See that line across the road just about in the middle of the photo to the left? That's an ant trail. It was there when I was a little girl visiting my grandparents. It was there when my mother was a little girl and my grandmother told me it was there when she was a little girl and her mother told her it was there when she was a little girl. So that ant trail has been in the same spot for more than a century and a quarter, and very probably a lot longer than that.
How much longer? Who can say, but probably a lot longer than that road has existed, centuries maybe, maybe thousands of years. Maybe it was there before the Indians came. If I learned that it had been there since the glaciers retreated 11,000 years ago, I wouldn't be surprised. And if, somehow, I was to learn that that ant trail would still be there when the glaciers come grinding down from the north again, as by and by they surely will, whether that's a hundred years from now or 10,000, I wouldn't be surprised, either. What is time to an ant colony anyway? We humans are like mayflies compared to colonial creatures, whether ants and termites or coral polyps.
Then there are plants. Some years ago I came across a study of the flora of the Mojave Desert. It mentioned that the author had found a creosote bush that was 12,000 years old. The plant grows by spreading out in an ever-widening circle. Underground the roots spread from the central, original plant, the above-surface parts of which may die, but beneath the surface, it lives on, essentially indefinitely. Even a fire, which may burn off the above-ground parts of it, won't kill it because the root structure is untouched. It can, of course, be killed. In this case, the bush was bulldozed into oblivion to make way for a housing development. Alive since the beginning of the Holocene, a grassland ape destroyed it to create another one of its ever-proliferating nest heaps.
Do plants think, are they sentient? Define sentience. Is there only one type? Is your definition valid for any life form other than hominids? How do you know?
How about fungi? I once listened to a very -- very -- smart guy proposing and defending convincingly the hypothesis that all fungi on the planet are really just one life form that has been continuously alive since the first fungi evolved. What about the oceans separating continents, and continents moving around via plate tectonics. He had an answer to that, but I forget what it was.
Fungi and vascular plants interact intimately with each other. Fungi act as a communications pathway between trees, conveying information about their health, telling a tree that it is time to die -- yes! that's true -- among many other things including, no doubt, things we, as animals, could never understand, or even be aware of.
Are fungi sentient? How about the combined symbiotic creature that is a forest/fungi symbiote?
I recall reading, maybe in The Soul of the White Ant by Eugene Marais, speculation about social insects having a group mind, rather like that of the Borg in Star Trek: The Next Generation. I watched that with my dad when I was a kid and remember him saying, "Borg, Borg, okay Borg. But where's Warner, that's what I want to know. What did Borg do with Warner?" I had no idea what he was talking about but my brothers laughed.
I digress. Where was I? Hmm. I forget.
“If a lion could speak, we could not understand him.”
―Ludwig Wittgenstein, Philosophical Investigations