(“Recently”: during the Classical period in Europe)
This isn’t a meta-post; I’m linking to a ling.se answer because it’s the only place I know of where this idea is expressed: Why did early Indo-European languages seem to be morphologically complex?
The author, despite being clearly outside of the academic mainstream (and having a somewhat confrontational tone), appears to have thoughtfully and intelligently argued his point; i.e., he is not a crank.
I’m curious to what extent this idea is plausible scientifically, what evidence there is for or against, and to what extent it is current among “serious” theoreticians.