African cichlid fish are a great example to study how new species evolve. Scientists looked at 33 groups of fish that evolved a lot and 76 groups that didn't. They found that more new species appear when there are more different habitats in a lake. Also, new species form quickly at first, but then slow down as the lake gets full. Some cichlids are more likely to evolve into new species than others. This ability to evolve quickly is something they developed over time, not something they were born with.