Nicholas Christakis ’84 is certainly not the first person to come to Yale for networking. Christakis is a professor of social and natural science and co-director of the Institute for Network Science at Yale, which will hold a grand opening tomorrow. His work has shed light on how some phenomena, such as obesity, divorce, and happiness, can spread through our social networks, and how others, including sexual orientation, cannot. Christakis sat down with the News to discuss relationships, sex, and the evolutionary logic of Freshman Screw.

Q. Why do you study networks?

A. If you think about it, a dyad — a couple — is the simplest type of graph in a social network. It’s two nodes with a tie between them. But humans are actually in networks and graphs of much greater complexity — you have your friends, partner or partners, your siblings, and each of those individuals in turn have similar [connections]. We assemble ourselves in a very ornate pattern. And we proceed to live out our lives in a particular location in this graph — this network. And where we are in the network has implications for all sorts of things.

One of the deep ironies about human beings is that when we are free to do whatever we want, we often choose to copy our neighbors. We engage in a kind of social learning and social mimicry all the time. Humans have evolved, we believe, to not just have dyadic relationships, but to have complex social network relationships.

Q. Is forming social networks an innately human tendency?

A. Yes. When you go out and you map these social networks, they have very specific topologies and architectures — you see that everywhere. We’ve done some work that suggests that the structure of human networks is very heritable — sort of rooted in our genes. So if that’s true, if we could go back 10,000 years to the Pleistocene and look at humans beings then, we would expect them to have social networks very much like ours. We can’t do that, but the next best thing we can do is look at the social networks of people who live like we did 10,000 years ago, like the Hadza hunter-gatherers in Tanzania, so we did that. We, in collaboration with some anthropologists, mapped the social networks of the Hadza. We created a Hadza Facebook — a photographic census of the population. Despite the fact that we have invented agriculture, cities, and telephony, the network structure the Hadza make are indistinguishable from those of Yale students.

Q. Do you see patterns in social networks like Facebook that resemble the networks humans actually form?

A.Yes — they have a vaster scale, but certain summary statistics that quantify the networks are the same. For example, there is something known as transitivity, which is the probability that two friends of yours are friends with each other. The Hadza have about the same transitivity as Facebook.

Q. Your work in the past has dealt with how sexual behavior is affected by our social networks. Could you elaborate?

A. If your friends start having sex, it affects the probability that you’ll start having sex. But sexual orientation doesn’t spread, and that [aligns] with current thinking on the origins of homosexuality.

Q. How else can networks influence our relationships?

A. People think they can form their own opinions about partner suitability. It turns out that there is actually a much better predictor, something known as “surrogation.” If I were asking you to evaluate how enjoyable it was to drive a specific model of car, I could describe the linear feet of legroom, 0-60 acceleration, and the feel of the car, and so forth. Or I could just tell you, “This guy here — he really likes driving this car more than this car.” It turns out that latter way of giving you information is a much better predictor of your own enjoyment. So people are bad judges of what they’re going to like. Your friends are actually really good sources of information as to who the best partners are.

Q. Do you think the perspective of your friends might be part of what is driving the omnipresence of social networks across all cultures and time periods?

A. Absolutely! There’s also some other work that describes that people are more likely to have sex with people that they were introduced to by their friends than people they were introduced to by their parents, which kind of makes sense. But the basic point is that the network is an excellent source of introductions, whether you’re just looking for sex or a long-term relationship. And one of the ways to use your network is to branch out. I often suggest to people that engaging in activities with a diverse set people puts you in a position to meet people. So, you know, go to an entryway party in a different college.

Q.It sounds like you just scientifically justified this weekend’s Freshman Screw. What do you think of Yale’s screws?

A. I think that’s great. Your roommates pick a blind date at some social distance. There’s the disinhibition that comes with the institutionalization of that, so I think it would be very effective. It would be wonderful for someone to do a study evaluating success — how many lead to a sexual relationship, how many lead to a long-term relationship.

Correction: Feb. 4

A previous version of this article incorrectly named the organization Nicholas Christakis is the director of as the Center for Network Science. It should have said the Institute for Network Science.