Gravity is a law and a theory.
The fact that it is a law is why no one doubts it.
The law of gravity tells us how gravity affects things. The theories of gravity are explanations of why gravity affects things.
Something has to be provable and falsafiable to be a scientific fact.
I believe there are aspects of evolution that are true and scientific.
Each statement has to be taken on a case by case basis.
I agree that evolution is fact.
To say that we all came from a common ancestor is much harder to prove and less scientific.
It cant be proven or disproven so it does not adhere to the scientific method.
For all I know we may have all come from one common anscestor.
But that is a statement that is speculation we can not prove it scientifically
according to the scientific method.
At least not as I read the scientific method in my biology, chemistry and science books that I have from college.