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The rings on a tree stump tell more than just age. Dendrochronologists (those who study trees) use all the visual information tree rings offer to learn about periods of excessive rainfall, draughts, cloudiness—basic climate indicators recorded in the manner/rate of growth of a tree’s rings. Comparing patterns in known trees, researchers can overlap those patterns and go back hundreds of years to date trees and the environment in which they grew. It’s been a definitive factor in determining the age of several archeological sites.

Researchers attempting to answer how eggs might acquire varying shapes initially identified two parameters that could influence egg form: variations in the membrane’s composition and differences in pressure applied to the membrane before the egg hatches.

Researchers also looked into why egg shapes might be so spectacularly diverse. Turns out egg shape was strongly correlated with a measure of wing shape, called the hand-wing index, that reflects flight ability. In order to fly, they must maintain sleek bodies—meaning their eggs can’t be too wide.