CAMBRIDGE, MA — It’s official: it’s not men’s fault that they think about sex all the time. Their brains really are wired that way.So concludes an August article appearing in the online version of the Nature journal.

According to Harvard molecular neuroscientist Catherine Dulac and her associates, sex drives don’t so much depend on hormones as they do brainwaves.

At issue is something called the vomeronasal organ, which helps the nose of most land animals with backbones, differentiate between various scents. In the ever-important lab mouse, the vomeronasal organ detects pheromones, which communicate important sexual and social information to other animals.

Humans and higher primates do not appear to possess a vomeronasal organ.

Of special importance to all of the other land animals with backbones and vomeronasal organs – including the lab mouse – is a gene called Trpc2. It is this gene that makes sure that signals from the vomeronasal organ make it to up the neurons and into the brain, where they can be translated.

When Dulac’s team nullified Trpc2 in their test rodents, they discovered something very interesting. Female mice with a non-functional Trpc2 gene became just as sex crazed as their male companions. The previously placid critters instead began chasing and mounting, as well as thrusting their pelvises against, making horny noises toward and sniffing the butts of any mouse that they encountered, regardless of sex.

Another set of female mice had their vomeronasal organs surgically removed, instead of genetically altered. Their experiences were similar but also included an utter disinterest in raising any young they produced. While most mother mice spend 80-percent of their time fussing over their newborns’ nest, the altered mothers grew bored after a couple of days of motherhood and wandered away. Furthermore, instead of defending their honor like normal mice, these welcomed the sexual advances of strange males.

“These results are flabbergasting,” Dulac admitted. “Nobody had imagined that a simple mutation like this could induce females to behave so thoroughly like males.”

While it’s tempting to wonder if a little Trpcs2 tweaking might not be just the thing for woman with sluggish libidos, Dulac splashes cold water on the idea by pointing out to LiveScience.com that humans don’t have the necessary vomeronasal organs, so it’s anybody’s guess what would happen. Whereas rodents are highly smell-driven, “humans and higher primates are mostly visual – hence pornography!”

While conventional wisdom has chalked sexual differences up to hormones, Dulac’s research casts doubt on that wisdom, especially given that all of the mutated mice had normal estrogen and testosterone levels, as well as fertility cycles.

Dulac opines that “While male and female bodies are strikingly different physiologically, it appears the same cannot be said for the brain.”

Indeed, Dulac believes that her team’s “research suggests a new model where exactly the same neural circuitry exists in males and females. You only have to build one brain in a species and that the one brain is built, more or less, the same in the male and the female.”