To some of us, finding the ideal mate is a one of the most crucial decisions we make in a lifetime. Many find a partner early on in life and everything appears to work out fine, but what of those of us that want to try out a few first?

Our need for a relationship with the 'right person' is fuelling a growing industry of online dating and matchmaking services. Surprisingly though, with all the gadgetry and profile matching database gobbldeygook available, a recent survey identified that out of 900 subscribers 75% hadn't found what they were looking for. This means making the right choice is as ambiguous as ever.

There are common indicators that are attractive to all of us. Most men favour a slim waist, wide hips, full lips and soft features. Women, on the other hand tend to prefer masculine facial features, strong broad shoulders, clear skin and a well-balanced physical appearance. All of which indicate virility, sexual potency and good genes.

On a subconscious level there are other factors at work. There is evidence that suggests that we could be attracted to people that possess a particular set of genes, termed as the major histocompatibility complex, or MHC for short. Partners whose MHC genes differ have an increased ability to fight off illness and disease and are likely to produce children with strong immune systems. Data proves that we are likely to make choices toward people who appeal to us in this way.

So how do you find someone who has different MHC to yours? Well, the jury is still out. However, its thought that smell has something to do with it. Some studies indicate that people are more drawn to the scent of clothing worn by those with dissimilar MHC. This is what we refer to as sexual chemistry.

However, there are a couple of caveats. Hormone contraceptives can make women favour men who's MHC genes are similar to their own. Not ideal. Male attraction can vary depending on a womans menstrual cycle. And female attraction can alter when there are changes within the cycle also.

So the point is, that the route to attraction and love can be a little like playing the lottery, particularly for women. So, when sex is factored into the equation, things can get even more confusing. After sex, the brain releases a chemical that can give the mind a warm feeling of companionship, love and creating bonds that prepare for raising a family. So having sex on impulse can give you feelings toward a person who could be totally wrong for you.

It is thought, that the purpose of love leads us to believe that we have found our one true mate amongst a choice of billions. Sex, on the other hand, takes care of reproduction, the difference between the two is clear.

Our ancestors could have believed that feelings of love would 'halt' our search for a mate and commit us to one person. We then get down to the process of mating with each other. This may be all well and good, but how do we finally settle on a decision with the right mate?

Research has found that the optimum number of choices, before whittling down the real favourites should be 9%. Out of every 100 favourites randomly met, you should study 9. Any less and you wont have processed enough information to make an acceptable choice. Any more, and the likelihood of passing the best one by will increase.

There is a chance that this research underestimates the complexity of finding an ideal partner in the real world, however the principle is clear. Dont search for too long, or you may risk missing the good possibilities and run out of time.

Clearly, who we fall for and the choices we make are subject to many different factors. We are conscious of some and not others. Opportunity can play its part too, especially if we meet someone after deciding and confirming our intentions, or at a particular stage in the hormonal cycle. Indeed, there may be someone special out there, but they may not be the only one.