This Carson lineage is I2b1, Nordic. It does not connect with the R1b1 lines for many thousands of years back.
C-15, C-21 and C-27 are 34/37 and 33/37 matches so their common ancestor could be within a thousand years, but the paper trail has not yet confirmed who it is and likely never will.
There is an unusual development in this lineage. It appears that markers CDYa and CDYb (724) have fused back together. It was not a six jump step from 31-37 to 37-37, but likely just one. And not seven steps from 31-37 to 36-36, but likely only two. Family Tree DNA's ancestor predictor will not be accurate if comparing test results that do not have the same markers for CDYa and CDYb.
Further speculation on Haplogroup I - Lineage I-B should go here:http://www.worldfamilies.net/forum/index.php?topic=8399.0