Scientology - Yup, no quibble with dissing that. It's a cult invented by a Sci-fi author. The name is about as close to being an -ology as it gets.
Egyptology - Funny you should mention that and contrast it to physics. Someone who first established the wave theory of light by demonstrating interference, first defined energy as a term in physics; would you say he was a physicist? Meet Thomas Young, "the last man to know everything", physicist, polymath - and Egyptologist. Actually, once a bi-lingual, tri-script inscription was found and it was realised the language had survived in the form of Coptic the study of ancient Egypt was placed on a fairly sound footing. You might wonder why anyone should bother but then I suppose a lot of people will, over the years, have wondered why anyone bothered with some of the more arcane areas of mathematics.
Palaeontology and teeth - You may have led a sheltered life and not realised this but over the years zoologists have looked at a vast array of animal species in minute detail. As a consequence they have a reasonable competence in recognising mammalian teeth when they see them. They also know - and this might come as a surprise to you - that there's an overall plan to mammalian dentition. So they can recognise what part of the jaw a tooth comes from.
They can also recognise when a tooth comes from a full-grown individual as opposed to an infant and, taking that together with their knowledge of that overall plan, they can work out that small teeth come from an animal with a small jaw (you don't get mammals having indeterminate numbers of small teeth in a large jaw). If the jaw is small it can't feed a large body so they know they're looking at a species where the adult size is small.
One of the things they also know about mammals is that they need to keep the body temperature fairly high to be active. If an animal is small it has a high surface to volume ratio so it loses heat rapidly (this is almost like a real science, say physics, isn't it). To minimise heat loss it would need some form of insulation. Given that it's a mammal this is more likely to be made out of hair rather than feathers so it's a reasonable deduction that it's a furry creature.
What else was there? Oh, yes, its diet. Again, that comes from looking at the teeth of a lot of different species and comparing them with their diets. After a while they get to recognise the adaptations that go with different sorts of diet.
Over the years zoologists have gained a lot of experience with looking at a new species and being able to predict aspects of its life-style. Such predictions can be checked. Do they have to be able to check predictions made on the basis of fossil evidence? If you're given the fact that a triangle has sides of ration 3:4:5 do you have to go through Pythagoras' theorem from scratch to know there's a right angle in there?
TL;DR Just because you don't have the background knowledge doesn't mean that nobody else does. Or, to put it another way, whatever your bag is there's a reasonable probability that it's something I don't know in detail so, on your view, if I don't know what you're talking about neither do you.