Also, there could be differences between men and women: I recall a report some time ago arguing that women overwhelmingly prefer men from their own phenotype (there were some exceptions, like black and Han women also liking white men). Instead, for men the phenotype does not matter, basically.
Yes, I remember that paper as well. It was about white women overwhelmingly preferring men of their own general phenotype, i.e. "white" men, but I think that it was that white men also prefer women of their own phenotype, but by a much smaller percentage.
As you stated upthread, I also think smell has a role to play; it may subconsciously play a role hormonally.
The paper "is" long, but they do pick apart the details. For example, instant attraction is one thing, but there are all sorts of confounding factors in "mate" choice, or marriage/long term relationship. Then, social factors might indeed come into play, such as wanting to "up" one's status, or trying to prove some ideological point, or simply just for mercenary reasons like money or security, particularly, it has to be said, where women are concerned.
Also, the "type" of person someone wants might not want them, or at least none of the ones he/she meets. So, people "settle" for someone who is willing to be with them.
I think instant attraction is something else, and much more subconscious. I don't think it's always just about a "preferred" phenotype, either. My husband, although Italian like my father, looks absolutely nothing like him. What I saw in my husband instantly, however, was not just beauty, but a sweetness, a kindness in the eyes, and strength and confidence in the face, both of which tremendously appeal to me.
After that instant attraction, all sorts of things come into play for someone like me: do we share the same values, generally and in terms of family, is this an intelligent person with whom I can have meaningful discussions, is he honest, hard working, does he have a self of humor, particularly about himself, does he come from a stable, loving family?
Sometimes, looking at the marriages around me which fall apart or are just miserably unhappy, I think they never moved to stage two, if you know what I mean, or they tried, but just aren't very good at discerning character. Or, they just married for the wrong reasons, sometimes not even being all that attracted to the person, or not really knowing them.