 Have you ever heard the expression they had chemistry? Well, when it comes to sexual attraction, that expression is a fairly accurate way of explaining what's going on. Not in the sense of a romantic Bunsen burner lit dinner, but because of the involvement of certain biological scents. Have you ever noticed how some people smell more attractive to you than others? In this video, you'll find out why. It's been known for a long time that animals release chemical hormones called pheromones that are involved in sexual attraction. The mechanism and reasons for this attraction in humans were a mystery. That is, until 1995, when a study looked at how a man's genes, that's DNA by the way, not blue genes, could be detected by women through their sense of smell. The study focused on one gene in particular, the MHC gene, which instructs a type of immune response in the body. The scientists set out to test heterosexual women's sensitivity to male odors. The study involved volunteers, 49 women and 44 men, all of whom were selected for their variety of MHC gene types. Men were given clean t-shirts to wear for two nights and then returned to the scientists. The researchers put each t-shirt in a box equipped with a smelling hole and invited the women volunteers to come and sniff the boxes. The women had to sample the odour of seven boxes and describe it. They were asked to give each box scores for intensity, pleasantness and sexiness. Almost like speed dating for t-shirts. The results were impressive. Women preferred the sense of t-shirts worn by men with MHC genes different from their own. This all proves and brings new meaning to the term opposite to tract. It seems that we are more attracted to people who are genetically different to ourselves. This is very useful to species as more diversity in the genetics of the population increases its chance of survival and resistance to change. However, please don't give up on washing. Please like and share our videos with your friends. If you have any questions that you want help with, just comment below.