I recently matched on 35 out of 37 Y-DNA markers with a Porter (both of us had our DNA tested by the same company). The most recent common male ancestor appears to have lived between roughly 12 and 16 generations ago (that is, 300 to 400 years ago). The likelihood of a common ancestor at 12 generations ago is 90%, and goes up very slightly with each previous generation. The likelihood of having a common male ancestor at 24 generations ago (that's about 600 years, assuming 25 years on average per generation) is 99.77%!
In my research, I've seen my own family surname as Portis, Portris, Portas, Porthouse, Portues, Portues and about 20 to 30 other spelling variations (including Porteons, where the 'r' has looked to the transcriber like an 'n').
I can see how easy it would be for Portis to become Porters, and then to see the final 's' dropped through serendipity.
Has anyone else come across any Porteous records in their Porter research?
P.S. I've corresponded with the person who submitted their Porter relative for a DNA test. The late 19th century photos of Porter males that I received bear a very strong resemblance to my brothers.