If you look closely, there is nothing extraordinary about an animal that lays eggs and nurses it's young.
For the platypus, this has been the ordinary way of life for over 100.000 years. What happened? The scientists
that devised the classification system used in biology divided the animal kingdom into mammals that nurse their
young on one side and animals that lay eggs on the other side. They never expected the existence of the platypus
(or, for that matter, the existence of the only living relative of the platypus, the Echidna.)
These animals broke the boundaries of the biological classification system of the day. It - literally -
was outside the box. The scientists chose to hold on to their classification system despite clear evidence
that the system did not accurately reflect reality.
To us, the platypus is a constant reminder to change our vantage point and perspective, to think outside