Q: I've been with my girlfriend for just over a year, and even though we've had our emotional ups and downs, our sex drives and sex lives are still fairly vital. In the past month, however, I have not been able to climax with her. Is this some kind of evolutionary mechanism that suggests, perhaps subconsciously, I don't see her as a life mate? Do males of other species "hold back" life essence from partners who aren't lifers?
A: The notion of lifelong sexual monogamy doesn't exist as an innate practice in any known species. That isn't the same as "social monogamy," in which animals pair up for a mating season and sometimes care for their young together. Social monogamy is not the norm in the animal kingdom. It mostly only exists in species that lay eggs, and even then it isn't the standard. Even social monogamy among humans has come only relatively recently in our history.
Monogamy isn't our ideal method of species propagation -- sperm selection is. Human males have large genitalia in relation to their size, and females have high sexual responsiveness during ovulation. Both are indicators of sperm competition. For an example, let's look at the bonobo. In many ways, bonobos exhibit the closest behavior to humans. They engage in missionary sex, make-up sex and French kissing. Bonobos get it on with each other constantly --males have giant testicles just so they can keep up with the demand for sperm production -- but both sexual and social monogamy are absent. Since bonobos live in matriarchal communities and are nonviolent toward each other, males don't compete over females.
Instead, they take turns having sex with them and let their sperm battle it out. That's sperm competition: Only the healthiest, strongest male will end up fertilizing the egg.
(Interestingly, the cuckolding fetish -- in which a man gets off watching his wife or girlfriend get nailed by other men -- has become more prevalent as our society becomes more open about sex. Am I suggesting you pull up a chair while the neighbors run a bonobo-esque train on your girlfriend? Yes, in the interest of science, but you're probably not going to do that for obvious reasons. I totally think it would work, though.)
I researched the crap out of your problem and the same culprit kept popping up: Internet porn. There is an entirely new field of study dedicated to the effects of it on our brains, and the results aren't good. Regular porn use numbs the brain's normal response to pleasure. When we expose it to constant sexual imagery, the brain kicks out a constant stream of dopamine, and the dopamine receptors responsible for arousal become desensitized. One result is an inability to climax during sex, an event from which a steady stream of pop shots is generally absent.
I am decidedly pro-porn, but the fact is that we consume way too much of it. Researchers actually struggle to find control groups for these porn studies -- men who don't masturbate to it regularly are all but imaginary. The good news is that it's easy to get your climax back before you head into erectile-dysfunction territory. Cut out the porn for just a couple of months and you should be back to your normal, ejaculatory self. In the unlikely event you're a non-watcher, you could have an underlying medical issue such as diabetes or high blood pressure, or be experiencing side effects from antidepressants. You could also just be over the relationship, but your question doesn't indicate that to me.