I think there's something about having a second kid that helps you spot certain distinct looks and faces earlier than you could with the first. The lower-lip-out face seems to be shaping up as Silas's look of serious concentration (this older picture feels like an early prototype). In the above picture, the look is functioning as his King Kong, I'm gettin' busy face as he bangs stuff together. He's just starting to master hand clapping, but he's had banging-things-together-to-make-noise down for months now, it seems.

Picture taken April 15, 2006.