Gov Karnstein wrote:
Tenuous similarity at best, more likely coincidence than awareness.
Depends on how you define "tenuous".
"The survivors of a nuclear holocaust from a another planet land on Earth 50,000 years ago and become our ancestors" isn't exactly what I'd call "tenuous similarity".
No, it's not even significant enough to call "tenuous." It's neither original to that novel nor a particularly obscure skiffy premise, so your point fails.
Here's another one you may not have heard: "Two people survive the nuclear war, one man and one woman. Their names: Adam and Eve."
Lather, rinse, repeat.