Q: Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
Sentence1: Macroevolution occurs over geologic time above the level of the species. 
Sentence2: Macroevolution is simply microevolution extrapolated over longer periods of time.
A:
Macroevolution