[wrinkl3]

Or it could just be that there was never a lot of evolutionary pressure for the "stay fit while old" traits. Being healthy for long enough to reproduce and provide some care for your progeny was usually good enough from the evolutionary standpoint, so the frailty-at-old-age genes weren't actively selected against.

[duckduckcow]

It could be, though with a bit of Googling I found this blog post summarizing scientific studies that suggest otherwise.

https://joshmitteldorf.scienceblog.com/2016/05/16/no-animal-...