Inventions can be useful recombinations or applications of other inventions. They don't need to be wholly unique unto themselves. Indeed, the vast majority of them are not wholly unique.

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amelius 5 hours ago | parent [-]

We're talking about a millions year old invention here.

	▲	Dylan16807 4 hours ago \| parent [-]
		As far as the patent system is concerned, 20 years and a million years are the same thing. If you combine some million year old things in a new way, you can get a patent.