We love birthdays and anniversaries , especially ones that end in zero. This year there are two such numbers related to Charles Darwin-200 years since his birth and 150 years since publication of Origin of Species. Of course there is all sorts of commentary and there should be. After all Darwin's way of looking at the world really did revolutionize biology and society as a whole.
What was it really that Darwin did that was so great? After all he wasn't the first person to speculate that evolution happens, or even to propose how it might happen. Maybe he was just the right person at the right time to be remembered. But I think there is more. Perhaps the best way to answer the question from my perspective is to briefly contrast Charles Darwin with Jean Louis Agassiz. Agassiz was one of the most popular scientists of the 19th century, especially in biology, Harvard Professor, did lots of important work on fossils and glaciation. Yet he never accepted evolution.
I encountered Agassiz in Edward Lurie's biography, Louis Agassiz: A Life in Science. Lurie observed, as I recall, that Agassiz was a proponent of the notion that the geological features of the Earth were molded mainly by a series of catastrophic events and that that the distribution of species could be best explained by a series of creation events. As new data about geology and the distribution of species came out-Agassiz would simply postulate a new catastrophe or a new creation event. So the data are explained.
Darwin was different. Not only did he synthesize masses of data to support his ideas, but he confronted the weaknesses in his ideas head on. After all, Darwin knew that contradictions between observation and theory are not to be feared but provide new opportunities to learn by empirical means what makes the universe work. Agassiz was an accomplished scientist as well and probably understood this idea as well. The difference is that Agassiz did not understand the universality of the principle that contradictions provide new opportunities in all spheres of science, and, I argue, life as well.
So happy birthday Mr. Darwin and here's to biologists today who see contradiction as something not to be feared, or glossed over with rhetorical tricks, but as opportunity for understanding.