Do you think ability to work super hard is somewhat genetic?

So recruiting into MBB you already pre-select into a cohort of ~ top 10% people in terms of work-ethic, career ambitions/drive. Just pick out the 5-10 most diligent / hard-working individuals of any University cohort to see what type on average ends up working at a MBB.

Now among these preselected group of already super hard working individual a new normal-curve establishes itself within the MBB.

What I observed is that there are professionals who clock in insane hours with an relentless drive and a zero complain attitude. I saw APs/principals who sat shoulder to shoulder in team-rooms until 02:00 AM just top open up a new deck for a client-pitch/discussion on the next morning that they edited until 03:00 AM ... (and later got up at 06:00 AM to catch the first plane to the client). And these are not single instances but fair representations of their working schedule.

I'm really wondering. Do you think this is all just pure grit/dedication or are there genetic forces at play that make people tolerate insane hours with more ease? I personally can't stomach working past midnights for too long.

This is a question that has swirrled around my head for some time so I would be interested what the community thinks :D