Some facts fail to register the first time. Later, you encounter them again and your world tilts on its access. Try this one on for size: porters died out in Britain. Absolutely and utterly. Kaput. Apparently Jackson, writing about them in the 70s, was doing forensic work. Given porter's near-ubiquity in American brewpubs, I would say the style is in no immediate danger of re-extinction. On the other hand, it makes me hopeful for gose.