How can evolution produce complex organs like the eye?
In the process of natural selection, individuals in a population who are well-adapted to a particular set of environmental conditions have an advantage over those who are not so well adapted. These individuals pass their genes and advantageous traits to their offspring, giving the offspring the same advantages. Generation after generation, natural selection acts upon each structure within an organ like the eye, producing incremental improvements in the process. Each tiny change in a structure is dependent upon changes in all the other structures. In this way, individual parts of a system evolve in unison to be both structurally and functionally compatible. Eventually, over thousands and sometimes millions of years, the small improvements add up — the simple, systematic process has produced an almost unfathomably complex organ. Recently, scientists have found clues to the evolutionary pasts of some of the most complex organs, helping to clarify how this process works.
