Romantic Evolution

Let’s go back 3.5 million years ago, right around when we started to walk upright. Travel on two feet had plenty of advantages, but for mothers, it presented new challenges. Now, they were forced to shuttle their progeny around on their backs or in their arms.

With hands full of child, there was far less room for berries, roots, and spoils of the hunt, and running from predators wasn’t such a snap. They needed help. They needed a partner.

The first serial monogamists

Partnering led to a primitive form of romantic love called serial monogamy, in which pairs stayed together for a period of time before moving on to form a couple with someone else. Scientists believe our ancestors only stayed together long enough to rear a child through infancy, which was around four years. After that, they’d go their separate ways, form new couples, and increase and differentiate the population.

That lovin’ feelin’

The thing about raising children together is that it forms bonds, so our ancestral pairs may have started forming attachments to one another. Though some would’ve split to multiply their contributions to the gene pool, for others, feelings of attachment kept them together for longer and impelled them to have more children. While the primitive brains of these ancestors make it unlikely that they experienced love in the way that we do today, the long-term attachment probably formed the root of today’s romantic love.

And now, sweet talk

Then came language. About 1.8 million years ago, we pulled together the capability to express ourselves with words. It might be argued that there’s no better way to express romantic affections than through words, and it’s likely that when language appeared, early humans’ capacity for expressions of love exploded. Now they could woo, tease, and flatter one another with stories and gossip and song — things that can only really be done with language. Realtalk: ladies love a good sonnet.

Quick — through the stomach!

The brain growth that facilitated manipulation of language was partly due to our discovering cooking. By learning to cook food, early humans increased their caloric intake, which spurred the development of big, hungry brains. One of the areas of the brain that increased in size was the caudate nucleus, an area associated with the motivation to seek and win rewards. This led to increased efforts in trying to attract an appropriate mate — and is probably why some people will do anything to be with their loved one. The adage that the way to a man’s heart is through the stomach might actually have some distant truth.

But larger brains meant larger skulls, which meant more problems during childbirth. In order for babies to fit through the birth canal, children had to be born before their brains and skulls were fully formed. Because they were born less developed, it took more time before they were able to fend for themselves. This forced couples to stay together for longer periods of time, and thereby strengthened feelings of romantic love.