You're talking about all this hormonal response, but how does that relate to someone you meet over an Internet connection?
HF: A lot of people think that Internet dating is unnatural, but I think it is extremely natural, because for millions of years, you might not know that cute boy over at the water hole, but your mother knows his aunt, and you know a lot about him: what he's going to grow up to become, who his relatives are, what his religion is; you know things about him. It's really much more artificial to walk into a bar where you know nothing about the person.
IK: What do you think about a generation of single people who are on SSRIs? Are they spiking their dopamine and messing with their brain chemistry?
HF: Yes. At the university I'm working with, 40 percent of incoming freshmen are on something. Ritalin for fun, androgens to build the body, SSRIs.
And you say that antidepressants not only have sexual side effects but that they dull the brain's ability to feel love?
HF: Yes, I wrote about it [with psychiatrist J. Anderson Thomson] in a chapter in the book "Evolutionary Cognitive Neuroscience."
IK: I think you're on to something, because anecdotally I meet a lot of single people on antidepressants and I would say their mating systems are very impaired. That's 40 percent of my clientele -- when one person is on an antidepressant. And I hear from lots of people whose psychiatrists or G.P.s never even mentioned the sexual side effects before prescribing.
Given the number of single mothers, could humans be heading toward a model in which women raise their babies on their own and just need insemination from the smartest, least scruffy male?
HF: I don't think so. Our brain system for attachment is so strong.
IK: On the other hand, I send my son to a school where a percentage of moms chose to be artificially inseminated or have a sperm donor. They are very successful in their careers, money is not really an issue, and they're raising their children on their own.
HF: But I would guess that if the right guy came along ... Look: One-third of all children in America are born out of wedlock; teen births are going down, but older women are choosing to have the babies on their own and then marrying the guy or marrying a different guy. But 90 percent of Americans do marry by middle age. We're just marrying later and doing more serial pair bonding.
Do you believe lifelong monogamy is possible and natural?
The word "monogamy" means a pair bond, which doesn't necessarily mean sexual fidelity. What you're asking about is a long-term pair bond including sexual fidelity. So ... sure! Forty-three percent of people are serial monogamists, but that leaves the balance of people who form a pair bond and sustain it long term.