Amir Levine in The Washington Post:
For humans, biologically speaking, soul mates are entirely real. But just like all relationships, soul mates can be complicated. Of course, there isn’t a scientifically agreed-upon definition for “soul mate.” But humans are in a small club in the animal kingdom that can form long-term relationships. I’m not talking about sexual monogamy. Humans evolved with the neurocircuitry to see another person as special. We have the capacity to single someone out from the crowd, elevate them above all others and then spend decades with them.
In other words, soul mates are made possible for us because of the way our brain is wired. What’s fascinating to me is that we are all unique. Our DNA is unique. Our faces are unique. Our brains are unique. And yet we all have the brain neurocircuitry to see another person as more special than anyone else. What happens when we make someone special like that is they become more valuable than others. There’s a lot more at stake whether they call us or don’t call us.