Scientists believe they have answered a question that has been around since the time of Aristotle: why are bird's eggs egg-shaped? After extensive research they have concluded that the egg shape fits better inside a sleek bodied flying machine, according to research published in the Science. By simplifying egg morphology to two variables — their symmetry (the difference between the pointed and blunt end) and their ellipticity (how long and oval the egg is), the researchers compared over 49,000 photographs of eggs covering 1400 species of living and distinct birds. The found that, of all the characteristics that differed among the birds, the shape of the wing matched the differences in asymmetry and ellipticity of the eggs best. To find out more go to Avian egg shape: Form, function, and evolution.