We should be careful not to confuse:
- the enterprise to acquire knowledge itself
- its truths/facts, theories or models of reality
- its subject matter
If we’re talking about point 1, trivially, science, mathematics and philosophy would not exist anymore if there was no intelligent life.
Point 3 is also relatively easy to explain: Virtually nobody believes that the subject matter of astronomy (celestial bodies) would stop existing just because there is nobody around who does astronomy.
Similarly, I would say, that there are branches of philosophy (if we’re not totally misguided) which have a subject matter independent of intelligent life, like metaphysics. But this is not the case for other sub-fields, like philosophy of language.
Point 2 is the really difficult one. While simple facts, like “the Earth’s lithosphere is subdivided into tectonic plates” seem clearly independent of intelligent life, the more complex it gets the less sure I am about it. Even in physics we don’t have any absolutely pristine and flawless scientific theory. Instead only approximations; with certain quirks; where some kind of intuition is needed; where you have to take shortcuts. This doesn’t feel like the proverbial “timeless truth” but rather pretty “human”.
And this problem is incomparably worse for philosophy. So in my view, philosophical theories (well… let’s imagine we would even have one where there is some sort of consensus!) do not ‘latch onto’ reality tightly enough to be considered in any sensible way independent of humans.