Since our package is located outside of our bodies. If we had our legs closed it would be very painful. And since we are always on the go, we like to feel a little breeze in our junk so some guys what more breeze than others. Now your professor is either horny or drunk or both.
It's uncomfertable to sit with them crossed, to do that we need to readjust ourselves before we can even attempt that or its REALLY uncomfertable, its just not a natural position unless squishing your own balls is you're thing...
Warning: Long answer ahead (tl;dr I'd be surprised if it wasn't biological) I always see answers that point to "scrotum-squashing" or "asserting dominance as the alpha male", but I think anatomy is a more relevant source. I don't experience pain when I push my legs together, and I think pointing to subconscious conditioning is too hasty. What I did feel was my leg muscles getting too tired to justify sitting that way.
There are so many differences between male and female pelvises that it's hard to believe there is no biological differences in hip adduction (force needed to push your legs together). I found it surprisingly difficult to find scientific information on this (it might have been easier if I studied medicine and knew exactly what scientists were talking about). Looking at diagrams, I think it could be some leverage issue with the male pelvis tapering more at the leg joints so the tendons pull the legs apart. It could also just be weaker or smaller adduction muscles in men just due to different geometry, i. e. it's easier for women to pull their legs together. Like all things in science, it's probably way more complicated than I think it is. If it is biological, it could be justified by the scrotum-cooling idea. Scottish men who wear kilts are known to have higher-than-average fertility rates, probably because their testes don't overheat. So differences could be sustained by sexual selection.
Lol are you shy? Are you uneasy knowing he's letting his wang get some breathing room right in front of you even if it's concealed by clothing? I think we do it, because we honestly don't give a crap lol.
I think the point is really girl sitting with legs wide shut closed because of the societal standards about sex. I think the natural way is sitting with legs open. I've just recently met a girl who does that and I was like "f*** what?" because to me it was like an invitation to dive into her p****. But see pics of gorillas in the wild, look how they keep their legs open, and their postures in general, just like humans'. it is indeed true that the posture may sometimes be accentuated, and that's to put the d*** in the limelight, inviting for sex, or telling you they want to shag. I've done it myself
Many have of course brought up the balls things. I hate to go into detail but here it is... for a lot of guys their balls do not hang so low that they completely clear the bottom of their thighs (especially if they've got larger/more muscular thighs.) but they still sit naturally inbetween them... therefore a guy has to 're adjust' their balls to either be squashed above their thighs (Which can squeeze them into their dick... as well as being uncomfortable anyway.) or attempt to stretch them to sit below them. However even when doing this to put their legs straight it's rare for them to keep pushing UNTIL THEIR KNEES TOUCH which I will explain below.
The female pelvis is actually quite a bit wider and the angle of the hips/pelvis is stronger/larger on a women (90+ degrees as opposed to less than 70.) Because the legs on a male are both closer to together and NATURALLY sit farther outward from each other... it's actually quite difficult for a male to sit with their knees together and can cause slight discomfort on the the outsides of the hips and even middle of the pelvis (I guess it would be more akin to the feeling one gets while STRETCHING.), It may also make their lower back uncomfortable as well... in simple terms, even without balls a guy would still be uncomfortable sitting with their legs together or crossed as a women does (even without balls I think it would be difficult for a man to perform the female leg cross.)... a more flexible man however might find it much easier. The female hips are wider to facilitate child birth, the male hips are designed for optimal locomotion... the wider pelvis coupled with the angle of the hips/pelvis/legs allows a women to more easily touch her knees together.
I should point out however that sitting with your legs WIDE apart (rather than closer to 40-60 degrees.) is not necessarily optimal comfort WHEN sitting with 'good posture'... you may notice a man's leg position becomes wider AS HE SITS BACK/begins to lounge... where as a man leaning forward might have his legs closer together. So for those men lounging/leaning back with their legs widespread... they are essentially just being inconsiderate... as for your professor... don't know how to answer that as I don't know how he's sitting... I think if anything how he's looking at you would be far more telling than him sitting in a lazy position... could you imagine a man who is lounging to suddenly sit up straight and put his legs together because a guy is walking
I sit with my legs wide open. lol. That's why I don't wear dresses or skirts, well that among other reasons. It's comfortable, feels natural etc. But I also do it as a little rebelling thing towards my dad. He made me attend these f***ing etiquette classes when I was a kid, and one of the things we covered was how to sit properly. Because I'm a "lady", I have to sit properly and primly like I have a f***ing steel rod rammed up my ass and spine.
The reason why guys do it though is pretty obvious. They have a penis and testicles between their legs. Also, it is scientifically proven that the wider a males legs are apart, the more dominant his personality and the larger his penis. Because I sit with my legs wide open my friends always crack a joke that I have a one-hundred foot long penis. Impressive, eh?