Fringe: Were the First People Shapeshifters?

My whackadoo theory for the week is that the First People were shapeshifters. If Sam Weiss turns out to be a First Person, this would explain his comment that he's "taller" and "older" than he looks.

Maybe Sam was the source of the shapeshifter technology that Belly gave to Walternate. Perhaps the hybrid soldiers use technology to do what the First People evolved to do naturally.