The tendency to produce boys is entirely a question of whether a particular sperm is carrying an X or Y chromosome, the only way you get men without it is if something interferes and turns on male traits in the genertics despite having XX, which is pretty much the opposite of what you're looking for. I mean, you copuld have the fantasy world running on a different genetic basis entirely and folks just look human because the gods think that's hot, but that leaves your insert fundamentally incompatible with the locals unless he's been physically transformed (or is actually a mindstate duplicate in a new body, which is the same for your purposes but leaves the original self behind, probably mind hwammied to not rmemeber anything after saving the odd guy from getting squished.) in the transition.
Really, you're probably best off just making it a genetic disorder like the Graysons in Honor Harrington, some kind of magical equivalent like a nonhuman god angey about human birth rates making it so only one boy child will ever be born to a particular couple, or something along those lines. It also has to be something that's still active, or birth rates will essentially immediately go back to even chances.
All you really need is a standard fantasy deathworld and the biological tendency for guys to want to show off for and protect the girls; simple attrition from being the ones to jump in front of the monster first will skew your population ratio at that point, much like I figure things would work out among ninja clans in Naruto when far more ninja are male than female (2:1 on genin teams with a lower and lower ratio with age and rank) so most of the ones in the line of fire are guys while the girls have to compete or team up to get a guy who has the genetic advantages for teh next generation to maintain and hopefully improve their abilities.
Really, you're probably best off just making it a genetic disorder like the Graysons in Honor Harrington, some kind of magical equivalent like a nonhuman god angey about human birth rates making it so only one boy child will ever be born to a particular couple, or something along those lines. It also has to be something that's still active, or birth rates will essentially immediately go back to even chances.
All you really need is a standard fantasy deathworld and the biological tendency for guys to want to show off for and protect the girls; simple attrition from being the ones to jump in front of the monster first will skew your population ratio at that point, much like I figure things would work out among ninja clans in Naruto when far more ninja are male than female (2:1 on genin teams with a lower and lower ratio with age and rank) so most of the ones in the line of fire are guys while the girls have to compete or team up to get a guy who has the genetic advantages for teh next generation to maintain and hopefully improve their abilities.
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‎noli esse culus
‎noli esse culus