An interesting fact that I learned from the book Metazoa is that biological diversity was greater in the seas than on land, until about 130 million years ago, and then the explosion of diversity on land, at that time and still now, was because of a feedback loop that developed between plants and insects, with the insects allowing greater specialization among the plants, and the greater diversity among plants allowing greater diversity among insects. This was a true feedback loop, in that it would be impossible to say what the starting point was, the insects or the plants.

https://www.amazon.com/Metazoa-Animal-Minds-Birth-Consciousn...

Peter Godfrey Smith covers some of this in his book Metazoa but he rejects pan-psychicism and tries to make us believe that pure materialism can explain consciousness, as it emerged in animals over the last 750 million years, going back to an unknown ur-brain that might have existed in the first bilaterian:

https://www.amazon.com/Metazoa-Animal-Minds-Birth-Consciousn...

However, I was not convinced by the material argument, which seems just as magical as any other explanation, as there comes a moment when we have to believe “then something magic happens and the creatures suddenly have real awareness of their surroundings.” Having read the book, which denounced pan-psychism, I actually found myself more favorably inclined to pan-psychism , since it clearly is no more magical then any other explanation.