(The text of a talk given at CWRU’s Share the Vision program on Friday, August 22, 2008 at 1:00 pm in Severance Hall. This annual program is to welcome all incoming first year students. My comments centered on this year’s common reading book selection The Reluctant Mr. Darwin by David Quammen.)

Welcome to Case Western Reserve University!

You are fortunate that in your first year here you are going to part of a big year-long celebration, organized by this university, to mark the 200th anniversary of the birth of Charles Darwin and the 150th anniversary of his groundbreaking book On the Origin of Species.

In my opinion, Darwin is the greatest scientist of all time. You have no idea how hard it is for me to say that because I am a physicist and had long thought that the only competitors for that exalted title were Isaac Newton and Albert Einstein. But the more that I have learned about the theory of evolution over the last decade, the more I have to concede that Darwin has had the most impact on our thinking.

As you have heard today, the Share the Vision program at Case is part of the university’s commitment to create a welcoming and unifying environment for people from all backgrounds. Darwin’s ideas should be warmly welcomed by those who share those goals because one important implication of his work is that all of us are biologically linked because we all share common ancestors.

If any two of you in this auditorium could trace your ancestors back in time, it will not be long before you find that you share a common ancestor. In fact, we would find that everyone who lives in the world now shares at least one common ancestor who lived only as far back as around 1500 AD. So around the time of Copernicus and the Renaissance, some one was walking around who is the common ancestor of each and every one of us.

If that doesn’t boggle your mind, then listen to this. If you go back to just around 3,000 BC, of all the people who lived then, about 20% have no living descendents. Their lines died out. But the remaining 80% are the shared, common ancestors of all of us. Think about that for a minute. This is quite amazing. We are all, literally, part of one big family. We are all cousins under the skin.

It gets even better. If we go back even further, we find that we are cousins with all the nonhuman animals as well, and going back further still, with all the plants and even bacteria, all of us tracing our ancestors back to possibly a single ancestral organism. All of life that presently exists and ever existed is connected by this tree of life.

No wonder that Darwin was moved by this stupendous insight to end his book On the Origin of Species, by saying, “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

But, sadly, not everyone is as delighted as I am with the idea that worms are our cousins, and that we are both part of one big family with every organism that ever lived. Those who want to believe that humans possess some unique and special quality not possessed by other animals have found Darwin’s idea deeply disturbing, and this is the source of much of the antagonism to him. Even the cautious Darwin himself, aware of this problem and the hostility it would arouse, only obliquely hinted at the linkage of humans to all other species in On the Origin of Species, leaving a full treatment to a subsequent book The Descent of Man published twelve years later.

Darwin’s theory of natural selection and the tree of life is not only eminently plausible, but has been put on a rigorous mathematical footing and has abundant evidence in support of it. So why does the theory still arouse such strong opposition?

The superficial answer is that Darwin’s theory goes against the religious belief that each species, and especially humans, were the result of a special act of creation by god. That idea seemed plausible at a time when it seemed obvious that every complex thing needed an even more complex designer to create it. But with Darwin, for the first time we had a scientific theory that showed how complex things could emerge from simpler things, without any outside intervention or agent or intelligence or design. Once the first primitive replicator, an early ancestor of DNA, had been created in the primeval soup, it multiplied and diverged, under the action of purely physical and algorithmic laws acting mindlessly, to eventually become the wide array of life we have now.

What is even more unnerving to some is that Darwin’s theory reaches into every aspect of existence. As philosopher Daniel Dennett says, it is like an immensely powerful acid that once created cannot be contained by any boundaries because it can eat through any wall. People first tried to restrict it to nonhuman life but it broke through that barrier. They then tried to restrict it only to the human body but it broke through that too. Darwin’s theory is now being applied to explain the origins of language and altruism and morality and other aspects of behavior, and to the workings of the brain and mind and consciousness.

Even intelligence, the feature that humanity prizes itself upon and which had been thought to be a precursor to creation, we now know occurred much later in life’s evolution and came into being as a result of the same non-intelligent, undirected, natural selection mechanism that produced our arms and legs.

There seems to be no quality that we humans possess that could not have come into existence by the evolutionary processes described by Darwin and his successors.

Darwin’s theory has extended even to what used to be considered purely philosophical questions. Paleontologist George Gaylord Simpson said that all attempts before the publication of On the Origin of Species to answer the question of what does it mean to be human were worthless and that we would be better off if we ignored them completely. Such is the significance of Darwin’s work.

People who are wedded to the idea that human beings must possess some unique, non-material, and possibly divine quality, and that there must be some externally imposed purpose to their lives and the universe are highly uncomfortable by these developments. As cognitive scientist Steven Pinker says, “People desperately want Darwin to be wrong . . . because natural selection implies there is no plan to the universe, including human nature.”

But the fact that the theory of evolution causes unease for some is hardly grounds for its rejection. The test of validity of a scientific theory is not whether it is perfect or whether it explains everything or whether it makes us feel happy or satisfies some deep emotional need, but whether it works better than any of its competitors. And there is nothing that comes even close to replacing the neo-Darwinian synthesis as the explanation of life’s diversity.

As you will have read in the book, Darwin was nervous about where his ideas were taking him, even though he was increasingly convinced that he was right. He knew that in science just having a good idea isn’t enough, however beautiful the idea is. You had to have evidence to support it and to that end he doggedly spent most of his life, observing, experimenting, and collecting data from all over the world, despite ill health and recurring headaches and vomiting attacks and personal tragedy.

Since his death, the evidence in favor of his theory has increased with other revolutionary discoveries like genes and DNA and continental drift and fossils. The evidence in support of Darwin’s theory of natural selection and the resulting interconnectedness of all life now exists in abundance.

This has not stopped the critics though. But they have been reduced to merely trying to find problems as yet unsolved by the theory of evolution because no alternative theory has been able to produce the kinds of evidence necessary to be taken seriously as a competitor. But as Herbert Spencer pointed out as long ago as 1891, “Those who cavalierly reject the Theory of Evolution as not being adequately supported by facts, seem to forget that their own theory is supported by no facts at all.”

This year, you will all be able to be part of the Darwin celebration as eminent scientists, philosophers, and legal scholars from all over the world come to Case to discuss all the ramifications of his work. You have a unique opportunity to be part of that exciting year and I hope you take full advantage of it.

POST SCRIPT: Teaching evolution in high schools

Florida has just introduced evolution explicitly into its science standards. This story illustrates one teacher’s efforts to teach it to his high school students.