> Because vocabularies change so quickly, using them to trace how languages evolve over time can only reach back about 8,000 to 10,000 years. To study tongues from the Pleistocene, the period between 1.8 million and 10,000 years ago...
OK...there is a methodology for comparing living languages and the written record of dead languages to describe how an ancestral proto language may have worked within its family of related languages.
We can't go back much further than 5000 BC. There are no inscriptions, no surviving linguistic artifacts, no records other than cave paintings, nothing, nada, zilch from before that. There is no evidence to reconstruct a language from "the Pleistocene, the period between 1.8 million and 10,000 years ago."
No one is trying to "reconstruct a language." They are simply looking at the relationships between languages; they might be able to, within a specified margin of error; reconstruct a structure of the language based upon its descendents.