Evolution and the Macaroni penguin

People often get confused about the meaning of evolution and natural selection - they assume that every trait in a particular organism must serve a particular purpose as the result of these inexorable, unerring processes. But that's not necessarily true. Sometimes genetic drift drives evolution and organisms wind up with traits that serve no clear purpose, and sometimes traits or structures may no longer serve a purpose but not be detrimental enough to be acted upon by natural selection (the appendix in humans is perhaps one of these). It is possible that the egg-laying habits of the macaroni penguins are a result of one of these alternative pathways. Some macaroni penguins lay two eggs, first one small, then one big, then discard the smaller egg. Since eggs usually represent the expenditure of significant amounts of energy for birds, why would these penguins waste time making an egg that won't ever hatch? Scientists aren't sure why some penguins do this, but they do know now why that first egg is so small. It's because penguins that lay the smaller egg are the ones that lay them immediately after coming back to land. The ones that wait a bit after returning to land have higher levels of a protein important for egg development and lay a normal-sized egg.

In any case, it's always interesting to try to understand the mysteries of evolution.