Origin of Hemoglobins: A Repeated Problem for Biological Evolution
It’s football season again! And one of the big questions on every fan’s mind is, Can the New Orleans Saints repeat as Super Bowl champs? Even though the Saints are expected to have a good season, it is hard for any team to win the Super Bowl in back-to-back years. The last team to accomplish this feat was the New England Patriots.
Repeating as NFL champions is difficult because each season is filled with contingencies. Star players can get hurt, the referees can blow a call at a key point in a key game, bad teams can catch a lucky break, etc.
Evolution Doesn’t Repeat
The evolutionary process shares something in common with the NFL season: it too is characterized by contingencies. Late evolutionary biologist Stephen Jay Gould espoused the concept of historical contingency in his book Wonderful Life.
According to historical contingency, chance events govern biological and biochemical evolution at its most fundamental level. Evolutionary pathways consist of a historical sequence of chance genetic changes operated on by natural selection, which, too, consists of chance components. As a consequence, if evolutionary events could be repeated, the outcome would be dramatically different every time. The inability of evolutionary processes to retrace the same path makes convergence—the repeated and independent appearances of the same biological and biochemical designs throughout nature among unrelated organisms—highly unlikely.
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