Cave people hear animals making noises amongst themselves, wanting to be in on the pleasure, they begin making noises amongst themselves, showing off they can do that too. This feels stupid before long, so the cave people start letting their sounds mean something. A small language begins. The languages are very involved even by Biblical times, seemingly at some point in time humans were more, not less, mentally advanced than we are today. If you were fighting nature among beasts and animals and when in time you find yourself with child, you would not have time to or enough other human subjects to develop a very large vocabulary, unless you have a highly developed brain, perhaps. More than what we are all using today, maybe like the select whizzes who make the news, of which there aren't so many.
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