system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it that some animals have not developed particularly effective ways of protecting themselves from being attacked by another animal, despite being hunted in the same way for thousands of years?
gpt
Think about the flaw in your logic for a bit. If all deer were able to defend themselves against being eaten by wolves, the wolves would have died out of starvation a long time ago. If all deer died from being eaten by wolves, there would be no deer, and eventually no wolves.

Instead, the weakest deer, either because of poor genetics, injury, illness, or unable to recognize the threat of a wolf gets eaten. This way only the strongest, smartest deer survive. And for the wolf, the strongest, and smartest wolves survive, the weakest wolves get to only eat scraps, never mate and sometimes are driven from the pack. 

They are both in a perpetual arms race, better deer survive, and only better wolves survive. If you took a herd of current deer, and somehow magically teleported them to 50,000 years ago, these deer might be top tier creatures compared to the ones of that era.

Other animals, like krill (small ocean shrimp like things) have a different strategy, reproduce so quickly that even though they get eaten by the tons, not all of them are eaten.