Maykop: a multi-ethnic layer cake?

Let's speculate about the linguistic affinities of the currently available ancient populations from the Caucasus and surrounds. I put together a series of outgroup f3-stats to help things along. They're available for download here.

Maykop
Georgian 0.258224
Abkhasian 0.257899
Latvian 0.257376
Swedish 0.257301
Turkish_Trabzon 0.256996
Basque_Spanish 0.256589
Chechen 0.256514
Icelandic 0.256418

The Steppe Maykop enigma

Who were the Steppe Maykop people exactly? Their ancestry must surely rank as one of the biggest surprises served up by ancient DNA to date.

I always thought that they'd turn out roughly like a mixture between populations associated with the Kura-Araxes and Yamnaya cultures (mostly because their territory was located sort of in between them). Nope, that wasn't even close. This is where they