Wait a minute. So you're arguing "Here's what the equivalent level PCs would be in real life in D&D, but I'm not using any of D&D's mechanics to base this on."??? If you're going to argue that a certain level of PC in D&D and what abilities they have using D&D's mechanics, it makes zero sense to not use the mechanics of the game in your comparisons. You can't have it both ways. You can't argue that a real life person would be level X in D&D based off of the mechanics of what a level X PC is, and at the same time ignore the mechanics that determine what a bear, rhino, or dinosaur have. Otherwise your argument is essentially, "I just pulled these levels out of my butt, even though the mechanics don't support it at all."
The only way you can do this is, "What sort of abilities can an exceptional person do in real life, and how does that translate into the D&D world." If that D&D PC can do much more than your exceptional person in real life (like being as tough as a dinosaur), then that means they aren't that high of a level. Pretty simple. If a level 3 PC can do everything a Navy Seal can do, and a level 8 PC can do WAY more than a SEAL can do, why would you say a level 8 is the proper comparison?