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!
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
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
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 -
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
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.
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,
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.
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
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.
1. "Wonderful Life — The Burgess
Shale and the Nature of History", Stephen Jay Gould, 1989,
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.
on the Burgess Shale", Simon Conway Morris and Stephen Jay
Gould, Natural History magazine, 107 (10): 48-55. A thrust
and parry exchange. Some acrimony.
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.
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.
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.
versus Science", Time Magazine, Nov. 5, 2006. A 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.
Astrobiology Institute Research Reveals Major Insight into Evolution
of Life on Earth", Press release, September 6, 2009.
"Two major classes of relatively simple microbes fused
together more than 2.5 billion years ago."
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:
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.
Lecture 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
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.