According to legend, a janitor at the Institute for Advanced Studies in Princeton once asked: "So what is it all about then, Professor Einstein?" Undoubtedly, like most people, he wanted assurances that there is meaning and purpose in life, and that science was making progress in substantiating this.

Unfortunately, science by its very nature will never be able to answer questions such as "Why am I here?". Nevertheless, scientific discoveries have profound implications for our understanding of our own place in the cosmos. We now know that our sun is only one out of several hundred billion stars in our own galaxy, and that our galaxy is only one out of several hundred billion galaxies in the observable universe. It has been estimated that there are some 10²² stars in the universe - a 1 followed by 22 zeros.

The first planet orbiting another star was discovered in 1995. As of August 2009, 358 exosolar planets have been identified. We now have reason to believe that the number of planets in the universe is comparable to the number of stars.

The greatest question now confronting science is: "Are we alone?" It seems inconceivable that the Earth should be unique in harboring life, but to assess the chances of life evolving on other planets, and of complex life, we need to understand how Earth life originated and evolved. The starting point, of course, is Darwin's Theory of Evolution, arguably the greatest discovery in the history of science.

You may well wonder why I choose to discuss a somewhat controversial 20th century book on Darwinian evolution rather than "On the Origin of Species", which after all I had discovered in my Grandfather's library during my teens. — I have been thoroughly convinced of the validity of Darwin's theory throughout my adult life, but it is only after reading Gould's "Wonderful Life" (pointed out to me around 1990 by my colleague, Christer Magnusson), that I have come to fully appreciate the implications of Darwin's theory, and to question some of my own fundamental beliefs.

Hallucigenia, a Burgess Shale fossil named for its bizarre morphology. Later fossils indicate that the "top" appendages are actually legs, while the "bottom" spikes are protective, so the image is upside-down!

Drawing by Marianne Collins.

Gould's book deals with a particularly fascinating period in the development of life on Earth, known as the Cambrian Explosion, some 540 million years ago, when larger animals (visible to the naked eye) suddenly turned up in the fossil records. "It is as though an orchestra began playing without sounding a single note to tune up" (P. Ward). It was a period of extraordinary richness, when nature seemed to be experimenting with a large number of designs and body plans. All life forms that exist today have ancestors in the fossil record from that epoch. In addition, a large number of strange creatures without known descendants appeared within the space of just a few million years.

The Cambrian "explosion" presented a tough problem for Darwin's theory, which postulated a slow gradual process of evolution from simple organisms to increased complexity. Always the embodiment of honesty, he devoted an entire chapter of the Origin of Species to this enigma, and admitted that it could not be resolved at the present time, due to the imperfection of the fossil record. — We now know that the Cambrian explosion covers a longer period than a few million years, and additional fossil evidence supporting Darwin has been found. Still, the early Cambrian era was an era of extraordinarily rapid radiation and diversity.

Gould's book describes not only the rich fossils found at the Burgess Shale site in the Canadian Rockies. (By the way, I wonder how creationists explain the presence of marine fossils high up in the mountains? Did God plant a red herring to test believers?) It also recounts the cultural history of the site, how it was discovered, the field work and biographies of the paleontologists, and the various interpretations and implications of the findings. He manages to turn a dull scientific treatise into a wonderful journey of discovery, infusing us with his enthusiasm and leaving us baffled and bemused. (When I went to school in the 1950s, biology was a dull subject, a purely descriptive branch of science, a good example of what Lord Rutherford referred to as "stamp collection". There was no discussion of evolution, and the account of heredity ended with Mendel's experiments.)

A number of alternative explanations have been suggested for the amazing leap of the Cambrian "explosion". The concentration of oxygen or of nutrients may have reached a critical threshold, or ocean temperatures may have recovered after a period of global glaciation, or continental drift may have been a factor. The slow gradual evolution may have reached a breakout point. For instance, simulations indicate that once an organism has developed cells sensitive to light, the evolution of vision would follow very quickly, measured in geologic timescales. And that in turn could have triggered an arms race, leading to the development of exoskeletons etc.

The conventional "tree of life". Life has evolved steadily from simple to more complex forms.

Gould's alternative "bush" model for the Cambrian Explosion. Many strange lifeforms went extinct. Surviving life consists of variations of a few basic themes.

Gould makes three points in particular. One is the concept of punctuated equilibrium, a theory that he advanced together with Niles Eldredge in 1972. It states that rather than proceeding smoothly over time, evolution is characterized by episodes of rapid change interspersed with long periods of stasis, when organisms evolve at a much slower pace. Actually, this is in accordance with Darwin's view as expressed in the Origin of Species (ch. 4 and ch. 10). Evolution occurs mainly in response to environmental change, and if there is no change in the environment over millions of years, organisms would already be well adapted, and there would be little pressure for major modification. Of course, Darwin can only have had vague ideas about the stability of the Earth's environment over its history.

The other point is that the Cambrian Explosion really was a gigantic lottery, and that the outcome just as easily could have been completely different. Gould counts some 25 widely different animal body plans which were soon reduced to just the four that have survived to this day (vertebrates, exoskeletons, worms...), "all the others died without issue", i. e. went extinct. Why did some designs gain supremacy, while others were doomed to failure? Gould argues that the standard answer, i.e. that the surviving groups were better adapted to their environment, is unconvincing. There is no way to predict that a certain group is going to survive, while another is doomed to extinction. If the tape were rewound to the beginning of the Cambrian Explosion, and the dice were cast once more, it is highly unlikely that the outcome would be the same. [For my younger readers: a tape recorder was a 20th century device that preceded solid state memories.] Furthermore, organisms evolve to adapt to a particular environment. There is no correlation between adaptation to the environment and the ability to survive catastrophic environmental change. When the environment changes quickly and unpredictably, all bets are off. The dinosaurs held sway for more than a hundred million years until they were wiped out by an extraterrestrial impact 65 million years ago. In all probability, in the absence of catastrophe they would still dominate the domain of large-bodied vertebrates, leaving no room for the evolution of mammals with large brains.

Stephen Jay Gould (1941 - 2002).

The third point is that evolution has no inherent direction. The traditional view of the march of life toward ever increasing complexity, culminating in the emergence of homo sapiens some 50,000 years ago, is a misinterpretation of how evolution actually works. Intelligence, in particular, should not be seen as the culmination of the evolutionary process. In evolutionary terms, the higher animals are in no way better adapted than bacteria or plants. Our line of hominids is the outcome of one of Nature's myriad random experiments, and until quite recently we remained just a curiosity among the millions of animal species. "In Darwin's scheme, we are a detail, not a purpose or embodiment of the whole." — Over the eons there is a slow drift in the direction of greater complexity, but that is just the result of random processes similar to "the drunkard's walk" or Markov chains.

There are many intelligent animals. Consider the cuckoo which lays its egg among other eggs in a nest of a different bird species. The cuckoo egg hatches before the others, and the first thing the newborn cuckoo does, is to kick the other eggs out of the nest, thus eliminating competition for its foster parents' care. But this is hard-wired intelligence, pure instinct. In all probability, the young cuckoo has no sense of purpose. — Conscious intelligence is much more rare, and it is not clear that in general it gives much of a competitive edge in the struggle for survival and replication.

It is not surprising that Gould's view of the evolution of man as the result of blind chance and a series of improbable accidents — and that "rewinding the tape" would produce a quite different result — has run into strong opposition even among scientists. Simon Conway Morris, one of the heroes in Gould's book, points to functional convergence among different species as support for his view that regardless of genetic makeup, evolution does have a trend. Birds and bats are quite different groups, yet they have evolved wings for flight. Fish and dolphins have similar shapes, etc. Also, since Gould's book was written, many more fossils have been found and analysed. The Cambrian Explosion may have been a little more gradual and less explosive than previously thought, and the view that a large number of fundamentally different forms of life went extinct in short order has been criticized. — To me, the view that evolution inevitably leads to intelligence and consciousness seems colored by wishful thinking, however much I may wish the opposite to be true.

The cover of "The Crucible of Creation" by Simon Conway Morris.

Unfortunately, there have also been personal attacks on Gould having more to do with professional jealousy than with science — not an uncommon occurrence in the scientific community. Gould, who was a brilliant writer and speaker with a large audience, has been vilified as "the Sagan of the geosciences". (Carl Sagan was an astronomer with a gift for making science understandable and exciting to the general public. He held the opposite view from Gould on the prospects for intelligent life in our galaxy.) In addition, Gould, as a confirmed atheist and socialist, predictably triggered some strong animosity among religious and political opponents.

I must confess that during most of my adult life, I have accepted Darwinian theory without much thought, taking comfort in the implied view that evolution must have led to the emergence of countless intelligent and conscious creatures in the universe. Gould's view of the history of life as a fundamentally random process has certainly given me pause.

In 2000, Peter Ward and Donald Brownlee published "Rare Earth - Why Complex Life is Uncommon in the Universe". They argue persuasively, that far from the gradual, more or less predictable, progress of life from simple bacteria to homo sapiens that most of us have come to associate with Darwinism, complex life on Earth is in fact a result of a wildly improbable sequence of accidents. The good news is that simple bacterial life seems likely to occur on innumerable worlds. We might yet discover alien forms of life in our own Solar system. Ward and Brownlee are encouraged by the early development of life on Earth shortly after our planet's surface had solidified and cooled down to the boiling point of water. Also, the recent discovery of extreme microbes near deep-sea volcanic vents indicates that solar energy may not be necessary for life. These "archeans" seem to be a more primitive life form than bacteria and may have survived repeated sterilizations of the Earth's surface. Once bacterial life is established, it is extremely difficult to stamp out.

Ward thinks that there is a distinct possibility that alien bacterial life exists in the Solar system. He is critical of the fact that NASA's Genesis mission, which brought a sample of solar wind to the Earth in 2004, was not adequately protected from potentially infecting us with dangerous microbes.

In contrast, the evolution of complex life, such as animals, has been possible only due to an improbable chain of favorable circumstances. Earth life as we know it would not have been possible if our sun had not been of the right size to burn steadily for billions of years, and the Earth located far enough from the galactic center to be reasonably safe from cosmic radiation from energetic events and nearby supernovae. — We live in a narrow habitable zone in the Solar system. A little closer to the Sun and the climate would be too hot. A little farther out and our planet would be frozen. — The Earth's magnetic field shields us from lethal solar ultraviolet radiation.

Don Davis/NASA

Water probably was brought to the Earth by comet impacts. Throughout its history, our planet has been pummeled by asteroid and comet impacts. Our moon was created from the collision of a Mars-sized planetoid with the Earth. During the heaviest bombardment, which occurred early in Earth's history, its surface may have melted repeatedly. Any oceans would have been vaporized. As recently as 65 million years ago, the Earth was hit by an object that created a 180-km diameter impact crater and caused the extinction of the dinosaurs. A more severe extinction event occurred 250 million years ago, when 90 percent of all marine species died out. Yet, the Earth may have been fortunate. Simulations indicate that there would be many more objects crossing the Earth's orbit if the giant planet Jupiter had not been available at just the right distance from the sun. Jupiter absorbs or deflects comets and asteroids through its strong gravitational pull, sending some of them off into interstellar space, others on a collision trajectory with the sun. — The Moon may also have played a role, forcing the Earth's precession angle (governing the seasons) to be reasonably stable over geologic time scales. — Plate tectonics (continental drift) is thought to have been a key factor, acting as a planetary thermostat. When sedimentary rocks are subducted deep into the mantle, carbon dioxide is returned to the atmosphere. This tends to warm a planet that would otherwise become progressively colder. — The Earth has been provided with an adequate supply of iron, phosphorus and other substances needed by living organisms etc.

Of course, this "Goldilocks theory" (that the Earth is just right for complex life while few other planets are likely to be similarly favored) is far from universally agreed upon. It is awfully risky to base a statistical argument on a sample of one. Until recently we had no idea that there is primitive life powered by volcanic vents on the sea floor, and life itself may find ways to evolve which we cannot imagine. — I have previously discussed the probability of intelligent life in our galaxy elsewhere on this web site.

As long as there is a sense of direction and purpose to biological evolution, most of us are willing to accept it as a well-established fact. (Although one of my nieces as a child said: Dad says that we come from apes, and apes came from dinosaurs. But where did the dinosaurs come from? Nah, I still think God did it.) Even the Pope now embraces evolution. It is the view of evolution as a random process without direction or purpose that is creating resistance even among educated people. But it is interesting that Mark Twain wrote: If the Eiffel Tower were now representing the world's age, the skin of paint on the pinnacle knob at its summit would represent man's share of that age; and anybody would perceive that the skin was what the tower was built for. I reckon they would, I dunno.

Charles Darwin (1809-1882) around the time of the publishing of "On the Origin of Species" in 1859.

Darwin was ambiguous on this matter. He acknowledged the existence of general laws that regulate life in a broad sense. But the details lay in a realm of contingency undirected by laws, i. e. chance. "I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars." He was very reticent on the subject of religion. He mentions the Creator in On the Origin of Species — but not in the first edition. In his autobiography he describes himself as an agnostic. He had two strong reasons not to challenge religious beliefs outright: his wife was intensely religious, and he knew that On the Origin of Species would create a furor when it was published in 1859. By then he had spent over 20 years compiling his evidence for evolution, and when the book was published, he presented it as an abstract of a more complete treatise to follow. When he let a few friends in on his secret, he described it as "confessing to murder". His resolve to publish may have been strengthened by the devastating death of his 10-year old daughter in 1851.

Of course, science can never rule out the possibility of divine intervention. The supernatural is by definition beyond the realm of nature, but the need to turn to supernatural causes to explain natural processes has never been smaller.

According to Christian faith, "not a sparrow will fall to the ground apart from the will of your Father". In a German novel describing the battle of Stalingrad, I once read about a soldier who told the chaplain. "For me, God has died at Stalingrad." The chaplain replied: "Yes, you are right, he has died here, but not just once. He has died together with every soldier who died here." Personally, I find that kind of compassionate god much more appealing than an omnipotent puppet master; a god who listens to prayer rather than performs miracles à la carte in response. "Please God, let my team win!" — For those who prefer an interventionist god, well there is still the Big Bang and the Laws of Nature. In an article in Scientific American, I saw the Big Bang explained as "a quantum fluctuation". Somehow, that seems a little flat...

I cannot close without mentioning a fascinating 20-year ongoing experiment showing evolution in action and lending support to Gould's thesis that the outcome would not be the same if "the tape were rewound". The paper was published in 2008. From the abstract:

Public acceptance of evolution theory in Europe, Japan and U.S.A. in 2005.

Jon Miller, et al./Science

One of the difficulties in evolution theory is to explain how complex structures can evolve in small steps, each of which enhances "fitness". This has been referred to as "climbing Mount Improbable". If several steps were needed to achieve a positive effect, one would expect that either several mutations would have to occur simultaneously, which would border on the miraculous, or one mutation would stay dormant through successive generations until a second mutation, perhaps much later, would complete the step forward in combination with the first mutation. It is this second scenario that has now been experimentally verified. It means that evolution can proceed in larger steps, where a number of mutations are involved before a beneficial change is effected. The experiment clearly disproves a claim made by the intelligent-design school of thought: If the development of many of the features of the cell required multiple mutations during the course of evolution, then the cell is beyond Darwinian explanation.

Darwin's theory of evolution is now universally accepted among scientists, based on its predictive power, and based in particular on evidence from molecular biology. Among the general public it is not uncommon to hear it questioned: "After all it is just a theory". But so is the theory of gravity. In science there are no sacrosanct truths, only models that best fit the available data. After 150 years, the theory stands unchallenged and rock solid.

Further reading

1. "Wonderful Life — The Burgess Shale and the Nature of History", Stephen Jay Gould, 1989, ISBN 0-393-02705-8.
2. "Rare Earth — Why Complex Life is Uncommon in the Universe", Peter D. Ward and Donald Brownlee, 2000, ISBN 0-387-98701-0.
3. "The Crucible of Creation — The Burgess Shale and the Rise of Animals", Simon Conway Morris, 1998, ISBN 0-19-850256-7.
4. "Showdown on the Burgess Shale", Simon Conway Morris and Stephen Jay Gould. A thrust and parry exchange. Some acrimony.
5. Blount ZD, Borland CZ, Lenski RE (2008), "Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli." Proc Natl Acad Sci U S A 105(23):7899-7906. The scientific paper on the experiment mentioned above.
6. Carl Zimmer, "A New Step in Evolution", June 2, 2008. A detailed description of Lenski's experiment with a link to a follow-up article with responses to readers' comments.
7. PZ Myers, "Historical contingency in the evolution of E. Coli", June 10, 2008. A passionate biologist in arms against creationism. The article explains the significance of Lenski's experiment, with 166 reader's comments.
8. A 2006 debate between Richard Dawkins, a militant atheist (author of "The God Delusion"), and Francis Collins, Director of the National Human Genome Research Institute and a Christian.
9. Astronomy magazine 2009. "Two major classes of relatively simple microbes fused together more than 2.5 billion years ago."

Video lectures

One of the blessings of living in the age of the Internet is the access it offers to excellent video lectures. Here is a list of what I have been enjoying lately:

10. The Howard Hughes 2005 Holiday Lectures on Evolution. Sean B. Carroll and David M. Kingsley. Four 1-hour lectures with an audience of gifted high-school students.
11. Darwinism talk in 2009 by Richard Dawkins.
12. "The Undesigned Universe", Peter Ward (co-author of "Rare Earth"). A three-part lecture at Princeton, January 9-11, 2007. Each part runs 1 h 30 min. Part 1. Part 2. Part 3.
13. Ten lectures on Darwin's Legacy. Stanford University, 2008. Around two hours each. Lecture followed by panel discussion. Robert Siegel, William Durham, Eugenie Scott, Janet Browne, Daniel Dennett, Peter and Rosemary Grant, Niles Eldredge, Melissa Brown, Paul Ewald, Russell Fernald, George Levine.

"Books" start page