Because these are good questions, I'll answer some;
Physically weak
Humans are incredible long distance runners. We did a lot of hunting by "Chase it until it collapses"
9 months/15 years
Our brains take a loooooong time to mature, but it's worth it. We can plan ahead without relying on survival instincts, and we keep making amazing discoveries like fire and clothes
Great long distance walkers too. With some adaptation time, about anyone can walk about 30 km a day, for weeks. For proof, the tens of thousands of people of all fitness levels walking the Camino de Santiago de Compostela pilgrimage every year.
Proud to say I accomplished that! My dad trained a fair bit. I did like 1 10km walk the week before we started, and I finished the 800kms with no real dramas, except the first day which was a massive climb. After 5-6 days my body was totally accustomed to the task at hand.
(Super irrelevant to the post but it was an awesome experience and I would advocate anyone to undertake it, regardless of your thoughts on religion. I am not religious but did find it spiritual in a way. I did it about 6 years ago and still think about it every week.)
Started with Saint-Jean-Pied-de-Port to Roncesvalles? Yeah, it's a bit silly to start with the biggest climb of the way, but I know many people do to start from France.