I'm going to say something pretty controversial but that I very much believe in - body phenotypes change based on genetic activation. If you start training as a distance runner when you're young (i.e., early stages of puberty), you will not proceed to grow into some massive beast meant for football/basketball. You might be extremely tall, but not incapable as a distance runner.
The longer I live life, the more convinced I am that our decisions do indeed impact which genes we express. If this were not the case, we would see massive hulking individuals helpless about their body composition but still passionate about marathon running from a mental standpoint. Instead, we see that everyone who is truly passionate about running from an early age is lean and toned, not a massive tank lumbering along.