Researchers at the University of Colorado Boulder looked at DNA data for 825 (white, heterosexual) couples, focusing on single-nucleotide polymorphisms — specific points on the DNA strands that are known to vary from human to human. They compared each subject's polymorphisms to that of his or her mate and then to other (unrelated) individuals' in the study. The data showed that each subject’s DNA was more similar to that of his or her partner than to other subjects'.
But, perhaps unsurprisingly, DNA doesn't tell the whole story. The researchers compared the effect of DNA similarity to that of having comparable education levels to your partner and found an association that was three times stronger than that of having similar genes. In other words, education level was shown to be a much better indicator of whether two people were married compared to DNA similarity.
Of course, scientists already knew that we tend to be attracted to those who share like character qualities, but this is the first time researchers have tied attraction to genome similarities. But, the data only showed an association between similar genes and coupling decisions. And, the study raises more questions than it answers: How, for example, does race play into this? Does this phenomenon of DNA similarity explain the "boyfriend twins" weirdness? And, where are the "girlfriend twins"? Regardless, at least on the surface, this finding suggests that, despite our insistence otherwise, opposites might not really attract after all. (Science Daily)