While marriage itself may be a socially designed institution, the desire to be in a couple is biological. Sex and bonding are both natural rewards. Humans are part of the group of less than 5% of mammals called pair bonders. This means we have the brain structures that let us mate for life, be socially monogamous, like swans. They allow us to bond long-term, long enough for two caregivers to bring up their young. However being ‘socially monogamous’ is not the same as being ‘sexually monogamous’. The temptation to ‘play away from home’ is there in almost all mammals including humans. A good review of the literature is available here.
The reward system is the where these pair bonding structures lie. It is the same structures that drive us to the other natural rewards of food and water. Sadly, it is also where processed or artificial rewards like alcohol, nicotine, and drugs have an effect too. They hijack the pleasure/reward system. In fact, artificial rewards like cocaine and alcohol can produce an even more intense feeling of euphoria than sex. Researchers have found that pair bonders, compared to animals that are promiscuous by nature, are more susceptible to addiction. We’ll see later under The Coolidge Effect below why this is a real problem for sustaining love.
Bonding and trust are essential. We often want to express love through our body such as by hugging, kissing, caressing, entwining and having intercourse. Loving touch “soothes the savage beast” and is very healing. Couples with a harmonious loving relationship actually physically heal faster after injury. Whether we think of love in terms of romantically being ‘in love,’ or as raw passion and lust, these feelings and emotions are experienced primarily in the brain. So by learning as far as we can how the brain works will help us to experience those life-enhancing emotions in a natural way more consistently.