Venus, What was it like in the past?
All that we know about the past of Venus is that it is slightly smaller than earth, being about 95% of the mass, 72% of the distance from the sun, with an atmosphere that is about 100 times that of earth, mostly composed of carbon dioxide, and highly volcanic. Apart from this virtually all evidence is 99% confirmation biased guesses. It is not a twin of the earth, and it’s likely that it never was and never will be, the parameters that produced the earth being only fulfilled in about 1% of cases. Will the earth go this way, probably no chance. It would need to fulfil about 99% of conditions it hasn’t presently got. An example, humans have an average mass of about 136lbs, so a 95% difference would be about 129-143lbs. Therefore the assumption that everything that weighs between 129 and 143 is a twin, a small horse, a dolphin, a small tree, a pile of bricks, and started out the same as a baby, but due to environment went different ways. Similarly, Mars, which is closer to the moon in environment than the earth, whatever people say. It has an atmosphere 1/100th that of the earth and is much smaller and farther away from the sun.
Similar conditions produce similar things, but this is only based on observations in a privileged environment. True a number of constants are there, but in fact, most of them are approximations based on an earthly environment, and need a lot of conversions and adjustments for anywhere else, structures created using these components not usually being experienced by experimenters here. Mountains grow differently, crystals and minerals grow differently, and things found here not being able to exist elsewhere, and things found elsewhere not being able to exist on earth.
One thing is apparent, we need to stop being purely terrestrialist in our thinking about other places, even exobiologists and exogeologists constantly using earthly comparisons for the basis of their opinions, where there is no evidence that they are true in another environment.
Venus and Mars are not Earth, and Earth is not Venus or Mars, so only the loosest and uncertain of comparisons can be made.