The clade R1b-Z29560 (U152->Z193->Z192->BY10448->PF6652->Z29456->Z229460) is interesting. There are now 6 members in this clade with BIGY, but there is no further subgrouping. This seems exceptional, because most clades are bifunctional.
According to YTREE the TMRCA is 2500 BCE.
My suggestion: The MRCA was a historic person with great reproductive success.
Perhaps the celtic chieftain Brennus, who conquered Rome.
What do you think?