The Evolution of Love

Let me tell you about the birds and the bees. And the flowers and the trees. And a thing called love…
But hey … what is LOVE, except for the most popular topic of song lyrics?

What is Love?
The urban dictionary gives the following definition: “Love is nature’s way of tricking people into reproducing” [1]. Hm… why didn’t we just continue to be self-copying RNA as described in “The Selfish Gene” by Richard Dawkins, or simply procreate by cell division [2]? The clue is that sexual reproduction brings enormous advantages in terms of fitness: Mutations occur naturally in every organism all the time. Some may be harmful, some without impact and others may be highly beneficial. Maybe a mutation in a structural protein could give a protist sturdier ciliaries, allowing it faster movements and a great advantage in escaping predators. However, only the individual carrying the mutation will benefit from it unless it is shared. And basically, sexual reproduction is nothing else but sharing your genome with someone else. This someone will not benefit in person, but his and your offspring will. Thus sharing is caring. But does caring equal love?

Source

I'm Too Sexy...
In general, mating means higher cost for an individual at first, but pays off with increased fitness of its progeny and gene propagation. But of course, not every individual wants to mate with any other. Hence, mating strategies developed to maximize benefit. Mating strategies vary in complexity: a pretty straightforward strategy is to release attractive molecules to acquire a random partner. However, the more costly the reproduction itself, the more prudence in partner choice is advised. The decision about a partner is usually made by the female, thus males of many animal species have developed specific attributes and/or courtship behaviors that may not serve any practical purpose other than attracting a female’s attention and influencing her choice.
Birds give great examples of this: peacocks grow their beautiful and immense tails to impress females. These have no use other than to signal “I am so fit and healthy, I can afford an entirely useless, giant plumage!” (see also 'You Have Beautiful Eyes, Hundreds of Them'). Similarly, bowerbird males construct little lodges from sticks, grass, and leaves, which they even decorate with flowers, shells, and other colorful and shiny things they collect. If the lodge is impressive enough and the female decides to mate, they entirely abandon the lodge to build a nest suitable for breeding elsewhere.
Humans, too, possess attributes that serve reproductive rather than survival purposes. Compared to other primates, humans have features such as “concealed ovulation, extended female sexuality when not fertile, large visible breasts even when not lactating, large spongy boneless visible pensises relative to body size even when not sexually aroused, relative hairlessness that reveals skin quality, full lips that may mimic female genitalia by exposing skin that simulates mucosal membranes”, as discussed in detail by psychologist Lawrence Josephs [3].

You and Me, Forever
But mating alone does not yet guarantee successful procreation. A lot of further effort needs to be invested by parents to actually ensure the survival of offspring, especially in higher mammals. For humans, this can be up to twenty years! For this purpose, nature developed strategies beyond the "hit and run" approach to make mating partners cooperate until their progeny can survive on its own. Bonding mechanisms cause partners to team up and cooperate until descendants can survive independently [3,4]. This may lead to monogamy (or serial monogamy) as a favored type of relationship.
Nowadays, psychologists discuss compassion, a feeling most of us would also associate with love. Compassion also developed to ensure survival chances for vulnerable offspring because it motivates individuals to join forces and cooperate for the sake of their progeny [5]. Even early evolutionists such as Darwin considered what he called “sympathy” to be one of the strongest human instincts. While all of this totally makes sense, it does not really fit our modern-day definition of “love”.

LOVE IS THE ONLY SOCIALLY ACCEPTED FORM OF MADNESS

Maybe, it is more appropriate to talk about the psychological term “romantic love”. Psychologist James Leonard Park provides a sarcastic explanation of romantic love as a hoax or urban legend [6]. Indeed, considering archeological finds from the beginning of mankind, there is evidence for different forms of courtship behavior and for the concept of marriage, i.e. partnership between man and woman in order to maintain monogamy and raise children. Still today across the globe, people get married for practical reasons only, without any romantic consideration. Where does romance come into play then? Apparently, it is the relatively modern invention of medieval troubadours and minstrels in France [7]. Since then, European culture has spread all over the world, the newly invented concept of romantic love has entered folk psychology and is ubiquitous in songs, novels, television, and movies. Cultural imprinting, one could say.


You Drive Me Crazy
Nonetheless, most of us have experienced romantic love, and it is commonly perceived as an altered state of consciousness or “the only socially accepted form of madness” [8]. Not only because of these definitions, involving consciousness and insanity, psychologists and neurobiologists began to explore what underlies romantic feelings in the brain. Even though research has so far correlated brain regions and autonomous nervous system activity with feelings of love and identified some brain chemistry that elicits affection, science is far from answering the question: What is love?
It's good to know that instead, there are plenty of songs still to come that can tell us the answer.

[1] http://bit.ly/1fTAtUl
[2] Dawkins, "The Selfish Gene", Oxford University Press, New York, 1976
[3] Josephs, Am Acad Psychoanal Dyn Psychiatry, 2010
[4] De Boer, Neuroscience, 2012
[5] Goetz, Keltner and Simon-Thomas, Psychol Bull, 2010
[6] http://bit.ly/1mHJD9x
[7] http://bit.ly/1g2veC6
[8]http://bit.ly/1nnGFXd

by Bettina Schmerl, PhD Student AG Shoichet
This article originally appeared 2014 in CNS Volume 7, Issue 2, Neuroscience of Love