Maju, who is in addition to being a public intellectual, a Basque person who is fluent in the Basque language, discusses the possibility that the hypothetical Vasconic language family of which Basque is a part and all other members are extinct, may be derived from the Nilo-Saharan Nubian languages of Africa, with substantial later contributions from Proto-Indo-European (as opposed, for example, to its later variants), i.e. a Vasco-Nubian hypothesis.
He suggests a Mesolithic (i.e. immediately pre-invention of farming) presence in the Levant of Nilo-Saharan language speakers, whose language becomes the language of the first farmers of Europe and then is bit by bit replaced by Indo-European languages at a later date.
He makes an effort at mass lexical comparison with a Swadesh list of words that shows a much stronger than random chance relationship. I've looked at the phonetics and grammar and it isn't too much of a stretch on that front at that time depth.
No one is declaring this conjecture to be "the truth" at this point, but the evidence is serious enough that it has leaped to the front of the line as a viable hypothesis compared to other existing hypothetical proposals. He has also used mass lexical comparison to pretty much definitively rule out several other hypothetical connections between Basque and other language families that have been proposed by credentialed linguists but don't deserve serious consideration.