S₁: Of men’s earliest inventions we know very little.

S₆: It was only a step further that he made a rude weapon by fastening a stone to the end of a stick.

P: Man used stick and stone long before he dared to meddle with fire.

Q: The first was to use a stone to crack a nut.

R: The next was the use of a stick to strike an enemy.

S: Once man had fire, he was the master of all lower creatures.

The proper sequence should be

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