PETERSON, PETERSEN, PETERSSON, PETTERSON, PETTERSEN, PETTERSSON, PIETERSON, PEDERSON, PEDERSEN, PETURSSON, and any other reasonable spelling variations are welcome to join the project. Only males have Y-chromosomes, so only male PETERSON/etc. can participate. If you are female, you can have a male PETERSON/etc. relative submit a sample for your line. To participate meaningfully, testees will need to share their direct male line ancestry back to the earliest known PETERSON/etc., as a pedigree (excluding living persons).