1,000,001: One to change the bulb and 1,000,000 to rebuild civilization to the point where they need light bulbs again.
or
One; she designs the bulb to crawl up the wall, unscrew the old one, and screw itself in.
or
They take short cuts!
or
What's the use, they'd still have bear feet
or
1,000,001: One to change the bulb and 1,000,000 to rebuild civilization to the point where they need light bulbs again.
or