Let us say I have evolved.
I'll just let that one slide on past
Take away all the other variants of humanlike species and the time gap is too big.
Too big for what, are you making an argument from incredulity? Mind you, it should go without saying that you don't ignore most relevant variables just so you can argue something.
We must have evolved amongst other primates initially.
Yes and? Why are there chimps, orangutans, gorillas, neanderthals, other animals? It all came from simple single celled organisms so by the rationale you appear to be employing, given the source of all life then all life should be identical. You do realise that evolution is not solely tied to environment, it's an important part but it's not the whole story, there's mutation as well.
“Were we not strong enough or intelligent enough to compete within a similar environment?”
If we were then we would not have broken away and stayed in the trees with our cousins.
If we were not then we would not have survived, as they would have killed and eaten us.
Sorry Lateral, you don't create a limited set of options to choose from and then pretend that those options are the only possible explanation there could be.
Perhaps only one small isolated family were forced to leave the main primate groups and in doing so on arid ground didn’t want to get their knuckles burnt by having them dragging on hot sand and so they walked upright.
Ah, we're back to that 'hot ground' notion. However, as best as I understand it, it would have started small, possibly even from a small group.
Hope is but the first step upon the road to disappointment.