These six maps use default radius of 250km except for J1d where I adjusted the radius to 300km because I thought it would help smooth out the gradient in Central Asia.
In general I think 250km is good to use if there are enough data points.
For details on how the radius is calculated based on the area of the YFull MTree geocode, please refer to the documentation:
J1b has a very prolific lineage, J1b1, which accounts for most of J1b's presence in Europe. J1b is otherwise more frequent and has highest diversity between the Arabian Peninsula and Central Asia and South Asia.
J1b1 as a whole appears to have the highest frequency between the northern Persian Gulf of Iraq and Iran to the borders of Central and South Asia.
Note that per the mt Heatmap's actual computation, the highest frequencies are on part of the Greenland coast (edge effect from actual Iceland sample), Iceland and the Faroe Islands. This is caused by two ancient samples both of which are in the same branch J1b1a1a, TMRCA estimated 1200 ybp.
J1b1 has three children.
J1b1a1 has three children. J1b1a is by far the most prolific.
J1b1a1 has 25 child branches. This is too many to look at each one individually for me at this time. In the future I should develop a diversity map view for the mt tree that will facilitate the analysis of the deeper origins.
I will note that the two oldest samples are from Iron Age Kazakhstan, followed by an Iron Age sample from Grosseto, Italy.
One of the ancient samples from Kazakhstan, ESZ001, is in J1b1a1-a, which has highest frequency and diversity in a wide swath from Kazakhstan to the Persian Gulf.
In the Old World, J1b1a1a is only found in the British Isles, including in the Shetland Islands, Faroe Islands, Iceland and western Scandinavia.
J1b1a1b notably has two samples dating to 2250 ybp and 2200 ybp from Czechia and Hampshire, UK. It is found from Europe to Ukraine and Russia. No samples from Asia on the YFull MTree.
It seems challenging to me to theorize on the origin of J1b1a1 given that most of its lineages are found in Europe, yet the two oldest samples, in different branches, are found in Iron Age Kazakhstan, an area that is closer to the deeper diversity of J1b1.
It could be that many or most of the European lineages of J1b1a1 actually descend from a single, European origin MRCA that lived sometime after J1b1a1 and whose mtDNA didn't accumulate a traceable mutation.