The humans here are sufficiently similar in appearance and behavior to dath ilani humans that the divergence point couldn't have been more than a few tens of thousands of years ago.  Those humans would have already been adapted to eat cooked meat, and brought fire with them.

It's probably been around in Golarion for as long as humans have been around in Golarion, which isn't actually very long.

The humans here are sufficiently similar in appearance and behavior to dath ilani humans that the copying time of their ancestors couldn't have been more than a few tens of thousands of years ago, relative to Keltham's now-time out of dath ilan.  Those humans would have already been adapted to eat cooked meat, and brought fire with them.

It's probably been around in Golarion for as long as humans have been around in Golarion, which isn't actually very long.