Dolphin brains

I was again reminded of the idea that dolphins might be “smarter than us” or some other such nonsense again today. I remember learning in some Psych lecture that the reason people argue for this is the brain to body size ratio of dolphins is as high as humans, but that ignores the fact that a lot of dolphin brain is needed to get them around. I agree we evolved to be a dominant species because we were able to pick up tools with our magnificent opposable thumbs but through that evolution our brains have gained a lot more high functioning sections than any other animal.
It makes me think about what I believe about animals nowadays. When I was 16, I was an atheist and I believed that that led to believing that there was no qualitative difference between humans and animals, which led to me being vegetarian. When I moved out of my parents’ house, I stopped being vegetarian, though only with a sort of unease about how every time I ate meat it was going against my beliefs. Now that I consider myself to be more agnostic than atheist, and even to err on the side of there being a substance in this world other than just the physical, this supposition seems to no longer be true. There could be something that separates us from animals. I believe there could actually be something “special” about humans, if there is some creator to the universe or some afterlife or whatever. That being said, I suppose I do think of my religious beliefs as somewhere between pantheistic and non-interventionist so there’s no reason to believe that whatever makes humans special could also apply to animals. I still like meat though.
Incidentally, did dolphins evolve in the sea? I know whales returned to the sea after being land-dwelling animals for a while and it seems logical to me that that would be true or any marine mammal.