This episode of Sexplanations is sponsored by Adam & Eve dot com, where you can find so many sex toys to masturbate with.

[whip cracking sound, throat clearing sound]

The other day I was washing my crotch and did one of these rubbing gestures on my clitoral hood. My intention was to move the running water through the folds and clean things out, but doesn't it resemble something else? Like masturbation?

It got me thinking. Maybe hygiene is the reason we masturbate. So I present to you my hypothesis and a handful of others actual evolutionary biologists have studied. Just to note that the names of these hypotheses aren't official, they're just my way of organizing them.

The Horny Hygiene Hypothesis: masturbation is correlated with moving cervical fluid through the reproductive system, helping clear out bacteria, other pathogens and irritants. But I propose it can do even more. Imagine that my head is erectile tissue, like a clit or a penis, and my hood is the foreskin. Around puberty, this area is kept soft and lubricated by a substance called sebum.

Sebum is great, but if it's left there for a few days, it collects dead skin cells, and bacteria, and all of this together becomes smegma, represented here by tissues. It's an odorous buildup that looks like cottage cheese, and it tends to cause the head to stick to the foreskin so things don't move around nicely anymore. If only there was a way to simply clean this out! Like inheriting a sense of pleasure from touching myself, which in turn retracts the foreskin, dislodges the smegma, and makes my body more hygienic, so I'm less likely to die and more likely to pass the horny hy-gene onto my offspring.

What do you think? Is jostling your junk for hygiene an evolutionary explanation of masturbation? What about this one? The By-Product Hypothesis: basically the idea is that pleasurable sex reinforces reproduction and pair-bonding, so stimulating your body in a similar fashion has a similar effect. Sounds reasonable. Makes me love that I have flexible digits at the end of these conveniently long appendages so that I can mimic reproductive efforts. And that Adam & Eve dot com sells sex toys that do the same thing.

Next: the Iguana Hypothesis. In competitive mating systems, where males fight over females, masturbation might work as a release for those males who can't get laid, or as a way for them to get laid but not die trying. An example of this is male marine iguanas that keep harems of females. They're really aggressive toward any outside males who want in on the action. So to reproduce, harem-less males will rub against rocks until they're close to cumming, then they'll mount a female all quick-like, inseminate her, then flee for safety.

Is this why we masturbate, or is it the Bored or Broken Hypothesis? Take for example birds in captivity or your family dog. Observations of them humping playthings suggest that they might have incorrectly or inappropriately adjusted to their environments, leading to maladaptive behavior, in this case masturbating. That, or they're adapting effectively to cope with boredom, anxiety, sexual tension, et cetera.

The Old Sperm Hypothesis: the thinking here is that sperm are more viable the fresher they are, so by masturbating, old expired sperm are flushed out and the new athletic sperm can line up for sex that's procreative. There is some validity to this, but it really depends on how often masturbation happens.

The Vestigial Hypothesis: vestigial refers to body parts, traits, or behaviors that served our ancestral species but don't have clear functions now. For example, tail bones and goosebumps: tailbones for tails we no longer have, and goosebumps to stand hair on its end so we could look bigger in threatening situations. Now we have different body hair, which isn't going to do this, yet we still experience goosebumps. Similarly, masturbation could have played a more prominent ovations role in the past. Its origin may have more to do with how it served a species we evolved from than how it serves us now.

The Learned Touch Hypothesis: I really like this one. This hypothesis proposes that masturbation evolved for a better understanding of anatomy and physiology. If I explore my body through touch, I'll figure out what feels good, I'll be more likely to orgasm, and sometimes during orgasm other physiological things will happen that increase fertility, like my cervix dipping down into my vagina repeatedly so it's easier for sperm that could be pooled there to access an egg.

This relates to what I call the Exhibit Hypothesis. If getting off through masturbation is something I display, like, "Look at me cum! Look at me cum!" then masturbation might have evolved to teach potential partners the techniques that please me. Or tempt them into wanting in on the sexytimes I'm having.

I think my favorite is the Panacea Hypothesis. Panacea refers to a universal remedy, a cure-all for every problem, and today, I propose that's masturbation. Certainly not for everyone or all things, but masturbation is known to:

• boost the immune system
• decrease cancer risk
• elevate mood
• enhance skin complexion
• heighten senses
• improve sleep
• increase blood flow
• lessen cramps
• lower blood pressure
• minimize incontinence
• reduce stress
• release tension
• relieve pain, and
• slow signs of aging

Not to mention, it can feel amazing. What if masturbation evolved as a built-in way for us to self-care and self-soothe, like a handy mechanism for us to cope with the crisis of living?

Whatever the reason is, I'm certainly thankful for it, and I have a lot of curiosity about how masturbation will continue to evolve. Please share in the comments any ideas you have about masturbation's evolution and stay curious!

A special thanks to evolutionary biologist Sally LePage for her review of this episode, and to Tom Price, who is studying the evolution of masturbating in birds. There are links to their work in the description, as well as an incredible deal from our sponsor, Adam & Eve dot com. When you use the discount code DOE at checkout, adamandeve.com will give you fifty percent off an eligible item and free shipping on orders sent to the US or Canada.

[outro music]