I think far too many assumptions are made about habitability. Humans exist in a fairly narrow band of habitable conditions but some life could be very tolerant.
Its entirely possible that life could exist on the earth if it were as close to the sun as venus or as distant as mars. It wouldn’t be exactly the same as us.
There are innumerable variables that could be taken into account and virtually all of them are possible. Maybe a planet orbits a star in a cluster where the other stars provide enough cumulative heat for earth similar life.
The general rule of thumb is that life needs liquid water.. within that range, life has been found in Arctic areas and volcanic vents. Intelligent life (tool users) would require a more precise environment. A water world would likely prevent life from using fire, a key ingredient to advancing a society. Material for easily fashioning primitive tools is another. Imagine if plant life was only grass and moss. You couldn’t make a crude spear or axe.
That’s a good point, often missed by many. Extrapolation is pretty difficult when you are going off an example of one.
Freegards
Thanks, and I agree — but also, conditions on Earth have changed, rapidly, so many times, that the foolish idea that everything has been uniformly and barely changing is egregiously in error.