There’s a pithy saying about science that goes, “All models are wrong, but some models are useful.”
“The food chain” isn’t a real thing, it’s just a conceptual model that humans use to organize and analyze information about the natural world. In actual, messy reality, all sorts of organisms eat other organisms all willy-nilly. We model that as “the food web”, because these phagic connections are all interlinked. I mean, mosquitoes which bite humans also get eaten by other creatures, which die and get eaten by detritovores, which build soil, and the nutrients absorbed by plants, which humans eat. Polar bears die and their bodies recycled the same way. That makes a web of connections.
As a conceptual model, “the food chain” is just a linear series of links in the food web. Picking out the start and the end is entirely arbitrary. Doing so can be useful in some scenarios, such as tracing PFAs up the food chain from polluted water to plankton, to small fish, to big fish, to bears and eagles and humans. In other cases, it’s not quite as useful, such as putting polar bears at the top of the food chain. I guess it’s useful, though, if it reminds you that polar bears are dangerous. But they mostly hunt seals, and only incidentally kill people, but people also hunt seals, and sometimes incidentally kill polar bears; the model gets complicated quickly.
Anyway, yes, humans can be below mosquitoes and polar bears on the food chain, if that’s how you decide to lay out a particular food chain.
There’s a pithy saying about science that goes, “All models are wrong, but some models are useful.”
It reminds me of something a sociology professor said about economic and sociological theories being lenses that focus on particular aspects of the world–they can’t see everything, but often they can narrow in on certain parts to aid our understanding.
