Us humans like to believe in our own enormous capabilities, our advances in the natural world. We have made it from the typical rabble of the wilderness, to king of the animals. One side of our success and our ever increasingly (so I’m told) intelligence, is that we seem to think that we have risen above the primitive impulses of the wild. Love, we say, separates us from the animals.
Now I’m not here to denounce love, because that would make me a monster and my heart wouldn’t really be in it. However, there are currently studies which suggest that even our most treasured and revered “human” characteristic, love, could be influenced by our biology. Some people might find this disturbing, or feel like it’s science trying to take all the romance out of life, however as a scientist I would argue that the search for truth doesn’t care about “romance”. Saying that, I feel that people should be less dismissive, I am as romantic as they come and yet I love the idea that it’s our biology that helps us find our true “love”. One aspect of this is that, when you know about natural processes, which are usually pulling the strings behind the scenes, you can ignore them. Learning about our primitive impulses and overcoming them, has allowed us to do things that we might never have achieved.
Anyway! Enough of this philosophic “merry go rounding”, it’s time to get on with the science. So just how do we explain Love away?
The first point that needs to be made is that this is a fairly new concept, and although there are promising studies, nothing is ever final in science. However, the concept is simple. One of the precursors for our survival, and an important one at that, is our ability to fight off infection or to resist disease. For this we enlist the help of our immune system. The immune system is a pretty big bag of tricks, but I’m going to focus on something called the major histocompatability complex (MHC).
So let’s imagine you get an infection, a virus. The common cold enters your blood stream and starts wrecking havoc. Viruses function by invading a cell, they then inject their genetic information into the nucleus. This causes the cell to start producing copies of the virus (instead of doing what it’s supposed to be doing). The result is that millions of viruses are created, the cell ruptures and these viruses are free to infect more cells.
Imagine your cells are factories, their job is to produce cars (for example), they have a blueprint of how the cars are made, they make them and export them. Now, let’s say that someone sneaks into the factory, and tinkers with the blueprints. The factory starts to produce cars with square wheels instead, but they’re following the blueprint so they don’t think it’s wrong. This is what a virus does to cells, only it gets them to produce more of itself.
While this is happening though, the cell is able to fight back. As the virus produces more copies of itself, some of the proteins it produces are broken down inside the cell. These degraded proteins (antigens) are then bound to an MHC molecule. This molecule is then expressed on the outside of the cell, so that the immune system can recognise it.
So, thinking about the factory again. While square wheeled cars are being produced, some of the workers take one of the wheels off the car, they then take it to a member of the advertising team. Who then advertise the wheel. This means that other sites, other factories see that it clearly isn’t right, and knows that something is wrong. The factory can be shut down before dozens of faulty cars are exported. The advertising personnel is the MHC molecule.
So the infected cell has this antigen sticking out the side of it, waving it around trying to tell the immune system that something is very wrong. Along comes a cytotoxic T-cell, these are the factory managers who have the ability to close the factory down. The T-cell sees that the cell is infected, and initiated cell mediated death (the cell kills itself, and stops the virus being produced).
If the MHC molecule doesn’t recognise that square wheels are wrong (or if it doesn’t have an affinity for an antigen), then they wont advertise it, meaning that the cell wont think there’s anything wrong at all. This is a simple way of explaining how the MHC molecule plays a role in immunity, there are actually dozens of roles for MHC molecules, this is just one of them.
Believe it or not, but this is where love comes into it. You see, from an evolutionary point of view it is important for us to create offspring that will be fit and healthy, and will live long and have lots of children. So we obviously want to produce children with healthy immune systems, one of the best ways to do this is to give them a huge variety in HMC molecules (the more variation they have the more likely they will present antigens to the T-cells). The best way to get variety is to reproduce with someone who has different genetics to you. Diversity is always a good thing when it comes to genetics (which is why inbreeding is so unhealthy). To explain this easier take blood groups;
If you have two parents who have the blood group O, they will only have children with the blood group O. However if you take one person who is A and one who is B, the children can have O, A, B or AB blood. So genetically different parents produce a wider variety of outcomes for the children.
This is the same for MHC molecules, let’s say Jess has MHC molecules that recognise chicken pox, influenza and measles. However Jess doesn’t have MHC molecules that recognise small pox or yellow fever. If she has a baby with Jim who has similar MHC molecules, their children will still be weak against small pox or yellow fever. However, if Jess has a baby with Rob, who has MHC molecules that recognise small pox and yellow fever, their children are more likely to have a better immunity against all the viruses. It really is that simple (well….no it’s not, but in a nutshell!).
The point of MHC molecules and love is that, MHC molecules have been shown to affect the olfactory system (sense of smell) although it is unknown exactly how. There was a study conducted by Wedekind et al (see sources) where girls at a university were asked to smell different t-shirts belonging to men. The men had worn the t-shirts for two days without deodorant or fragrant soaps. The girls were then asked to rate the T-shirts. The girls typically scored men with different MHC genetics higher than those who were similar. The effect was then reversed if the women were on an oral contraceptive.
So next time you’re talking to someone and feel like you’re drawn to them, like they’re “the one” it could be their genetics talking. It would also help to explain when you meet someone who is everything you like, and looks fine but just doesn’t do it for you. The level of pull this has in finding a partner is always going to be debatable, but it does give a different spin on the idea that love is something we cannot explain. It might also help to explain how we sometimes just find ourselves drawn to someone, without knowing why.
So remember, don’t judge a book by it’s cover, judge it by it’s histocombatability complex!