Why Do Eggs Have Different Shapes?

STATES CHRONICLE – We have all seen eggs of different shapes and sizes, but have you ever wondered why they don’t look the same? A team of scientists has managed to discover the secret of these various shapes, and a bird’s ability to fly might be to blame.

In a new study published in the journal Science, researchers analyzed various shapes of eggs, as well as the birds which lay them. They discovered that the differences in flight ability among birds start early in a specimen, and determine the shape of its egg.

Two measurements when looking at egg shape

More precisely, a bird which is able to fly lays eggs of a rather elliptical or asymmetrical shape, while the eggs of those birds which don’t leave the ground are more spherical. Researchers found this very interesting, since eggs have the same function, regardless of shape. Even so, it seems that they evolve differently.

To establish this diversity among eggs, researchers characterized each object of their study in terms of two measurements. The first was ellipticity. An egg starts with a sphere shape and, then, it gradually becomes more elongated and elliptical. The second measurement was asymmetry, when one end of the egg might be pointier than the other.

What makes eggs have different shapes?

After analyzing eggs coming from 1,400 species of birds, they obtained around 50,000 different shapes. They were surprised to discover much variety among them. The shape found in most eggs was placed somewhere in the middle, meaning that it was neither perfectly spherical nor perfectly elliptical, and quite asymmetrical. In other words, the middle ground was quite similar to a chicken egg.

The membrane inside the egg is the one that gives it its shape. Also, the thickness and elasticity of this membrane is determined by the bird’s body mass or length of the wings, so flight ability directly influences the texture of the membrane, therefore the shape of the egg.

Flying birds are more aerodynamic, so their body is slenderer, which leads to an elliptical and asymmetrical egg. Also, such a shape allows for the egg to contain enough egg white and yolk and, at the same time, be suitable for flight.
Image Source: Wikimedia Commons