Up til now, I'm interested in how sex is a major plot-thickening device. There are so many different little tools Marquez implements to get this theme across. Using animals, for instance, to reflect male dominance and rape; for instance, the dogs that accompany the English toward the beginning of the novel are aggressive and invoke fear in Ursula's great-great-grandmother. They're a symbol. The roosters: what's up with them? I feel they do pertain to the role of the male (obviously...) but I think they go beyond that. Maybe the fact that it is the male's decision as to where they go and what they do; but it's also and honor thing. Jose Arcadio Buendia slits their throats to redeem the soul of the ghost who haunts them (his manhood, his pride, perhaps?).
Sexual health seems to be defined by activity. The chastity underwear, the ancestral son with the cut off tail who bleeds to death was a VIRGIN. It seems that Marquez particularly emphasizes that without experiencing sex, one's self is basically incomplete; cannot grow and survive. It's definitely true in a bigger sense, ie, if everyone stops having sex, there's not going to be anymore everyone...
Incest. I'm not 100% sure about this one, but I thought I caught onto it a bit when Ursula was pregnant with Amaranta (I think), she sees her eldest's naked masculine body. From the English version:
"She felt a mingled sense of shame and pity: he was the first man that she had seen naked after her husband, and he was so well-equipped for life that he seemed abnormal. Ursula, pregnant for the third time, relived her newlywed terror."
Ok, so it's not incestuous per se, but it is a reaction that is wholly sexual; a realization of manhood, and her former escapism of the duties of being a 'good wife'... Hmm.