Many, if not most, white Carswells living in the USA are descended from Alexander and Isabella Carswell.
Two of Alexander and Isabella’s descendants have tested with the Carswell DNA project and both are congruent, haplogroup I2b. There is one mutation over 67 DYS markers. Further genealogical research will identify the specific points of line divergence, TMRCA and rates of change.
Many thanks to Tim Robbins, who has produced for us a broad historical overview of Carswells in the USA
In addition, the now defunct “Carswell Chronicle”s are currently being re-published in electronic format. This project is now finished and can be found here