Humans and other animals get smaller with every global cataclysm...

[Mister Obvious]

[Mister Obvious]

They are trying to insist that the giant humans were around with the "regular" sized humans...

And I'd have to assert that the leftover giants were probably just survivors of the cataclysm.

[Mister Obvious]

Rather than being 'visitors' from anywhere else.

[Simurgh]

This one makes as much sense:

[Mister Obvious]

Exactly, Simurgh...

The earth started off like a seed...

Just like any other plan(e)t or lifeform...

It starts off small, expands (blooms), flourishes for its time, then starts the wilting process.