At some point during this boring era, humans decided that they wanted to see God on their own terms. So they decided to build a skyscraper to heaven or the gateway to the alternate dimension or wherever God spent most of Its time. Even though this seems like a hair-brained scheme, God thought it would work or at least was pissed at their arrogance, so It decided to make communication too difficult to continue by inventing different languages. Apparently, before this everyone still spoke Indo-European or some other proto-language, which suggests this story is out of chronological order, but whatever.
Then a bunch more people were born.