@Maciamo,
I don't think there's any proof it was specifcally R1b people who domesticated cattle, given that cattle came to Europe with the earliest Neolithic, nor do I see how they could have brought metallurgy in the earliest periods given that the earliest samples on the steppe showing a change in ancestry are from a period when their only metallurgy was imported from the Balkans.
The strongest evidence that R1b people domesticated cattle is that R1b-L23 Yamna people were cattle pastoralists AND R1b-V88 tribes in Africa are also cattle pastoralists to this day. Obviously domesticated animals and crops were readily exchanged between tribes in the two and a half millennia (9500-7000 BCE) preceding the Neolithic expansion beyond the Fertile Crescent. Farmers couldn't have come to Europe with cereals, legumes, goats, sheep, pigs, cattle and also pottery if each of them were domesticated (or invented for pottery) by separate tribes at various locations in the Fertile Crescent. And we know that there were many independent tribes (E1b1b, G2a, H2, J1, J2a, J2b, L1a, R1b, R2) in the Middle East at the time, and that cereal cultivation arose in the southern Levant, while cattle were domesticated in northern Syria and goats in the Zagros (western Iran), and the first pottery came from northern Iraq. There must have been a lot of exchanges between tribes. Well, a lot is relative as it took them 2500 years to get the full Neolithic package relatively evenly distributed over that region. It doesn't matter how quickly it happened. My point is that whoever domesticated cattle in northern Syria, those cattle could easily have ended up in all Neolithic tribes before the Neolithic expansion. What is more surprising is that R1b tribes decided to remain primarily cattle pastoralists wherever they went (Europe, Africa, Central Asia) and did not really care for land cultivation, nor other animals (they did keep some sheep in Yamna, but mostly for the wool, as they still do in Scotland and Ireland).
As for metallurgy, I don't understand why you are telling me that. I have never said that R1b people invented metallurgy. Only
bronze metallurgy, and that was probably in Maykop, where R1b-L23 would have started associating with G2a-U1. So it could have been the G2a-U1 who were the metal workers who originally invented bronze too. If you check
this thread from early 2010, I already proposed that G2a (what was then G2a3b1 but is now known as L140) were the metallurgist accompanying the R1b stockbreeders in the PIE migrations. It's a well established fact that copper metallurgy arose in the Balkans and central Anatolia, two regions where G2a was dominant at the time.
However, I think the handwriting is on the wall that all the genetics labs are looking at a movement from the south onto the steppe carrying a new genetic element. In the hobbyist world it's been vociferously argued that this all came via West Asian women. I've argued many times that there are a lot of problems with that theory, not least of which is the fact that there is a lot of mtDNA U5 and U4 on the steppe, and not enough south of the Caucuses mtDNA to account for the large percentage of CHG. Maybe they'll find a big group of J2b somewhere, but if not your hypothesis is a possibility. People forget how quickly the y can become decoupled from it's original autosomal signature.
I don't understand what U4 and U5 have to do with CHG admixture. IMO, CHG admixture came in two waves to the Steppe. The first was an early Neolithic migration of J2b from NW Iran. The second was a middlle Neolithic migration of R1b-L23 from Armenia/NW Iran/Azerbaijan to the Steppe (see above post). The first wave would have brought lineages like N1a (or I), and perhaps also T1a, T2 and W. The second would have brought J1b1a, H2a1, H4, H8c, H15, T1a, T2c, as well as I and W.
I don't support the theory that R1b men from the Steppe crossed the Caucasus to steal West Asian women. That is ridiculous. If R1b-M269 evolved for 7000 years around the South Caucasus (see above post), there is no way they wouldn't have intermarried with West Asian women.