It had long been presumed that stone tool-making was a hallmark of our ______________, Homo. _______________,the recent discovery, in northwestern Kenya, of 3.3-million-year-old stone tools that are 7,00,000 years older than any other such stone tools ever found suggests it was the more ancient human ancestors who made the cognitive leap needed for crafting such implements.

1. genius, per contra
2. genius, additionally
3. genus, after all
4. genus, however