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My question is very specific. If the Earth had evolved to never have animals, and instead only have plants and fungi, could the Earth be habitable for humans, or any life at all? Could it be breathable for us? And could the plants and fungi evolve to the point where they can move on their own, have brains, and even eat?

I thought of this idea one night when I was thinking of alternate realities, and wondered if this was possible. Please, I need to know if this is even somewhat plausible. To be even more specific, the plants would still do photosynthesis, as we know they do, but the fungi would have to eat like us. Is this possible or even plausible?

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  • $\begingroup$ "or any life at all"... wot, you don't think your plants are life? $\endgroup$
    – PcMan
    May 9 at 15:45
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    $\begingroup$ I don't really think this question is a duplicate. There's a great difference between suddenly removing the animals from a planet, in which said animals have already developed special relationships with other organisms and thus were important for the maintenance of portions of various ecosystems, and having a planet in which they didn't exist to begin with, which means those special relationships that would result in impacts to the environment should the animals disappear were never formed to begin with. $\endgroup$ May 9 at 16:24
  • $\begingroup$ The differences between 'animals' that evolved from plants and fungi vs animals that evolved directly from unicellular life would be largely semantic. The demands of motility will create organisms that handle energy and consumption in much the same way, regardless of origins. The functional structures involved will look different, but function similarly. $\endgroup$
    – DWKraus
    May 9 at 17:19