Our Sexual Determination

Some quick facts about species and their sexual nature.

In humans (and many other species, including dolphins--who don't have a sense of smell--mice, etc.) we have pairs of nerves lined from front to back along each side of our brain. They label these as Nerve 1, Nerve 2, Nerve 3, and so on (1 being at front to 12 at the back). The closer the nerves are to the front of the brain, the more important they are to the entity. Nerve 1 is the front nerve (or was thought to be), which controls the sense of smell. Recently researchers have discovered a new nerve, even more toward the front--and thus, more important--than Nerve 1; they named it Nerve 0. This nerve is believed to control sexual attraction. Here are some interesting facts about Nerve Zero.


• Nerve 0 is suspected to be a sexual attraction sensing nerve
• Whales and dolphins have it, but do not have a sense of smell, which scientists thought Nerve 0 was directly related to. Indicating that it doesn’t aid in the sense of smelling.
• Nerve 0 is the very front nerve in the brain; even closer to the front of the brain than Nerve 1, which provides the sense of smell. (both nerves connect to the nasal passage)
• Female hamsters, when given the scent of a male’s urine after mating with a different male, could not get pregnant as a result. The pregnancy was literally aborted. If given the scent of the same male, it had no effect.
• Human brains contain 6 of the same pheromone receptors present in mice, which send sexual attraction signals through the nose.
• When severing Nerve 0 in hamsters to see if they could still find a hidden cookie as well as other hamsters that hadn’t had the Nerve severed, they could find it just as quickly; however, they failed to mate.
• On the way to the brain, some fibers in Nerve 0 took unexpected side trips and sent branches to the retinas of the eyes. Nerve 1 doesn’t take this route; this shows a difference between the two. When scientists stimulated only Nerve 0 on goldfish by sending a mild shock which didn’t stimulate Nerve 1, the male goldfish responded instantly by releasing sperm.
• Nerve 0 connects the nose to parts of the brain controlling sexual reproduction.

For details on this, read the April 2007 issue of Scientific American Mind Magazine