World Airways Evacuation From Da Nang To Saigon in 1975.
Of the 268 humans that managed to board the flight, 261 were men. There were five women and only two children.
I have a theory about survival; I believe the reaction humans have to dying is provably counter-intuitive.
The more miserable, pain-filled and disconnected humans are from Humanity the more viciously they will fight to remain alive. The more happy, fulfilled and connected they are; the more willingly humans will die to save the lives of others.
That's my theory, in any case; and if it is correct, I suspect it'd be due to the phenomenon of sunk costs. The more pain and suffering has been invested into a life, the harder the invested human will fight to survive.
Have you ever been so happy you knew you could just die right then and it'd be fine?