Ygthkb

Your not-quite-humans are amphibians, and reproduce via external fertilization in water.

This eliminates any need for males to physically penetrate females, and thus any reason to evolve a desire to do so. It also significantly restricts the environments in which sexual activity is even possible, let alone forcible.

It also reduces the impact of reproduction on female bodies, so from a strictly reproductive standpoint they need not be significantly structurally different from males. It is entirely possible that males and females could be externally physically indistinguishable (in which case, much like Terry Pratchett's dwarfs, courtship might involve a tactful process of attempting to discover just what gender all of your friends actually are...).

This doesn't mean that there would necessarily be no gender differences. Plenty of externally-fertilizing fish, for example, still have distinct gender morphs. Simply that it is no longer necessary that there be gender differences, either. Maybe the genders are distinguished by purely aesthetic characteristics, like different colorings or hair patterns--or maybe not. Maybe there are psychological differences that make one gender or the other naturally inclined towards caring for children vs. fighting and hunting... or maybe not. Just eliminate the asymmetrical impact of reproduction on one gender vs. the other, and you can have all of the equality, or keep all of the inequality, that you want.

Go digital.

Come the Technological singularity, it would becomes possible for people to exist in virtual worlds.

If people are just programs, there are no physical differences. Everybody is as strong and as fast as they want to be. The only differences are mental.

If we assume that biological males and females on your world are physically (from the perspective of strength) equal, there is still a tremendous amount of variation. Here on Earth, Japanese men and women are, on average, considerably more delicate than Samoan men and women. (Honestly, who isn't?)

My point is, from the perspective of strength (body build, muscle and bone density, etc.), the physiological differences between ethnic groups are considerably greater and more widely varied than the physiological differences between genders.

But that doesn't completely express the problem, because I've seen very tall and very short Japanese men. And don't even get me started about Sumo Wrestlers. Even the physical build within the same ethnic group can vary widely (and wildly).

And even that doesn't completely express the problem, because there are substantial differences between people depending on their health choices. Is our specimen a professional body builder? A regular exerciser? Walk every day? Eat ice cream all the time? ...

And we still haven't compared the basic differences between human biological genders.

Solution Part 1: Your planetary people is 100% homogeneous. For inexplicable and completely impossible reasons, the males (for the basic example) are on average the same physical build everywhere on your planet.

Solution Part 2: Your planetary people have an unrealistically and improbably small variation in physical build. For example: two men picked randomly from anywhere on the planet have the same height, weight, build, etc.

Solution Part 3: Your people planet-wide are very healthy, never over eat, get regular exercise, and none of them are interested in body building.

Now we get to deal with the differences between biological genders. This is easy by comparison. Almost.

Solution Part 4:

• Equal skull thicknesses


• Equal bone density


• Equal height


• Equal weight


• Equal muscle mass


• Equal muscle types


• Equal proportions (legs, arms, torso...)

Except for the hips. That's a problem unless you radically change the nature of biology. Big creatures need big babies or big eggs. Either one needs a large way of exiting the female body, which means you'll never get equal hips. We'll need to handwave this one. You could assume a much smaller egg/fetal stage such that it exits the body much smaller than human babies do or human eggs would. That's a neat trick biologically, but like I said... handwaving....

Solution Part 5 We ignore the concept of gender identity completely. Of course, having made everyone physiologically similar, it might not matter any more anyway.

And what you now have is the Star Trek: The Next Generation episode "The Outcast."

In the end, I wonder if all this effort even makes sense. I don't know of whether or not the statistics of rapes include non-alcohol, non-drug rapes where the aggressor was measurably stronger than the victim. I'm sure it's a valid point. But considering the number of rapes that include alcohol and/or drugs, I don't know if your society is really all that much better off.

Pheromones. Males are genetically engineered to require the presence of desire in females to achieve erection. In this case, physical arousal is not the same as desire, so men are just as interested in women as before, it's just that the woman has to be receptive to his advances before the plumbing starts working appropriately. And the scent of arousal is what does the trick.

Note that this will not prevent sexual assault. It is by now a cliche that rape is about power, not sex, so women will still be beaten, and presumably substitutes for the "normal" instrument will be often used. This may well result in a higher incidence of injuries above the "regular" levels common to rape, but no pregnancies will result.

Also, of course, a black market in pheromones will arise, and the really dedicated rapists will manage to get hold of the necessary to allow erection.

Make them all hermaphrodites.

You should have a look at Ursula K. Le Guin's The Left Hand of Darkness. In this story there is a new species of humans. All members of this species have both sexes. They stay androginous for 21 or 22 days at a time, then for four or five days they will manifest the characteristics of one gender.

That is regulated by a hormonal cycle. Someone in a place where one gender expression is having a majority will tend to express the other gender, as a way to balance things out. Otherwise the gender they will manifest is random.

This means everybody will experience both genders multiple times throughout their lives. In the book there was a clan that took pride in having all its members have their first sex manifestation as female, but other than that they were pretty equalitarian about gender.

Consider our close relatives the bonobos. They simply don't have the sexual dimorphism that makes human men, on average, bigger and stronger than women.

If you want a more equal society, consider making your close-to-human species more like bonobos.

Similarly, you can change family structure to reduce the importance of males wanting to raise their own biological children. (I'm thinking of an Orson Scott Card novel where men helped raise their sisters' children and it was considered rather rude to ask what man sired any given child.)

One thing to consider if you specifically rape is that the majority of sexual violence is not due to strangers overpowering their victim, but someone abusing an existing relation. A SciFi gadget is not going to do anything about that.
If you want to prevent rape in your verse, I would suggest you go about structuring society:

Give Gender Equality a few centuries

Right now this is a real world topic, plenty of famous people have been caught by #metoo. It will take time and possibly more scandals until this sinks into the base behavior of people, which may require the current generations to die out which don't have this institutionalized yet.

Monitoring Everyone

If everyone is chipped and connected to some network, everyone can be monitored. If the chip can interface with thoughts, it can monitor people, and send an alert on any possible rape, or a victim may be able to trigger the alert.
This may or may not have more dystopian consequences depending on who has access to data from these chips.

Gene Engineering

If you don't trust gender equality to work out on its own, you might engineer oneself to suppress violent impulses, and make everyone more socially compatible. This may have dystopian consequences too if the wrong people get access to this.

Neural Education

You might alternatively educate your population in proper behavior in some way that becomes instinct, and very hard for the recipient to act against to suppress rape. Again this device may have unintended consequences.

Improve laws

Even in a world where's men and women have the same strength on average there's plenty of room for variance: some men (and women) will be stronger than others. But that's besides the point, because most of the time the rape is commited by someone who knows the victim - and who already knows he can subdue her - and in the case of rape by a complete stranger they are usually armed (with knives, most of the time), while the victim is not.

So, if your main goal is preventing rape you just have to move these posts further away than we are currently trying to do:

• 
  Empower the victims, shame the rapists. Currently most of the sexual abuse, including rape, is never denounced and thus never prosecuted. Rapists benefit from this culture of silence, they know they can get away with it and it helps them rationalize that what they are doing "is not that bad".


• 
  Improve conviction ratio. It's hard to prove abuse, even rape. Contrarily to what is depicted in the movies, most rapes leave no physical traces - and counterintuitively rape by a stranger is less likely to produce injuries besides the ones the penetration has caused, if any. Many women don't fight back when raped (because it's better to be raped than to be raped and beaten up, maimed or killed). Your highly advanced civilization must have ways to prove rape, which can be much more difficult than it seems at first glance, since it's consent what tells apart rape from sex and most cases won't be "random-stalker-puts-knife-at-her-throat-makes-her-undress".

And basically, that's all. Remember that harsh punishments are no deterrent for criminals; high chances of being caught are. Since rape is a crime that always leave a witness behind (unless it's rape and murder) your only chances of getting away is either not being denounced or failing to prove the rape. Put a remedy to those two and rape will become a rarity.

A short answer. If everyone is equal in strength, you could have everyone be very dangerous. I no like you, I explode dangerous. If everyone has terrible defense and fantastic offense, rape might be less likely. Everyone could either have superpower of some sort, or a cyberpunk type weapon implanted. The cold war of rape basically. Basically the US right to bear arms on a mandatory species wide level. How effective it is to deter rapists would depend on what you give them as a weapon.

Alternatively, you could just rule sexual intercourse as difficult or enjoyable to undergo? It would normally kill off a species, but maybe humans would have some self created reason to go through with the torturous process. Enough drive to continue the species but not enough to want to rape a person maybe.

If you want to retain all other differences between males and females, simply make females bigger. This way you can still have muscle-bound men and slender women, but the difference in size can balance out the difference in muscle-mass.