indus script

A lot of archeology is interpretation of evidence by the archeologist. Many of the interpretations are extrapolations. I don't know enough to say so definitively, but very often, the conclusions do not seem warranted. I try to reserve judgement since I am biased. In physics/chemistry, one takes multiple readings and checks for reproducibilty whenever possible. Obviously this is not possible in archeology and sometimes in biology and even in chemistry if the sample is tiny, as in forensics. So they have to make conclusions based on limited evidence. Since I don't understand the process, I don't know what is far fetched and what is not. To my literal mind, everything is far-fetched, but obviously I am wrong.......many archeological discoveries are acceptable.
If some object, say foodgrain is found at 100 ft in the dig, along with some other objects, by carbon dating of the carbonaceous matter, we figure out the date of that level. But consider this..... the archeologist's funding is cut, he leaves the dig and goes away. People come and go, throw their trash and go away. Soon the site is covered up either by workers or naturally. After 1000 years, another archeologist  digs it up again and concludes what? Also, now I have in my living room artefacts that I bought at great expense since they are antique. My house crumbles, and after 500 years, what do they conclude if they dig my house up?
Once human habitation has started, how do we believe levels are not mixed up by digging for building, mining or for no reason at all?
I find this more puzzling when it comes to language. The stretch of deciding which sounds in one language are similar to what in another, the use of rebus.........the extrapolations seem too large.
But nevertheless, the work done to decipher the Indus scripts is fascinating- the amount of work and the detail is amazing. I wish I could understand it better.