Like MSOCS, I'm with gums; however...
Although I would be considered to fall into the "natural" category, I really struggled for the first 50 hours because (as I later came to realize) of the quality of the "nurture". As a child of the Vulcan/Victor/Shackleton co-pilot instructor era in the early 80s, FJ instructors (other than creamies - that's FAIPs to you, gums) were very rare. That's not to say that all were uniformly bad, but some definitely struggled to "do" it themselves - which often had ramifications.
I was very lucky to switch at the 50-hour point to two brand-new (straight out of CFS) FJ instructors, at which point I never looked back. After 3 (count 'em) basic flying tests and a scraped pass to that point, I never again re-took any sortie, test or check-ride at any level in 4 different front-line aircraft - including the qualified weapons instructor course - over 20+ years.
But it is also worth noting, as gums identifies, that the "nature/nurture" divide reasserted itself once you'd made it onto FJs, albeit obviously at a higher level. There was the initial single-seat/two-seat aptitude/selection divide (choices notwithstanding) and then, once on the front line, there was the "squash ladder". Very quickly, everyone knew precisely where they were on that squadron ladder; and, with very few exceptions, all those at the top were in the "nature" camp. These were the actual and eventual QWIs, TPs, display pilots and Red Arrows. I generalize (some were inbound to airlines from Day One and would only contemplate CFS, for example) but you get my meaning.
At the end of my career (as a Squadron Commander) I used to get a lot of offended responses from my peers when I said that all it took to be a FJ pilot was the unthinking combination of reasonable hand-eye coordination and mental arithmetic skills. (Imagine unwinding altimeters, due to pressure error correction, while concentrating on a rock steady VSI in the turn at low-level at night during an acceleration from 350 to 600 knots all while working the radar hand-controller in gain and elevation and simultaneously calculating your bingo. Lightnings as a first tour were a real barrel of laughs, but everything afterwards was immeasurably easier for the experience). But I maintain that plenty of intelligent sporty types I knew at school would have been perfectly capable of the same - as many of their predecessors had proved during World War II and the early jet age. And, of course, they would have had to have the requisite drive and determination to succeed; but that's true for many professionals, not just military practitioners.
Yes, the newer types are more decision-driven than the older ones and, being much easier to fly, don't demand quite so much of your maths-and-motor skills. But you still have to be sufficiently ahead of the jet - in a more complex and connected environment - to operate it.
So "nature" might be the glib answer, but not - as very I nearly learned to my cost - without a good dose of "nurture".