurts her reproductive success through the above mechanisms. If his actions deeply embarrass her within her social circle or cause his friends to avoid her entirely, or they depress her to the point of lethargy and suicidal ideation, those represent just as legitimate threats to her social and evolutionary success as the ‘harder’ genetic threats. The level of impact or control over the impacts may vary, but an evolution-based argument simply cannot handwave off real harms based on the premise that she could still theoretically have kids with him just fine if she got over it. This is not pragmatic, and a cheating man knows this.

I think that is enough to go on for now.

To be clear in summary, the argument made isn’t that female cheating does not pose a massive evolutionary threat to men. It does, and any cheating is awful.

I am also not ruling out that if an omnipotent being could really weigh up all these risks and harms and generic outcomes, it may well decide that female cheating tends to do more harm to male reproductive success than male cheating does in return. This is possible.

But… the most common evolutionary argument for there being an extremely wide gulf in evolutionary risk posed by the two just seems very tenuous. If someone tries to extrapolate that to there also, therefore, being a wide gulf in moral excusability between the two, that seems even more absurd and short-sighted to me.

CMV — I will be out for a few hours but am obviously quite interested in engaging