At some point, you can't lift this boulder with just your own strength. And if you find that you need to move bigger and bigger boulders up hills, you will need more and more help.
“While we were at work there came nine or 10 of the natives to a small hill a little way from us, and stood there menacing and threatening of us, and making a great noise. At last one of them came towards us, and the rest followed at a distance.”