The post I made earlier has kept rattling around in my head... so I figured putting it down here would let me get to more relevant notes. What follows is a train of thought that has been stewing for 19 years, so before you start throwing stones at me, think about it for a bit - as I've gotten pretty good at catching them and winging them back. lol
Having said that, flame away - please! A hypothesis can only be improved with repeated attempts to discredit it.
The Nature of Love - the beginning
Let us picture two cave-persons (we'll get the PC crap out of the way now! :-)): Dik and Jan (extraneous letters having not been invented yet). Nature being what She is (a bitch), it was crucially important that she at least give these poor bastards a chance to make it in the world (having tricked them into evolving w/o the benefit of big teeth at all). So, here were her choices:
1) Make Dik the protector
2) Make Jan the protector
3) Have them share the duty equally
Not being an idiot, Nature pretty much figured out that a shortage of Diks wouldn't nearly be as much trouble as a shortage of Jans. After all, one Dik can impregnate several Jans, whereas its a bit trickier to have each Jan produce a child to each Dik that screws her.
So, Dik drew the short straw. "Poof," Nature said (she always liked the word "poof"), and Dik gained the glory that was Testosterone. It put a lot of stress on the body, causing extra wear'n'tear on the heart, etc, but boy did it work wonders against bears. Spacial Perception was augmented (quickly keeping track of where allies are and where enemies are), reflexes were boosted (dodge that swipe!), and musculature was increased (new improved Spear 2.0, with larger stone tip!).
The price for this new found power? Dik dies. Early and Often. Even if Dik survives the bears and clashes with other tribes, his later descendants won't live much past 70 because of heart-attacks and strokes. This is okay though... because:
1) primitive Dik won't make it to his 60s... by the time is reflexes slow a bit (30s), he'll be bear-food.
2) the few Diks that make it back to the tribe can impregnate all the Jans. Hooray!
Where is Jan during all this warfare? Doing the real job(s): maintaining the tribe, feeding the tribe, raising the tribe, etc. In doing this, Jan needs heightened social perception (seeing lines of interpersonal connectivity) and innate language skills (for assuaging conflict). On top of this, Nature gives her better fine motor control (detail work) and an increased resistance to infection (childbirth isn't pretty).
The price Jan has to pay for all this is pretty self-explanatory: she has to put up with Dik. At first, this was probably easily done, especially with all the bears around. Later generations won't have it so easy.
The Nature of Love - the point of the above rambling
Dik's job is pretty stressful. Dik needs reassurance that throwing himself against bears every day is worthwhile. Dik needs to *believe* that he can kill bears (Heinlein: "Some Delusions are functional"). What Dik needs, basically, is motivation.
Jan's job isn't apple-pie either. The day-to-day business of not only training the next generation of cave-persons, but the stress of keeping all those testosterone-laced Diks occupied and out-of-trouble when the bears aren't prowling was probably pretty damn grueling. There was another problem: Jan was, by the very nature of her biology, pretty much stuck with the kids. Nature (being the bitch that she is) made it pretty clear that once those babies were born, hormones would lock poor Jan's brain around them. Nature (remember: bitch) also made it pretty clear to the bears that the squealing sound babies made meant (in the bear-tongue) "free-food." Jan quickly realized that having a Dik around was pretty damn useful. Preferably a big Dik. More preferably a big Dik that wouldn't leave when a prettier, younger, friendlier (etcetera etcetera ad nauseum) Jan came around.
Back to Dik. Dik needed motivation, remember? Having a girl to come home to after a long tour of having spears thrown at oneself is pretty damn good motivation to do a good job. The problem is that other Diks are constantly vying for each others Jan. So Dik is left with a conundrum (and most Diks aren't terribly good at conundrums that don't involving strategy, tactics and/or brute-force): Go to war to impress her and then lose her to another dastardly Dik, or stay and keep tabs on her and lose her to a more impressive Dik. The solution (what little of a solution there is... but Dik is pretty simple this way) is that Dik really needs to get laid. Sex is fun. Preferably lots of it very, very often. Nature made sure to instill a healthy sex-drive in Dik, just in case a lot of other Diks didn't come back from that last raid (lots and lots of lonely Jans). Another important point: Killing bears is scary. Very scary in fact. Facing down other just-as-large Diks with strange face-paint is pretty damn scary too. Dik needs his ego stroked. A lot. Dik needs to *believe* that he is Nature's Gift to Bear-Killing... so much so that his Jan back home wouldn't dream of leaving for another Dik as soon as his side of the bear-fur rug has cooled down.
Back to Jan. Remember Jan? You know, the Jan who really can't take time out of gathering food for the little ones to exercise 4x a day and practice with the spear? Yep, that's the one. She's also the one who doesn't want to wait for months for her Dik to come home, only to get eaten because her Dik found another Jan across the cave-condo lot. So she needs to know that her Dik is effective, and nothing says "I can kill bears" better than, well... a pile of dead bears. Jan likes piles of dead bears, preferably properly skinned, tanned, and lining her cave. She also needs to be confident that her Dik isn't going to leave her and her squealing bear-foo... er, I mean, babies high and dry... although her Dik might have a harder time proving this one to her, let us assume that it can be done.
Nature needs a way to make sure that these two stick together. The solution: Love
The Nature of Love - the point (part 2)... really! this time I mean it!!
Men fall in love because of Sex and Ego
Women fall in love because of Trust and Security
I don't care what guy you find. If a girl puts out and makes him feel like a god, he will, despite himself, fall in love. Have you ever seen a guy with a girl that that makes you wonder 'why the hell is he with her??' Odds are, she makes him feel good about himself (or at one point did so) and has sex with him on a relatively routine basis (or at one point did so). I strongly suspect (this part of the theory is pretty loose still!), that if our random girl maintains just ONE of these qualities, she can KEEP a guy in love with her, or at least can until another girl promises (or provides) both again. Stop doing both and Mr. Random Guy will start looking on his own.
I also don't care what girl you find. If she finds that she feels secure around a guy (whether it be his skill, cash, fame, prowess, stature, etc.), and if she feels that she can trust him, she's hooked - and most likely will be hooked before she knows it herself. Again, I strongly suspect that if Mr. Dik maintains just one of them, she won't leave (battered wife syndrome), but if he loses both... she's outta there.
The Nature of Love - Conclusion
I don't think this belittles the concept of Love whatsoever. It's just a tool, to be used for good or evil.
Unfortunately, I feel that its been used for evil far more often. Diks and Jans have been using it for evil purposes for far longer than they picked up the "c" and "e" in their names... we all know the man who showers a girl with money, tells some pretty lies to get her to trust him, and get BAM... he gets what he wants and is outta there. We also know the woman who will stroke a man's ego and give him subtle (and not so subtle) promises of sex and thus milk him dry of everything he owns.
If we keep the Nature of Love to heart however, we can help our relationships grow far more easily than we would if we kept fumbling in the dark... as many of us do.
Guys? When was the last time you *consciously* tried to make your woman feel secure? When last did you make a small, subtle promise just so you could keep it?
Girls? When did you last tell your guy how strong/smart/skilled/etc he was? How long has it been since you winked at him just the right way?
Both: I don't care if you did that last year (or eight years ago) till you were blue... do it again today. And again next week - maybe twice.
Read the above bold-faced section again.
Random Addendum
Try it. Oh, and I'm assuming gays and lesbians are generally smart enough to configure the above advice to fit them. I haven't forgotten about hermaphrodites either (Nature knows they're marginalized enough)... although I suppose you'd either need all four factors (sex, ego, trust, and security) or find which gender they lean towards. I strongly suspect that TVs fall under their birth gender, whereas TSs fall under the augmented gender, although I haven't put nearly as much thought behind it. Also, please notice I haven't mentioned anything about being attractive. Attractive equates in the primitive mind as "healthy" and "good genes for my offspring" and has nearly *everything* to do with lust, and nearly nothing to do with love. Sure it helps get the relationship started... but nothing will grow out of the infatuation (lust based) unless our four factors are present.