A startup Massachusetts dating service has the usual questionnaires about likes and dislikes, but bases compatibility specifically on how one person smells to another (straights and gays accommodated). Eric Holzle’s ScientificMatch.com tests each person’s “major histocompatibility complex” (MHC) genes, the science behind which dictates how one person will translate the scent of another (with similar-processing people less compatible). (In one famous study, women preferred the smell of T-shirts from men whose MHC was the most different from their own.) Holzle predicts a higher success rate than for ordinary dating agencies, but at a fee of $1,995 per client.