The evolutionary explanation in terms of genetic fitness (kin selection) goes roughly like this: Grandchildren share 1/4 of each of their grandparent's genes (parents and siblings share 1/2), so genes that help to "code" for traits that lead you to give up X/4 amount of your fitness (your chance of reproductive success) to increase your grandchildren's fitness X amount would spread through the population more than genes that "code" for more selfish behavior. So, all else being equal, we should expect to see selection for genes that lead grandparents to be nice to their grandkids. Of course, things are messier than this. Such traits won't be selected for in organisms that disperse such that grandparents aren't near their grandkids. Conversely, since grandparents (e.g., in humans) are typically past reproductive age, genes that code for even more generosity might be selected for--that might explain why grandparents spoil their grandkids rotten! Of course, it would be hard to code for something...

Yes, at least assuming that the "other woman" knows, or should know, that the man is married. The wife has grounds, in the sense of appropriate reason, to be angry because anger is an appropriate emotional response to having an important relationship messed up (not to mention other things, such as parenting help, financial help, etc.), and appropriate targets of that anger include persons who knowingly did things to mess up that relationship (hence the wife also has at least as much grounds to be angry at her husband). I am assuming here that it is sometimes appropriate to feel anger, an assumption that might be questioned by some (e.g., Buddhists?). Whether the wife has grounds, in the sense of moral justification, to be angry at the other woman is a more complicated question, since it is not clear what it means to be morally justified to feel an emotion towards someone (and also because the facts of the case might make such justification unclear).

If by "the chemical spark has faded" you mean that you are no longer sexually attracted to him and no longer enjoy sexual relations with him, then it may be important to both of you. If you would rather be with someone with whom you want to be physical, then you will not only miss something you enjoy by staying with him, but worse, you may end up wanting to leave him if you find someone else you are physically attracted to (and whom you also find to be "a very nice guy"). And if your boyfriend is someone who enjoys sexual relations and being "wanted", then it seems you should tell him how you feel, so that you can decide together whether you should stay together (e.g., he may prefer to be with someone who is more interested in him physically). However, if you just mean that you have lost that initial spark we feel when we first start dating someone, then you are probably just like most people. That spark typically fades but without taking with it all interest in sexual relations. People often...

The statistical norm might be defined by what is true of the majority. But why on earth would we want to define the moral norm solely in terms of what the majority of people do? That would mean that, by definition, vegetarianism, atheism, and marriage between different races was wrong. It would mean that you were morally wrong if you were an abolitionist in the South or fought for equality for women in America in the early 20th century (I'm not sure when that became the majority position) or fight for equality for women in many countries today. For that matter, it would make it wrong to be a Jew or a man who goes to college or a firefighter. Perhaps what you mean is that homosexuality could be considered biologically "non-normal" (it's not clear exactly what that might mean, since whatever we do is allowed by our biology). That may not be true, depending on what one means by biologically normal. But even if it were, it would not make it morally wrong, since lots of biologically "non...

It depends on what you mean by love, but I can't think of any definition of love that would suggest it is impossible or even unlikely to fall in love with someone you interact with (a lot) on the internet. I don't think there's a (credible) scientist in the world who would say love between humans is based solely on pheromones, chemicals, and physical attraction. They might say that physical attraction, perhaps lust, is based largely on pheromones and various chemical and hormonal processes. But I think it's fair to say that, even so, people can be very physically attracted to (lust after) someone they see on the Internet (or TV or movie screen)--no pheromones detected!--and I'm sure part of that feeling of attraction has to do with the chemical and neural changes the beautiful images cause in them. (Just to take a crazy example, I suspect it is possible to feel very attracted to Catherine Zeta-Jones or George Clooney without meeting them in person--I'm just guessing here based on what other...

You seem to be beginning with the assumption that romantic love must be essentially unselfish, that people must be motivated to love their lovers for the sake of their lover (only?) and not themselves (at all?). I'm not sure why we should think that's true. Perhaps it seems that way because we normally assume that people are and should be willing to sacrifice their own interests for the people they love. And that surely is true. But those unselfish feelings and behaviors that occur within the relationship are (a) entirely consistent with falling in love for more selfish reasons, some you are aware of--the other person makes you feel good in lots of way--and others you aren't aware of--your genes dispose the development of your brain so that it picks up on features of your lover that make them appear attractive to you (there's all those studies on pheremones), and (b) entirely consistent with your continuing to get satisfaction from your relationship and that being a significant motivation...

My own brief answer is that we cannot choose to fall in love or to re-ignite love, but we can make choices that will make it more (or less) likely that we come to love someone or something. For instance, at a bare minimum, if you believe that it would be good for you to come to love someone, you need to choose to be around that person and engage with him/her; if you believe that it would be good for you to come to love watching soccer (perhaps because someone you love wants you to love watching soccer with him/her), then you need to choose to watch soccer, perhaps with that person trying to convince you what is so wonderful about it (trust me, you will come to love it!). But once you actively engage with the person or activity, it seems to me that you cannot control whether you come to have the feelings of love towards them--figuring out what those feelings are is another philosophical/psychological issue. But I think you will find better answers than mine if you look at Eric Schwitzgebel's...

I would add to Louise's eloquent response one point: autism is the name for a spectrum of mental functioning and I suspect that if your boyfriend functions in a way that you did not notice anything remarkable, then he is on what they call the "high end" of the spectrum. You should discuss with him his history and his diagnosis. You may also wish to read some of the first-person accounts of people with autism, such as Temple Grandin 's.