My only issue with this statement is that it implies there were cats that sounded different from how domesticated cats sound now. I'm not really conviced of that. To my understanding they have a high pitch voice because they're small. For instance you can find videos online where they record a tiger "meowing" then they pitch it up to the register of a house cat. The resulting meow sounds nearly indistinguishable (other than the digital artifacts Inherent to doing such a thing) from a regular house cat's meow. Now tigers obviously didn't adapt to meowing like infants so my conclusion is that cats just sound like that and natural (human?) Selection had very little if anything to do with it.

Or: people who didn't respond to these meows didn't keep their cats and rats ate all their grain so people more responsive to the meows reproduced more...