David A. Holmes did not wake up one morning and say to himself, Today I’m going to come up with an equation to measure the perfect human posterior. He didn’t think to quantify backsides until a horseracing public-relations person called to ask if he could scientifically calculate what the perfect behind for a jockey would be. Holmes, a psychologist at Manchester Metropolitan University, knew it wasn’t so simple. “There’s an awful lot more to bums than you might think,” he says.
The equation that describes the quality of the female rear end, according to Holmes, is (S + C) x (B + F)/T - V, where S = Overall Shape (“including tendency to droop”), C = Circularity, B = Bounce Factor (not to be confused with “wobble”), F = Firmness (with perfect being “like a comfy bed”), T = Skin Texture and V = Vertical Ratio (the goal: “on the top-heavy side of symmetrical”). For the male rear end, the equation replaces bounce, circularity and vertical ratio with M (Muscularity), L (Leanness) and O (Overall Symmetry).
The numbers you plug in to the equation come from a list of descriptions. To calculate B for Bounce: “After one flick it wobbles for 30 secs” gives you a 2, whereas “during aerobics it doesn’t even quiver” gives you a 5. And so on. For Holmes, judging posteriors is very serious: “If I can draw attention to people’s backsides, they may actually take their overall health more seriously. Because you can dress yourself up in a suit, you can put on your makeup and cover up all of nature’s ills and pretend you’re in great shape, but if you stand naked and stare backward into the mirror, you have to confront reality.”
There’s not much debate over the perfect male behind. (Brad Pitt’s is pretty much the callipygian ideal.) But the female rear end is a different story. “There is a massive — and I mean massive — disagreement among the public between the larger, motherly, 1950s womanly bum and the impossible small, pert, athletic, rounded one,” Holmes says. He calls it “the J. Lo bum verses the Kylie bum,” after Jennifer Lopez and the singer Kylie Minogue (who scores close to the ideal). Holmes’s personal bottom line: “The J. Lo bum is more feminine and more representative of Woman; the Kylie bum is actually very close to the perfect male bum — it’s far more androgynous than people would like to admit.”
And jockeys? “They do have wonderful, strong upper thighs,” Holmes says, “but their bums tend to be sat on a lot.”
