It is well accepted that birds evolved from dinosaurs, but the extent of the transformation still inspires wonder and awe. And new research.

One part of that transformation has just been traced in detail, showing that one of the things that happened in bird evolution was that their skulls pulled a Peter Pan and stopped growing up.

Some subtle genetic change slowed or stopped the development of the skull as a bird embryo grew in the shell and after hatching. The body kept on growing and changing proportions, but the skull changed only in size. It did not change in shape.

As a result, the skulls of birds look like those of baby dinosaurs. This kind of change is at the heart of the current understanding of how evolution proceeds, and although scientists are familiar with it from work on salamanders, fruit flies and other creatures, this new research shows how it occurred in two kinds of animals the public loves — dinosaurs and birds — bringing a complicated scientific idea home to the bird feeder and the museum exhibit hall.