Natural selection – that merciless weeder-outer of biological designs that are out of step with the times – also is a wily shaper of traits. Exhibit A is the pointy murre egg, according to new research published in the Journal of Experimental Biology.

Common murres and thick-billed murres tend to nest in tightly packed colonies on craggy seaside cliffs. The ledges on which they lay their eggs can be quite narrow, sometimes “as shallow as the egg is long,” the authors of the new study wrote.