[BroJoeK]

Little Bill: "Why would anyone, in their right mind, such as they may have had in that day and age, leave readily available Wildebeest..."

Well... let me ask, do you live in the same home you were born in?
How many miles separate your current home from where you were born?
Now, based on that number of miles, how many generations would it take for your descendants to travel the whole globe?

Right.
It only takes a few miles per generation, and in time, some will reach every corner, barring a great barrier, such as an ocean.

You ask, "why would people want to move?", and the answer is: sometimes it's not a matter of "want" but of "must, no choice, move or die".
Consider any number of examples:

1. You are a second, third or fourth son in a land only "fat" enough to support the eldest.

2. A rival clan, much bigger than yours, invades your territory and you must either flee or die.

3. A drought, a flood, a storm, a forest fire, too hot, too cold, too something else forces whole peoples to leave their ancestral homes and search out greener pastures, so to speak.

4. Specifically, one theory is that humans (or pre-humans) first left Africa along the coastlines of southern Arabia, India & Asia.
   Living off the bounty of sea-shores, humans simply expanded generation by generation until they reached the far coasts of Vietnam & China.
   Once settled along a shoreline, we go back to items #1-3 above to find reasons for moving inland.

Little Bill: "I am beginning to to think that we haven't a censored clue about human origins or migrations."

No, we have many clues, literal hills filled with clues, but of course they are not conclusive in answering every question imaginable.
Still plenty we don't know.

Migration seems like a good answer to how we find certain clues in one place dated to an ancient time, say Africa a million years ago, then similar clues somewhere else at a later time.
Are there other possible explanations?
Sure, including time travel and teleportation ("beam us up, Scotty"), but so far we've found no evidence of such activities in pre-historic times.

[SunkenCiv]

Sure, including time travel and teleportation ("beam us up, Scotty"), but so far we've found no evidence of such activities in pre-historic times.

That's pretty insulting.