So it is much more likely that the fossil record exhibits saltational events, and gaps are not merely the result of inadequacy of fossils. Constraints to evolution. The 3-dimensional cube describes a set of possible shell shapes. Drawn by computer. But almost always can find hidden saltational events.
Populations move between adaptive peaks.
Historical change in adaptive topography leaves a species stranded on a local peak. The species is stuck at a local peak because selection does not favor evolution to the global peak. Adaptive landscape A 2-peaked fitness landscape with local and global maxima. Natural selection will take a population with gene frequency p towards a local peak, and away from the peak with highest average fitness. Lake Nagugabo near Lake Victoria has 5 endemic cichlid fish, although lake is only 4000 years old.