sentence1: Of course, if a researcher tampers with the evidence, making a unilateral, unsupported claim or assumption that a word means something that it does not, then that does not constitute semantic  it is what is known as dirty work at the crossroads, and M and S are indulging in a bit of mischief by suggesting that semantic change either has taken place or is taking place because they have some evidence that a certain change in usage had crept in.
sentence2: Semantic change happens when the meaning of word's changes to communities over time and false is not true .