When Theodore Roosevelt was a young adult, he was told by his doctors that because of his many serious chronic diseases, he should take up a soft indoor occupation if he wished a normal lifespan.
Instead, Teddy self-consciously took up his famous 'vigorous life'.
(However, partly due to his excessive vigour, he in the end only lived to age sixty, which he might also have reached if he had taken up the soft life !)
He lived in an age when most scientists considered that humans had a very, very, limited ability to alter the health their genome gave them at birth ------ except to drive it downhill and then inevitably pass that bad health on to their descendants.
As such, he should have been written off from childhood as defective, degenerative, unfit, 4F.
If he was born poor, black or foreign, he probably would have been --- but he was born instead into one of the most famous of old families and wanted for little all his life - good health aside.
So Teddy got to display the incredible plasticity that lifeforms are truly capable of, when driven hard enough by sheer need and strong will.
Roosevelt was the US president during the formative years of Canadian-born Martin Henry Dawson and I often wonder whether his very well known story influenced Dawson's contrary attitude to his chronically ill charges written off by most of the world.
My 'wonder' matters because however it was formed, the dying Dr Dawson's unwillingness to let other chronically ill die by government benign neglect during WWII kickstarted the systemic use of naturally-made penicillin and thus made life better for ten billion of us (and counting) ever since October 1940....