Some people like to think there's something fated about who we fall in love with. It's that perfect mix of attraction, compatibility, and of course timing. But in some cases, fate may be taking its cues from birth control pills.

First, let's go over a woman's cycle and how that affects attraction. When women are ovulating, their features change in ways that men unconsciously pick up. So men are particularly attracted to women when they're fertile. And it works the other way, too. When a woman is fertile, she's more attracted to men with more traditionally masculine features and who are genetically dissimilar to her, or more compatible in terms of procreating.

Of course oral contraception changes a woman's hormonal cycles. Her body thinks it's pregnant and doesn't go through ovulation-induced changes. And in a study published this month in the journal Trends in Ecology and Evolution, researchers say that women on the pill do not show the ovulation-induced attraction to genetically dissimilar partners. So they might be choosing men who are more genetically similar-which could lead to some of the problems with conception that have become increasingly common. Because attraction isn't fate. It's chemistry.

很多人倾向于认为爱由天注定，需要一系列的相互吸引和共同语言，当然还有恰当的时机。但，在某些情况下，避孕药就能搞乱所谓的命中注定。

首先，让我们来看看女性的生理周期是如何影响她们的魅力的。当女性处于排卵期，男性在不知不觉中就能捕捉到她们体征上的一些变化，并为之吸引。反过来，当一位女性处于排卵期时，她也更容易被那些具有阳刚特征的男性所吸引，这主要是基于生育后代的考量，那些与自身基因具有较大差异的异性更受欢迎。

众所周知，口服避孕药能改变女性的内分泌。当服用过避孕药，药物中的孕激素使得女性卵巢停止排卵，也就不能发生上诉的效应。在本月出版的《生态学与进化动向》期刊上的一份研究报告里，研究者们声称，服用避孕药的女性并未对与自身基因具有较大差异的男性显示出特别的吸引力。类似的，这些服用避孕药的女性在择偶时也就不那么具有优势生殖的判断力了。由此导致的结果也越来越为人所知，也就是人种的退化。看来，爱情这东西，才不是什么缘分天定，而是一道化学分子式。