My source is simple observation. I did all the mowing as a kid, acres every week. In the spring, chopping down all the new dandelions was satisfying and the grass looked great. By the middle of the summer, dandelions were back but now they were strangely 'smashed' ones that grew no taller than 4", with flattened stems that turned or curled or flowers on short, short stems that bent over.

I'm sure that gene was always there; but billions of mowings over a century of lawn care means its present everywhere. Simple selection?