I like short articles like this that make a clear and quick point based on actual research and studies. According to the studies that the article references, on first impression of someone, we may all rank someone pretty much the same as far as their value as a romantic partner. The article calls this your mate value. But as we get to know people, our opinions about them change, including what we think about them as a potential partner.
For one of our studies, we recruited 129 heterosexual individuals across several small undergraduate classes. These individuals indicated, at both the beginning and the end of the semester, the extent to which the opposite-sex students in their class possessed a set of desirable qualities. We found that consensus dropped and uniqueness increased as these students got to know one another over time. After three months, uniqueness dominated consensus for all desirable qualities: attractiveness, vitality, warmth, potential for success and even the ability to provide a satisfying romantic relationship.
So You’re Not Desirable (NY Times)