So people make a big point of Kenyan farm boys being super fit without proper training, so that when they start training seriously they can improve faster and achieve a higher level of performance.
Could a similar thing take place in other active societies? By no means is Australia as hard to live in as rural Kenya, but Tiernan seems to have been super active throughout his life, then does a bit of volume and BOOM.
http://www.villanova.com/sports/m-xc/spec-rel/102314aac.html
He is currently only doing 70-75 mph apparently and yet has run well in cross: 9th last year and 23 minute 8km this year (though in cross times don't really matter but it was a big win). Pretty good in track too of course, with a 13:31 5k.
Of course, much like the argument for genetics based on Kenyan athletes, maybe he is just wicked talented and happened to like sports when younger. I don't mean to rehash the genetics vs. training argument as it seems obvious both play a role, and genetics is super important.
What I am saying asking is: did Tiernan doing those other sports while he was young raise his ceiling for how fast he can get, or did it simply shorten the time needed to go from not seriously training to superstar.