Sorry KenV I wished to amend the post hence the deletion. My apologies.
You could watch this.
https://www.youtube.com/watch?v=aeUU9U9uY1I
Or this.
https://www.youtube.com/watch?v=aGx17P_O2LI
and possibly conclude that both nature and nurture account for IQ, and, achievement.
With regard to transgender, the experience of being in a body that does not conform with one’s perception of what one should be, has to be somewhat disturbing and difficult for that individual in society in general, but in all probability more so in the Military.
The Military has a duty to the country to try in the most cost effective way to recruit those most suitable for the purpose they are intended for, with the least disruption to it’s running. Mental stability being one quality they look for.
As a complete aside Bradley Manning has probably not been the most suitable example of transgenders in the Military.