Absolutely nothing about the human skeleton is ridiculously fucking easy to tell!
I'm sure we've all come across some transphobic asshole going on about "skeletal sex", or whatever the haterese lingo is today. But I've got good news for everyone: that's not a thing! Even the concept of "biological sex" at all is way more complex and amorphous than terfs want to think! I feel pretty confident guessing that the anon who sent this ask has never actually seen a real human pelvic bone in person!
Skeletons don't have two standard sizes like they were mass produced from the fuckin Gap; due to a whole bunch of complicated factors, the range of individual variance is way too wide to definitively identify, say, a skull or a pelvic bone just by looking at it. And anyone who claims they can is full of shit and not practicing good science.
Actually, when archaeologists dig up just a pile o' bones with no grave goods or any other in situ clues, they have tools that can tell them that person's age, race, place of origin, diet as a child, level of radiation exposure, how close they lived to the ocean growing up, how far they traveled, probably their last meal and possibly how they died, how long they've been buried and whether they were moved at some point, what chronic conditions they may have lived with, and even what tasks or chores they regularly did... all more easily than they can tell what that person's genitals may have looked like.
And, of course, what a person's genitals looked like obviously wouldn't tell archaeologists anything about how that person identified, because trans and gnc and intersex or twin soul people - or whatever names their societies had for them - have existed in literally every group of humans forever. In fact most ancient cultures were way cooler about the spectrum of gender expression than Americans are now; our Bronze Age Mongolian steppe sisters would be ashamed of this bullshit.
Anyway, sorry bigots: there's absolutely no science out there to back up your stupid butt phrenology cult