It’s a universal human phenomenon, but scientists have long struggled to pin down the biological foundations of love.
Now, in a new study, a research team has found evidence that humans evolved to fall in love.
Earlier research has attempted to find a genetic or neurological basis, but the new research presents the first evidence that love influences reproductive success, as measured by the number of children people have.
The research showed that commitment to a partner in both men and women was associated with number of children in the hunter-gatherer Hadza people of Tanzania.
The research “may shed new light on the meaning of love in humans’ evolutionary past”, the authors wrote in the study, published in Frontiers in Psychology.
In modern Western societies, factors such as contraception disrupt the potential link between love and number of children. That’s why the research team, led by Dr Piotr Sorokowski at the University of Wroclaw, chose to study the Hadza.
They reasoned that the Hadza lifestyle is more comparable to that of our prehistoric ancestors, and could therefore provide insights into the early evolution of love.
To gauge the love felt by the married individuals who participated in the study, the researchers used a method called the triangular love scale.
The scale is based on three components that as a whole are meant to measure the depth of love: Intimacy, passion and commitment.
After gathering responses to score each participant for those three components, the scientists compared these scores with the number of children born in their current marriages.
“We found that commitment and reproductive success were positively and consistently related in both sexes,” the scientists wrote.
They also found a positive association between passion and reproductive success in women.
A negative correlation between intimacy and number of children, on the other hand, could result from a dip in intimacy between partners when there are lots of children around.
The scientists suggest that passion and commitment, therefore, may be key factors that increase the possibility of reproduction. This would mean that “selection promoted love in human evolution”, they wrote.
“I really like what this team has done,” said Professor Michael Gratzke, a linguist and founder of the Love Research Network at the University of Hull, noting that it’s also important to be aware of this study’s limitations.
The concept of love varies between cultures, he says, and this should affect how the results are viewed.
“I don’t know if any concept of love exists in the Hadza language, and I don’t know how that would have been conveyed,” he said.
Furthermore, he notes that in much of the world, love is not necessarily viewed as relating to reproductive success.
“The other question is what does this mean for people now?” asked Professor Gratzke.
“We are not hunter-gatherers by and large, so the way we organise ourselves in relationships obviously may be very different.”