Prevent all damage that would be dealt this turn by non-Human sources.
If a spell or ability causes damage to be dealt, it will indicate what object deals the damage. The object dealing damage might not be the spell itself.
Sources that have no creature type at all are non-Human sources, as are sources with creature types that don’t include Human. A creature that is Human and has other types, such as a Human Werewolf, is still a Human source.