Looks like Venus may had habitable 3 billions years ago.
I found this on ScienceAlert.
The article indicates that it's suspected the Venus of ancient times lost it's oceans and habitability 700 million years ago. I wonder what in world did THAT to the planet. I hope hell don't happen here. The report suggests some kind gas leak came from somewhere and rock couldn't had reabsorbed the gases.
If they could have survived, i wonder if if there could have had life on the survive and fossils to be found that hadn't melted from sheer toxicity of the atmosphere.
The bulk density of Venus is
lower than the trend for our other earthlike worlds
If that was due to thermal
expansion, and if the coefficient of thermal expansion for granite / basalt on earth is appropriate, then the overall characteristic bulk temperature of Venus would be about 100-200 degrees C
hotter than earth throughout
the same calculations for Mars (slightly over dense) would imply that world was 200-300 degrees C
colder than earth throughout, which agrees with scholarly consensus to my knowledge
so Venus being 100-200 degrees hotter than earth throughout doesn't seem wildly implausible
By comparison, earth's Mantle has cooled by 200-300 degrees over the past 4 Gyr