A paradox

Flintstones, meet the Flintstones
They're a modern stone-age family
from the town of bedrock
they're a page right out of history
lets ride with the family down the street
through the courtesy of Fred's two feet
When you're with the Flintstones
have a yabba dabba do-time
a dabba do-time
You'll have a gay old time.

So how could they be modern and stone age at the same time?