[canjobear]

The idea that recursion was the key mutation that led to language is not doing so well lately. It turns out that non-human animals already can produce sequences with recursive structure [1]. It's also not clear that all languages have nested recursive structures.

[1] https://advances.sciencemag.org/content/6/26/eaaz1002.full

[andrewflnr]

The hypothesis here is quite a bit more nuanced and specific than that. As a laymam, I found it worthwhile to read the whole article. In the course of making its case it touches on many fascinating topics. I found the case quite compelling, though I can't rule out that someone more familiar with the facts can poke holes in it.