It slowly changes. What happens in actuality is that a rare spawn, something like an alpha raptor, will start killing off things in one of those areas, which leads to more spawns, and more rare spawns over time, and with the whole fittest survival you start to see a shift toward, “harder.” At least this is what Skrug and I ran in to on our first server. It got a bit insane after a while and we had a dino reset. But to be honest, it worked well for where we were experience wise, so after that initial reset we just left it and at that point we were killing alphas for experience.
There is a mid-game shift where you go from avoiding all that to actively seeking it once you get a decent mount or two. It changes the game quite a bit.
What drives that shift is better dinos, then breeding, then imprinting. You can start some of that with nothing but a male/female dino, a hitching post, and a fireplace. A lot of early dino eggs need heat, and you can hatch them by placing them near a lit fireplace. If you find one that needs to be colder, hatching outside works too.
Ragan and Grem have played a ton, I’m sure they can recommend more than what I know here.