Birthing A New World

I am quite frequently astounded at what comes out of my 7 yr old DS's mouth, both the good and the bad. Along with the requisite "poopy-head" and "pee-pee-face" (much to mommy's chagrin and requiring a stern look) usually directed at his siblings, he utters things out of the blue that generally cause me to stop and do a double-take. I am sure they are not out of the blue for him; they have probably been swirling around in his brain for some time before they reach my ears.
His latest? Watching a show on Science Channel about the rise and fall of dinosaur eras, "When an old world dies off, the earth gives birth to a new world." My response? " Uhhhh, yeah..." No question about it, just a sure uttering from his point of view.
Does anyone know if this is normal? I wonder if my other two will exhibit the same philosophical tendencies. I guess I will have to wait and see....