Musing on the habitable zone 3.5 billion years ago

It seems to me and I am idiot that this pretty time dependent.
Mars 4 to 3.5 billion years ago could have had a much more massive
atmosphere perhaps more massive than Earth's though this would result
in lesser pressure per unit of mass. Early there is evidence
of a stronger magnetic field such take it would have stayed around.
Nonetheless, a massive atmosphere could function as a massive
blanket. A biosphere not as productive as Earth's, perhaps
only lowly organisms that tolerate a high CO2 environment.

And I'll suggest the evidence we see would come from the era
near freeze up possibly after the failure of the magnetic field.

Then there is Venus with the Sun putting out less energy
it could have been in the habitable zone. The planet could
still have its spin meaning short days and nights. It may have even
managed to have a civilization or at least complex life
forms. Then it would gradually got hotter. The seas and
ocean boil away. The magnetic field fails as the orbit slows.
The carbonate rocks finally cook yielding CO2. The nitrogen
is lost to space. So its toasted by 2 billion years ago.

Could Earth and Mars have been colonies of Venus?
Add episodic bombardments from space for their collapse and
flash to present.

just my half baked musings............Trig