"It" being a biological basis for romantic behavior? We've survived this long without know how, or if, biology determines our current romantic behavior, I think we'll be okay. We're not going to go extinct because everyone is fucking robots.
Humans have existed a lot longer than science or the contemplation of nature vs. nurture.
> no evidence of the opposite
There's plenty of evidence that romantic behavior is culturally determined. Just look at how much it has changed over the centuries even though, biologically, humans have hardly changed at all. There's also the wide variance between cultures geographically in which we're all biologically the same.
"It" being a biological basis for romantic behavior? We've survived this long without know how, or if, biology determines our current romantic behavior, I think we'll be okay. We're not going to go extinct because everyone is fucking robots.