Good on you for pursuing new facets of your physical abilities!
Cellar Yeti wrote:
Humans are perfectly designed for power, speed, endurance, and strength
By "designed" I assume you meant to say "evolved"
I would even argue that humans are for better evolved for endurance than for speed and strength. A cheetah can run 75 mph, a beetle can walk around carrying 850 times its bodyweight, both of which make humans look absolutely pathetic in comparison. But over a long enough distance, humans can outrun nearly every land animal on the planet. This, along with our ability to reason, is our great trademark genetic advantage on this earth. Daniel Lieberman at Harvard has been doing extensive research on this very issue.
That said, 100 miles is an awesome goal, and should be treated with the awe and respect it deserves. Do not skip steps. I like that you seem willing to let it take however much time it needs, rather than setting an artificial deadline to accomplish it by. Good luck!
I have not yet pushed beyond the marathon distance, but I may in the future.