At first, I am not even sure how best to frame the question in order to secure my wife’s participation.
“Would you mind taking a quick DNA test to determine our genetic compatibility?” I asked.
“Am I going to be told I have a fatal disease?” she asked.
“No,” I said. “It’s just to find out whether or not we were meant to be together.”
“Oh,” she said. “Fine. Whatever.”
On the day we each spit into separate test tubes, I do not yet understand how a DNA test can offer evidence of compatibility, because I am only on page eight of Daniel Davis’ book The Compatibility Gene.
However, here is the gist of the idea: There are a small number of human genes — a tiny section of the short arm of chromosome six — that may play a role in determining how attractive you are to a potential mate. Suitable partners can literally sniff each other out, finding an optimal genetic other half using their noses.
The basis for this notion is the so-called smelly T-shirt experiment, first performed by a Swiss zoologist called Claus Wedekind in 1994. He analyzed a particular bit of the DNA of a group of students, looking specifically at the major histocompatibility complex (MHC) genes.
The students were then split into 49 females and 44 males. The men were asked to wear plain cotton T-shirts for two nights while avoiding anything — alcohol, cologne etc — that might alter their natural odor.
After two days the shirts were placed in cardboard boxes with holes in them, and the women were asked to rank the boxes by smell using three criteria: intensity, pleasantness and sexiness.
Wedekind’s results appeared to show that the women preferred the T-shirts worn by men with different compatibility genes from theie own, raising the possibility that we unconsciously select mates who would put our offspring at some genetic advantage.
The experiment was controversial, but it did alter scientific thinking about compatibility genes.
While the mechanism behind this phenomenon is poorly understood, it has not stopped dating agencies from using MHC typing as a matchmaking tool. One lab offering such testing to online agencies (you can not smell potential partners over the internet — yet), a Swiss company called GenePartner, claims: “With genetically compatible people, we feel that rare sensation of perfect chemistry.”
As I walk to the postbox with my two test tubes of spit in an envelope, the idea of testing my genetic affinity with my wife suddenly strikes me as foolhardy. Twenty years of marriage should be the very definition of compatibility, but what if the results tell a different story? I do not want to discover that on a cold winter’s night two decades ago, my wife took one sniff of me and fell in love with my deodorant. I do not think they even make that kind any more.
Davis also tested his marital compatibility for the book and, while he may be a director of the University of Manchester’s Collaborative Centre of Inflammation Research, he admits to similar, not wholly rational, misgivings.
“It was definitely more weird than I thought,” he said, adding that his wife was “unexpectedly nervous about what they might find.”
He need not have worried — they were pronounced perfectly compatible.
They are not called your compatibility genes because they help you find a compatible partner; they are called that because they govern the acceptance and rejection of transplanted organs. That is not their intended role, either. As deputy director of research at the Anthony Nolan Histocompatibility Laboratories (where I sent my spit) Steven Marsh said: “The molecules that give you your tissue type are not there just to make transplantation difficult. Their job is to fight infection.”