darwin's dilema script
TRANSCRIPT
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DARWIN'S DILEMMA Subtitle master/ FINAL 10/17/2009
1. Narration
An ancient mystery is etched upon these mountains. Astory of primordial oceans and
prehistoric life.
Of creatures stranger than fictionand the controversy that has surrounded them for
more than a century.
2. Narration
Buried among these majestic peaks are glimpses of an event that transformed the
planet in a moment of geological time.
Compelling evidence, etched in stone, that challenges long-held assumptions about theorigin of animal life on earth.
3. Narration
Today, most paleontologists think that complex animals first appeared on earth about
530 million years ago during a geological period known as the Cambrian.
But early in the 19th
century, little was understood about this seminal event in the
history of life
4. Narration
In 1831, the renowned geologist Adam Sedgwick began to excavate theCambrian
rock strata in northern Wales.
He was assisted by Charles Darwin, a recent graduate of Cambridge University.
5. Narration
For the young Darwin, the fossils embedded in the Cambrian shale were an intriguing
curiosity.
But, at 22, he lacked the perspective to appreciate their full significance.
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6. Narration
Natural selection, the theory of evolution, and the Origin of Species, all lay years
ahead. So he couldnt imagine that the stones beneath him held a mystery he would
never resolve.
7. Narration
It was a mystery Darwin would ponder into old age and then pass on to future
generations. The mystery of the Cambrian explosion.
8. Simon Conway Morris
The Cambrian geological interval is just great in terms of the fossil record because
thats when animals effectively first colonize the earth.
Its a very exciting time and, by and large, scientists like to work in vividly,
interesting areas where theres a hum about the whole thing, and thats very much thecase with the Cambrian at the moment.
9. Narration
Simon Conway Morris has devoted his career to the study of evolution and the early
history of life.
Morris has staged expeditions on four continents and surveyed the intervals of
geological timewhile focusing his attention on the Cambrian period and evidencefor the sudden emergence of animals in a veritable explosion of life.
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10.Simon Conway Morris
The Cambrian explosion is exactly what it says it is. Its an explosion. Now, not an
explosion in terms of pieces of animal flying all over the place. Actually, when
biologists talk about an explosion what they mean is, effectively, an enormousdiversification-what we call a radiation. So we have during the Cambrian what
appears to be the abrupt appearance of animals,
Were filling the barrel with lots of different types of organisms. But were alsoinventing nervous systems, were inventing eyes, were inventing how to move
quickly. So the whole world is speeding up. Its an event where in many respectseverything changes forever.
11.Narration
More than a century ago, a stunning window to the Cambrian explosion was openedby a series of discoveries made in western Canada.
In 1886, the Canadian Pacific Railroad reached British Columbia and the KickingHorse valley. For the first time, eastern and western Canada were linked by a 2500
mile steel artery that opened the Rocky Mountains to tourists, adventurers, and men of
science. Among them was the geologist, R.G. McConnell
Earlier in the year, McConnell had heard reports of a shale bed on the flank of Mt.Stephen, just outside the town of Field. Railroad carpenters, who had explored the
area, said it was filled with stone bugs.
In September, McConnell climbed the mountain. To his amazement, he found
unmistakable imprints of prehistoric life on most of the shales in the bed. McConnellwas standing in an ocean of fossilized trilobites.
12.Simon Conway Morris
Trilobites are iconsof the Cambrianand there are billions of trilobites high up on theshoulder of Mt. Stephen. One reason for that is that as they grew they periodically
threw off their old skeleton and made a new skeleton. So basically they made many
fossils throughout their individual lives.
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13. Narration
McConnell collected hundreds of these fossilsand sent many of them to other
scientists for examination.
News of his work soon reached the offices of the United States Geological Survey and
Charles Doolittle Walcott, a leading expert on Cambrian paleontology.
Walcott was fascinated by McConnells reports, but had to wait almost 20 years forthe opportunity to conduct his own research. Finally, in 1907, as the newly appointed
secretary of the Smithsonian Institution, he boarded a train for western Canada
14. Narration
Walcott spent two summers at Mt. Stephen collecting fossils and surveying the
geology of the area. Yet, despite his success here, he knew his exploration of thesemountains was only beginning.
Lookingoutacross the Kicking Horse valley to the Burgess Pass, Walcott set hissights on a corner of the Rockies untouched by the hammer and pick of any geologist.
This is where he would move his expedition.
15. Narration
On August 30, 1909, Walcott led his team below this ridge
15 miles north of Mt. Stephen. There, legend holds, he stopped to examine a pile of
shale that blocked the narrow horse trail. As he picked up a slab, the geologist noticed
a faint, but well-defined fossil he had never seen before. A delicate lace crab he laternamed, Marrella.
16. Simon Conway Morris
He knew plenty and plenty about the Cambrian. He was an expert on the Cambrian,
he published many papers. And when you see this little Marrella, its only about acentimeter in length, you get out your hand lens, and you suddenly see that this is, you
know, it shouldnt be there. This is soft-bodied effectively. And Im sure he realized
in seconds what it meant. He must have.
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17. Narration
In the summer of 1910, Walcott found a fossiliferous band in the ridge. After blasting
a quarry, the geologist and his family unearthed thousands of exquisitely preservedspecimens from soft-bodied animals previously unknown to science.
He called the site the Burgess Shale.
18. Simon Conway Morris
There in Burgess Shale (especially the lower level, which Walcott first exploited), thepreservation is miraculous. Its astonishing. We find trilobites of course, but we find
many, many other sorts of arthropods, almost none of which are ever found in a
typical Cambrian assemblage. So we can treat them effectively as being soft-bodied.They have almost no chance of being fossilized in normal circumstances.
19. Narration
Geologists believe that the animals of the Burgess Shale were buried quickly and alive
by an avalanche of sediment that created an air-tight tomb and prevented the decay of
soft body parts like eyes, legs, and internal organs.
20. Simon Conway Morris
Now, in the animal Marrella, very often there is sort of what we call a dark stain. AndI find this very intriguing because that dark stain evidently is the body contents
oozing out. So in other words the animal is beginning to decay, and then something
stops it.
On many of the arthropods we have the most delicate branches, and you can see every
single fine hair along them. Quite astonishing. Many antennae going out like that.
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21. Simon Conway Morris
In particular instances, we have some worms, so we can see the outside of the body.
We can see various things at the front, which enable the worm to burrow through the
sediment. But then you look at the animal itself and you can see this sinuousreflective line, and of course you say--oh, thats the gut. Thats the alimentary canal.
And then in certain cases you actually look at one part of the alimentary canal and you
can actually see food inside it. Shellfish which its swallowed.
It is a remarkable insight into a fossil youd never expect to be fossilized.
22. Narration
The Burgess Shale was once part of a massive reef in the Pacific Ocean-a haven for a
menagerie of life that thrived at the edge of what is now the North American
continent.
Throughout long periods of geologic upheaval, tectonic forces elevated these rocks,
and the fossils they bear, more than 7000 feet above sea level.
Here, the basic body plans of major animal groups that still exist today (and many
others, now extinct), made their first appearance in the fossil record so suddenly that
biologist Richard Dawkins noted: it is as though they were just planted there, withoutany evolutionary history.
These fossils gave science its first detailed look at the biology of the Cambrian seas.
With computer animation, we can now bring that world to life.
23. Narration
Like something out of science fiction, Opabinia was a creature so bizarre it still eludesclassification. While its five eyes watched for predators, the animal captured its prey
with a grasping claw.
First described in 1899 (from a fossil found on Mt. Stephen), Wiwaxia has alsopuzzled scientists.
This mysterious Cambrian animal was covered with overlapping scales and may havefed by scraping microscopic particles off the sea floor.
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27. Jonathan Wells
He would have a branching tree pattern. And for a long time you would only have
that one species, and then it would eventually branch into two species, and then more
species, and different families, and orders, and classes.
And in Darwins thinking, given enough time, those differences accumulate,
especially under natural selection, if the environment changes. Those differences
accumulate to the point where a thousand or a million generations from now yourgreat, great, great, great grandchildren will be a different species .
28. Paul Nelson
So, it is both logically and almost aesthetically a unifying picture, a unifying image,
that pulls together the whole of life on earth. And for many biologists, that kind ofunification is very important.
29. Narration
Common descent and natural selection became the twin pillars of modern biology and
Darwins branching tree of life, its foremost icon.
Yet, despite the clarity and detail of his argument, Darwin acknowledged a problem
that defied explanation: the Cambrian fossil record
30. Darwin character voice
The distinctness of specific forms, and their not being blended together byinnumerable transitional links, is a very obvious difficulty.
I allude to the manner in which species belonging to several of the main divisions ofthe animal kingdom suddenly appear in the lowest known fossiliferous rocks.
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31. Paul Nelson
When Darwin was writing the Origin of Species, it was well known at the time that the
first fossils of animals appeared suddenly without precursors in the geological record.
So there was a deep conflict between what his theory told him to expect to find(namely an abundance of transitional forms going back to that common ancestor for
the animals) versus what was there in the fossil record.
32. Narration
Darwin knew that if his theory was true, the older rock strata directly beneath the
Cambrian layer, should reveal a progression of fossils connecting simple earlier forms
to complex animals (like trilobites), through a trail of incremental steps and failedbiological experiments.
Such evidence would document the trial and error process of natural selection.
33. Paul Nelson
But Darwin says in the Origin, Where are these transitional forms? Theyre not
there in the fossil record. What we see instead are fully formed, discrete groups.Now, thats a world-class puzzle for someone like Darwin
34. Simon Conway Morris
And so its very, very striking, and one can see why Charles Darwin was so puzzled
by the Cambrian explosion because he had enough knowledge even at the time torealize that deep in the earths history you just didnt find the animals.
35. Darwin character voice
If my theory be true, it is indisputable that before the lowest Cambrian stratum was
deposited, long periods elapsed and during these periods of time, the world swarmedwith living creatures.
To the question of why we do not find rich fossiliferous deposits belonging to these
assumed earlier periods prior to the Cambrian, I can give no satisfactory answer.
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36. Stephen Meyer
Darwin was deeply troubled by the Cambrian explosion. He called it an inexplicable
mystery. But he wasnt about to abandon his theory and, instead, proposed that the
animals just looked like they appeared suddenly because he thought that the fossilrecord was incomplete.
37. Darwin voice
I look at the natural geological record, as a history of the world imperfectly kept, and
written in a changing dialect
Of this history we possess the last volume alone, relating only to two or three
countries. Of this volume, only here and there a short chapter has been preserved; and
of each page, only here and there a few lines.
38. Paul Nelson
So Darwin argued, well, perhaps paleontological discovery-digging through the
rocks-needed more time. That the transitions were out there. That not enough
collecting had occurred. Not enough sampling, if you will, of the fossil record on
earth. And, given time, those transitions would turn up
39. Narration
Three decades after Darwins death, Charles Walcotts historic work in the Canadian
Rockies did nothing to fill the gaps in the tree of life or the fossil record.
Walcott uncovered the remains of Cambrian animals unknown to Darwin. And each
demanded its own unique progression of evolutionary ancestorsa trail of evidence
that did not exist in the Burgess Shale.
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40. Paul Nelson
Walcott realized that the Cambrian explosion of life was an even bigger problem than
Darwin imagined. So, in an attempt to defend evolution, he reached back to Darwins
explanation of an incomplete fossil record.
41. Stephen Meyer
Like Darwin, Walcott thought that the Cambrian explosion was an illusion. He was
convinced that the fossils were there. They were just inaccessible to scientific
discovery. And he expected that they would eventually be found buried someplacedeep beneath the oceans.
42. Narration
For decades, Walcotts hypothesis was widely accepted, but untestable. However,later in the 20th century, new technologies led to empirical conclusions.
43. Stephen Meyer
Once the oil companies started to drill offshore, they brought up what are called drillcores. And inside the cores were hunks of sedimentary rock, and some of the rocks
contained fossils. But none of them were made by animals that lived before theCambrian explosion.
44. Narration
Since the 1960s, scientists have also used radioactive minerals, and evidence of
changes in the earths magnetic field, to analyze and date undersea sediments.From extensive surveys, they have created this digital map that defines the age of theseafloor.
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50. James Valentine
In the late Precambrian and at the Cambrian boundary, were seeing the rise of larger
organisms that had fluid skeletons and strong muscles and they could burrow and they
could crawl around. And as time goes by, we begin to see on the ancient sea floorsediments, trails, little squiggles where a small worm was crawling along. They look like
squiggles left by little tiny worms today. So from near 600 million years to 543 millionyears (more or less 50 or 60 million years), what we mostly see, as far as living kinds
of animals, are these little squiggles.
51. Narration
There is also evidence that near the end of the Precambrian, the oceans were inhabited
by jellyfish, sponges, and the mysterious Ediacaran fauna
52. Simon Conway Morris
If you go to immediately before the Cambrian, then actually you find something
extremely puzzling because you get large organisms, large fossils, and these are calledthe Ediacaran assemblages. And they have been one of the great headaches for
paleobiology, and also for evolutionary biology. Why? Well, because basically some
look like animals. But other ones dont look like animals at all.
53. Paul Nelson
Some of them look like air mattresses, quilted air mattresses. Others look like fronds.
Theyre not plants, but they kind of have that appearance.
54. Simon Conway Morris
So these Ediacaran assemblages are bag-like. They are what we call sessile. Most of
them didnt move, or if they did they probably moved pretty slowly. It looks a rathersleepy, a rather dozy world.
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55. Narration
Whether the Ediacarans were actually animals or plants is still uncertain. But late in
the Precambrian, they disappeared from the earth. Then, long after their extinction,everything changed in a geological instant.
In a spectacular burst of creativity, the basic blueprints for most of the animalkingdom exploded into being. And for the first time, biologically complex structures
like compound eyes, spinal cords, articulated limbs and skeletons appeared on earth .
To understand the speed of the Cambrian Explosion, imagine the history of lifecompressed into a single day.
56. Jonathan Wells
If we imagine the whole history of life on Earth taking place at one 24-hour period
(the current standard estimates for the origin of life put it at about 3.8 billion yearsago), lets say, four billion. So if we then start the clock-our 24 hour clock
six hours, nothing but these simple single celled organisms appear. The same sort
that we saw in the beginning.
12 hours, same thing. 18 hours, same thing.
Three-quarters of the day has passed and all we have are these simple single celled
organisms.
Then at about the 21sthour, in the space of about two minutes boom! Most of the
major animal forms appear, in the form that they currently have in the present. Andmany of them persist to the present. And we have them with us today.
Less than two minutes out of a 24-hour period. Thats how sudden the CambrianExplosion was.
57. Narration
Since Darwin, excavations on every continent have revealed the magnitude of theexplosion of life-an event that was clearly global in scope.
Most recently, several discoveries in southern China have fascinated science and
deepened the Cambrian mystery.
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58. Narration
In 1984, one of the most important finds in the history of paleontology was madeoutside a small town in Chinas Yunnan province.
While surveying this mountain near Chengjiang, Hou Xian-Guang unearthed
Cambrian fossils older, more diverse, and better preserved than any ever discovered.The condition of the Chengjiang fossils was so remarkable Hou said, it appeared as if
the animals were alive on the wet surface of the mudstone.
59. Simon Conway Morris
The fossils theyve collected are stunning, really beautiful to look at.
60. James Valentine
Theyre brightly colored, stained with iron and probably other kinds of minerals so
theyre kind of golden looking or kind of reddish and they really stand out from the
rather tan colored background of the rocks. And theyre just beautiful. Soaesthetically, theyre wonderful.
61. Jonathan Wells
Many of them are soft-bodied. No hard parts, no skeletons, no shells, just soft bodied,
and yet theyre exquisitely preserved. So you can see the Cambrian explosion in greaterdetail than you can anywhere else in the world
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62. Narration
In the early 1990s, reports of the Chinese fossils were released to the rest of
the world. At the University of San Francisco, marine biologist Paul Chien
followed the news.
63. Paul Chien
What drew my attention was, in fact, a couple of articles published in Peoples
Daily. The official paper for the communist party in China announced that the
Chengjiang fossils drew the attention of scientists worldwide.
Peoples Dailyreported that this find actually challenges the theory of
Darwins evolution.
And then, towards the end of 95, Time Magazine(on December 4th),
had this
front cover story about animal big bang, which talked about Chinese great leapforward in science. That really solidified my interest. I said this is something
really big. I want to get to the bottom of this. One day I will stand in front of
the fossil site myself and find out whats going on.
64. Narration
Since 1996, Paul Chien has made several trips to southern China to conduct hisown investigations.
65. Paul Chien
When you talk about the Cambrian explosion a lot of people find it fascinating
and so forth. But when you get into the topic, generally there are two
reactions-people who love it and people who kind of avoid it.
The Cambrian explosion does challenge the traditional idea of gradual
evolution of animals, because they all seem to appear all of a sudden and the
problem is, how do they explain it?
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66. Narration
Paleontologists have determined that the Chinese fossils were older than those
excavated at the Burgess Shale. Yet, anatomically, they were often even morecomplex.
This discovery also confirmed that previous estimates of an explosion lasting20-40 million years were much too long.
67. Paul Chien
The time period that we figured it took the animals to be established in the
ocean in those days took probably ten million, five million years. So this istruly an explosive event in the scientific terms.
What we are seeing is a quantum jump. And this quantum jump has no
explanation
68. Jonathan Wells
The Cambrian explosion was so short that it is below the resolution of the
fossil record. It could have happened overnight. So, we dont know the
duration of the Cambrian explosion. We just know that it was very, very fast.
69. Paul Nelson
As the interval of the Cambrian explosion is compressed (in other words, asthe time available shrinks), the challenge to evolutionary theory grows because
the differences in form that have to be constructed very rapidly are much more
dramatic. Its going to pose a real and, I think, fundamental challenge to
evolutionary mechanisms.
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70. Paul Chien
From what I saw, the Chinese scientific community, as a whole, seem to be rather
progressive about this. They are convinced by the evidence that the Cambrian
explosion is real. And they see it as a challenge to Darwinian theory. They are honestabout this. Therefore, they are thinking about how to explain this outside of the
Darwinian thoughts.
71. Narration
The Chengjaing fossils provide the most inclusive picture of the Cambrian explosion
yet documented. And directly beneath them (in Precambrian shales), another chapter
in the history of life is written in the rocks.
72. Steve Meyer
Theres another amazing find thats been made in China. Paleobiologists havediscovered litte, tiny microscopic sponge embryos in the layers of rock just beneath
the layer that documents the Cambrian explosion.
73. Narration
These embryos were soft-bodied animals, some fossilized 60 million years beforethe
Cambrian explosion.
74. James Valentine
There are eggs and embryos which are preserved in thin crusts of mineralized material(a phosphatic material on ancient sea floors) which suggest that the chemistry of the
sea water in those days was somewhat different than it is today.
Because this method of preserving fossils disappears during the Cambrian and its not
around today. So were lucky that we have these thin crusts with little tiny fossils inthem
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75. Stephen Meyer
This is highly significant because one of the most popular explanations for the missing
Precambrian fossils is that the Precambrian animals were too soft and too small to
have been preserved.
76. Narration
Since 1999, Paul Chien has studied fossil embryos and helped develop techniques to
analyze their structure.
77. Paul Chien
By treating them with acid you can actually remove the rock and isolate the embryos.
And then youve got a round pebble-like or sand grain like samples. And then welooked through some tiny little ones, and larger ones up to one millimeter in size. And
we found about the range between 500 and 800 micrometers,we have mostly sponges.
And then I stopped breaking up these balls and tried to start looking inside. And withthe help of the electron microscope, I was able to see the detailed sub-cell structure
within these embryos.
78. Narration
Chiens work on these fragile remnants of Precambrian life raises an important
question.
79. Stephen Meyer
If these lower strata can preserve an embryo. If they can preserve a soft microscopicembryo-then why couldnt they have preserved the larger ancestral forms that
supposedly evolved into the Cambrian animals?
In other words, if you can preserve something as fragile as an embryo, why couldnt
you, in the same strata of rock, preserve the immediate ancestor of a hard shelled
trilobite?
80. Jonathan Wells
So, the idea that the fossil record is too damaged to provide us with at least a general
picture-that idea just doesnt wash.
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81. Narration
During the past 150 years, fossil hunters have searched the earth for the manytransitional links Darwins theory requires.
82. Paul Nelson
If I sent you on a treasure hunt and said, what I really want it this, youre going out
and look for this, whatever it happens to be. Well, if you come at the fossil record
with a Darwinian expectation of an abundance of transitionals, thats whats going toget you a professorship. You find those transitional forms.
So, all over the world in countless outcrops, people have been looking for those formsthat would capture the major transitions in the history of life.
83. Narration
This search has extended from the walls of Grand Canyon to the shores of the Irish
Sea. And as countless specimens have been excavated, one question endures:
How complete is the Cambrian fossil record?
84. Simon Conway Morris
I think the Cambrian fossil record is surprisingly complete, I think it may be more
complete than we realize. The reason for that is for instanceif you look at the
stratigraphy of the worldif I go and collect Cambrian rocks in Wales and findcertain fossils, if I then go to China I dont find the same species, but I find the same
sorts of fossils. If I go into carboniferous rocks, I go to Canada, theyre the same as
what I find in this country. So theres a clear set of faunas and floras which take us
through geological time. The overall framework is falling into position.
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85. Paul Nelson
Theres no question that if you dig and sample more, youre going to find new kinds
of fossils. But, generally speaking, the fossils that we find, fall into groups we already
knew about. When you see that, what I think nature is telling you is youve got apretty good sample of the history of life on earth. The groups that you already
established are the ones that capture the new fossils.
86. Paul Chien
To the paleontologists, the lack of intermediate fossils is well known. Some people stillthink that if you look long and hard enough you will eventually find them.
But I think most of the paleontologists that I have been in contact with, would not
have that hope very high. They simply feel that we have looked long and hard enoughand that they are not there, they are not there.
87. Darwin Character voice
The difficulty of assigning any good reason for the absence of vast piles of strata rich
in fossils beneath the Cambrian system is very great. The case at present must remaininexplicable and may be truly urged as a valid argument against the views here
entertained.
88. Narration
In 1831, three months after his first exposure to Cambrian geology, young CharlesDarwin embarked on an expedition that would influence the development of his theory
of evolution.
As naturalist aboard the HMS Beagle, Darwin sailedto the Galapagos Islands, 600
miles off the coast of Ecuador. For five weeks, Darwin explored this remote island
chain-home to an extraordinary assembly of animals. Here, the idea for his tree of lifewas planted.
According to Darwin, as one form of life morphed into another, new species arose.And, as they gradually branched apart, larger differences in form emerged.
Eventually, evolution produced an even greater level of disparity-the distinct body
plans of new phyla.
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89. Paul Nelson
Phyla are abstract categories that bring together basic features that unite large groups
of animals. So you can think about a phylum as a group of organisms that all share a
basic architecture.
90. Jonathan Wells
Based on the body plan of the animal we divide animals into these major groups.
Theres vertebrates-the backbone and soft bodies outside the bone structure.There are arthropods, which have a hard skeleton on the outside and a soft body on the
inside. These are the insects and the crabs. Theres the echinoderms, which are the
sea urchins and starfish.
91. Paul Chien
Sea stars are different from jellyfish, different from worms and different from crabsand lobsters. So each group has their unique features that make them very different
from the next group.
92. Narration
The stability of these forms in the animals that exemplify the distinct phyla, contradict
Darwins vision of an interconnected tree of life.
93. Paul Nelson
The phyla dont blend, imperceptibly, one into another. Arthropods, for example
didnt evolve from chordates. Mollusks arent the offspring of sponges.
Instead, a phylum is, in effect, as different as it can be from another phylum. So, how
did those differences arise? If one reads The Origin of Species, its clear that Darwinscaught in a bind.
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94. Steve Meyer
Natura non facit saltum. That was Darwins famous Latin phrase which means,
nature takes no sudden leaps. In fact, Darwin went on to say, that if you found
evidence of saltation, of sudden appearance in the fossil record, that would besomething like evidence of special creation.
95. Narration
One of the most striking examples of a sudden leap in nature is evident in the number
and stability of new animal body plans that first appeared during the Cambrianexplosion.
96. Steve Meyer
One of the other remarkable things about the Cambrian explosion is that a hugepercentage of the total number of phyla that have ever existed on earth, all appear
within a very narrow window of time.
97. Paul Nelson
Its a defensible statement, that most of the major animal body plans are present in theCambrian explosion. Thats where they first appear.
98. Paul Nelson
Imagine a graph, if you will, of the appearance, over time, of phyla. In Darwinspicture, youd haveonethen twothen four, perhapsthen eight. A gradually
increasing curve of the number of phyla growing over time.
99. Steve Meyer
What you actually have in the fossil record is a sudden spike in the number of phylathat appear during the Cambrianand then a few that trickle in across the rest of
geologic time
This kind of discontinuity is radically at odds with the Darwinian picture of the history
of life.
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100. Paul Nelson
The pattern we see is the major body plans present at the beginning and that theorganisms that we know today, fall into one or another of those major body plans.
They dont gradually increase over time.
101. Narration
The sudden appearance of animal body plans deepens the Cambrian mystery in
another way. The Darwinian model predicts that as new biological forms evolved(simple to complex), they developed gradually-from the smallest differences in
classification to the largest. Or, from the bottom-up.
102. Jonathan Wells
Darwins idea was that given enough time evolution would lead to new species, new
families, orders, and eventually phyla. And only after millions and millions ofgenerations do you end up with the several dozen phyla that we see around us now
days. That would be the bottom- up pattern predicted by Darwins theory.
103. Paul Nelson
Now, the other picture is top-down. The top-down picture says the primary
differences are original. Theyre there right at the start.
When you find mollusks in the fossil record, or the arthropodsboom, there they are,
with the major differences present, right at the beginning. So the upper levelarchitecture is, top-down, present, right there.
104. Narration
This top-down pattern of biological development can be compared to the
development of human technology.
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105. Stephen Meyer
If you look at any major invention, like the automobile, for example-the basic body
design is set in place from the very beginning.
Youve got four wheels, a chassis, a drive shaft, two axles. There are certain basic
features of all automobiles that have persisted since Ford and Benz got the whole thing
going over a century ago.
106. Narration
In the decades that followed the introduction of the automobiles basic framework,designers and engineers have created thousands of variations on the original theme.
But regardless of differences in size, color, and chassis design, the foundational body
plan remains consistent to its original form.
107. Stephen Meyer
And an interesting thing about the fossil record is that theres a similar top-down
pattern evident in the history of life. The basic body plan of the arthropod phylum hasa segmented torso, jointed legs, and an exoskeleton all of which arose suddenly at the
beginning of the Cambrian explosion. And today, we still see the continuity of thisoriginal plan, this foundational idea, in over a million species of animals.
108. Narration
This top-down pattern looks nothing like the predictions of Darwins theory
109. Jonathan Wells
Darwins theory is that there is a tree of life, where you have one organism diverginginto many other organisms and big differences appearing at the top.
What we really see is, from here up. This does not exist in the fossil record.
If I were to using a botanical illustration it would be a lawn, with separate blades of
grass sprouting independently of each other. And those would be the phyla. Now,
within each phylum there is subsequent diversification. But even there, I dont see the
branches connecting that would make them a tree of life.
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110. Paul Nelson
Darwin was caught in the grip of a deep dilemma. The fossil record showed him onething. His theory told him something else.
He comes to an impasse at this point and he says, "If this pattern holds, it is a genuine
argument against by view." I think 150 years later, we have added a great deal moredetail to the picture, but I think the basic problem is still unsolved.
111. Stephen Meyer
How did these new animal body plans and fundamentally new forms of life come into
existence? This was the mystery Darwin set out to solve. But everything weve
learned in biology over the past 50 years has brought this mystery back with avengeance.
How do you explain the origin of the Cambrian animals seemingly out of nowhere?This isnt just a problem of explaining the absence of evidence in the fossil record.
Its also a problem of explaining everything we know about life, right down to thelevel of molecules and cells.
112. Narration
The biological structure of a Cambrian trilobite was as complex and sophisticated as amodern crab. Its organs included a brain, gut, heart and compound eyes. Each organ
was constructed from specific types of cells. Each cell type was made from dozens ofspecialized protein molecules. And each protein was assembled from a four-letter
chemical code in a section of DNA called a gene.
113. Stephen Meyer
Now, for the evolutionary process to transform a simple Precambrian organism like a
sponge (with 4 or 5 cell types) into a Cambrian trilobite (with at least 10 times asmany different types of cells)thats a huge leap in complexity. And to make thatleap, youd need a vast amount of new genetic information
But, where did this information come from? Thats the central mystery of theCambrian explosion.
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114. Narration
According to Neo-Darwinism, new proteins are constructed by the dual mechanismsof genetic mutations and natural selection. As the genetic instructions for building
proteins are copied, an occasional error can alter their contents. If these accidental
revisions prove beneficial to survival, they are selected or preserved and passed on tofuture generations.
Over eons, these small changes accumulate and new proteins, cell typesand even
Cambrian carnivoresgradually evolve into existence.
115. Stephen Meyer
Richard Dawkins, the famous Oxford evolutionary biologist, has illustrated how the
Darwinian mechanism works using the metaphor he calls climbing Mt. Improbable.
116. Narration
From the front side, the mountain is a sheer cliff that could never be scaled in one
giant leap. For Dawkins, this represents the impossibility of creating a complexanimal, by chance alone. Yet, Dawkins also envisionedan alternative route up the
backside of Mt Improbable. A long, gradually sloping trail of small steps leading all
the way to the summit.
117. Stephen Meyer
According to Dawkins, thats how youd climb the mountain. And thats also howyoud build a Cambrian animal-one small step at a time.
What chance alone cant accomplish in one blind leap, natural selection canaccomplish through the cumulative effect of many small incremental steps.
118. Narration
In theory, each step corresponds to a small unit of biological change-a new gene and
its protein product. But do mutations and natural selection have a reasonable chance of
producing even one protein in the time available? Since 1992, molecular biologist
Doug Axe has examined this question.
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119. Doug Axe
Theres a story thats being told and theres an appeal in the case of Darwinism to
random mutation and natural selection as being, in vague terms, the mechanism. But if
you look at the detail, what kind of mutation can accomplish these transitions?
And there, its important to realize that the one area where we can really nail this
down is at the single protein level where you can actually measure it. And if you look
at protein structures, to get a substantially new protein fold is prohibitively difficult.
120. Narration
Each of the thousands of different proteins in nature is actually a chain made from aspecific combination of 20 different amino acids. The sequential order of thesechemical building blocks is crucial, for if they are arranged correctly, the chain folds
into a functioning three-dimensional molecule. But if the amino acids are incorrectly
assembled, no protein will form.
If proteins are indeed rare among the possible sequences of amino acids, what are theodds that mutations would stumble upon a functional combination of chemicals from
the vast number of alternatives?
To find out, Axe randomly altered the structure of an enzyme protein comprised of
150 amino acids.
121. Stephen Meyer
Youve got a protein 150 amino acids long, then youve got 20 to the 150th
power ofpossible ways of arranging the amino acids. Out of all those possibilities, how many
are functional and how many are gibberish?
122. Doug Axe
If you do the experiments and you analyze how much information is required to get anew protein fold, its just far beyond what you can get by random mutation and natural
selection.
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123. Narration
How far beyond? Axe published his findings in The Journal of Molecular Biology.
He determined that among all of the possible amino acid combinations, the probability
of generating just one short protein by mutation is roughly 1 in 10 to the 74th
power.
Or, one chance in a hundred trillion trillion trillion trillion trillion trillion
124. Stephen Meyer
To put that in context, there are only 10 to the 65 atoms in the entire galaxy. So tobuild a new functional protein, by selection and mutation (within the time allowed for
the Cambrian explosion), what youre essentially having to do is equivalent to a
blindfolded man looking throughout the entire galaxy for one marked atom.
So what were talking about is searching for a tiny, tiny needle in an enormoushaystack. And having a very limited time to search.
125. Doug Axe
So on the question of something like the Cambrian explosion, there does not appear to
be any way that unguided random mutations can accomplish what needs to be
accomplished to explain new functional proteins.
And certainly by extension, wherever in the history of life you would need to havemultiple new protein folds the probabilities multiply. So theres no reason to think that
this is plausible.
126. Narration
But the inability of random mutations to generate new genes and proteins is only part
of the problem. For, the origin of Cambrian body plans demanded more than newgenetic information.
127. Richard Sternberg
A lot of the information for specifying an Anomalocaris, a Trilobite, what have you,
does not reside at the DNA level.
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128. Jonathan Wells
The body plan, as far as we know, is not in the DNA.
129. Narration
While DNA carries the instructions to manufacture proteins, it cannot alone, assemble
them into cell types. Or arrange cell types into new tissues and organs. Or tissues andorgans into body plans.
Instead, the formation of body plans ultimately requires another level of information
stored somewhere in the three- dimensional structure of the egg cell and the embryo
Instructions that direct the development of complex animals from fertilized eggs.
With computer animation, we can observe this intricate process.
130. Narration
As an egg cell begins to divide and differentiate, a network of biological commandsorchestrates the development of an arthropod.
After several stages of division, dozens of new cells align against the outer membraneof the egg. And then, cued by a chemical signal, they start their migration toward
targeted areas in the embryo where they will gather and develop into a mature
organism.
131. Narration
The cells steadily increase their numbers and align, like members of a marching band,
into patterns that will form the tissues and organs, head and legs of the growingembryo.
132. Paul Nelson
That happens by a process of cell specification and differentiation where cells arecommitted, irreversibly, to performing particular roles. Youre going to give them
different jobs to do. Youre going to be part of the locomotary system of thisorganism. Youll be an eye, youll be a gut, and so forth. To me thats an absolutely
astonishing process, but it works. And what it builds you is different kinds of
organisms depending on the instruction set thats provided
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133. Richard Sternberg
So there is an organismal blueprint-an ultimate point that the embryo hones in on, and
is attracted to, and eventually embodies.
134. Jonathan Wells
That foresight, that preordained outcome, is built into the embryo
135. Richard Sternberg
When you talk about these early developmental sequences in Anomalocaris, and
Opabinia, or what have you, youre talking about information in the broad sense,codes, specifications, entailments, implicationsthat are orders of magnitudebeyond
anything we can currently conceive. Its so off scale that youve left that line of
impossible by chance a long time ago.
136. Narration
The volume and complexity of information that controls the development of a body
plan is staggering. And its location in the cell stands as perhaps the ultimate
challenge to the neo-Darwinian scenario of random mutation and natural selection.
137. Steve Meyer
We know that much of this higher level information required for building new tissues
and organs and body plans isnt found in DNA. That means that you can mutate DNAindefinitely without respect to probabilistic limits, without respects to time and
number of trials, and youre never going to get the kind of form and structure you need
to build a new organism.
DNA is simply the wrong tool for the job and no amount of time is going to overcome
that limitation. That has a really devastating implication for the Neo-Darwinian
mechanism.
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138. Narration
If the Darwinian mechanism cannot explain the origin of the information necessary to
produce the Cambrian animals-is there any other cause that can?For more than 20 years, Stephen Meyer has explored this fundamental mystery.
In August 2004, Meyer published several of his conclusions in a peer-reviewed journal
affiliated with the Smithsonian Institution. His essay triggered a firestorm ofcontroversy that jeopardized the career of the journals editor, evolutionary biologist
Richard Sternberg. But, why did a technical paper on the origin of animal body plansevoke such heated response?
139. Stephen Meyer
For many people, the problem with the paper was simply my conclusion. I not only
argued that the Darwinian mechanism could not explain the origin of the new form
and information that arises in the Cambrianbut, I also argued that there were critical
features of that explosion that pointed to the reality of a designing intelligence in thehistory of life.
140. Narration
Since his years as a graduate student at Cambridge University, Meyer has worked todevelop a scientific case for intelligent design. A case based on a standard method of
reasoning used by both Darwin and the famed 19th
century geologist, Charles Lyell.
Lyell insisted that the best explanation for an event in the remote past was a cause,known from our experience, to produce it. A presently acting cause-one now in
operation
141. Stephen Meyer
The present is the key to the past. That was Lyells dictum. Its standard historical
scientific methodology. If youre trying to reconstruct what happened in the remote
past we should let our present experience of cause and effect guide our search for thebest explanation.
142. Narration
This reasoning helped focus Meyers conclusions about the origin of information.
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143. Stephen Meyer
The light came on for me because I realized its not that hard. What youre looking
for are causes, which are known to produce the kinds of effects youre trying to
explain.
And I asked myself the question: what is the cause now in operation that produces new
information-whether its digital code, or whether its hierarchical information in theform of a blueprint? Where does that kind of information come from?
Well, we know from our experiencefrom uniform and repeated experience (which isthe basis for all scientific reasoning about the past)-that information always comes
from an intelligent source.
And so when we find information in the Cambrian animals, when we realize that large
infusions of new information are required to build those animals, the most natural
thing, the most logical thing to conclude is that those animals owe their origin to anintelligent source.
That the information required to build them, in turn, must have come from anintelligence.
As Ive reflected on this over the years, Ive realized that the same reasoning thatapplies to the origin of biological information, also applies to the origin of the other
key features of the Cambrian explosion.
144. Narration
The sudden top-down appearance of the phyla during the Cambrian explosion defies
the simple-to-complexpattern of development that Darwin predicted.
145. Paul Nelson.
In Darwins picture, youd have little differences accumulating to big differences. Thetop-down picture turns that on its head.
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146. Stephen Meyer
You find first you get new phyla, and then you have some variations on those themes
over time. But the new form, the big differences appear right from the beginning in
the fossil record.
Now, if you consider the possibility of design, you realize that that pattern makes
perfect sense because we see in our own history of technology the same pattern of top-
down appearance in new forms.
147. Douglas Axe
Youre always working from your high level objective to your details in order to
accomplish the high level objective.
148. Paul Nelson
Only intelligence can visualize a complex end point and bring together everything
thats needed to actualize that end point.
149. Narration
The body designs evident in the Cambrian animals have continued to appear indifferent species throughout the history of life. Yet though these species share
common body plans, they are not connected by a continuous line of intermediatematerial forms.
150. Steve Meyer
The continuity that explains that consistency of form through time is the continuity ofan idea. And so when we see in the fossil record the same basic idea popping up overand over again, that suggests that a mind has played a role in the origin of that form, of
that body plan organization.
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151. Narration
Designed systems also display another distinctive feature: they are comprised of a
network of complex, and precisely organized, component parts.
152. Douglas Axe
You could speak of these in terms of a nested hierarchy. You have the very high levelparameters that specify the whole project goal. Below that you have layers and layers
of more detailed parameters that are needed in order to complete the whole project.
153. Narration
As an example, resistors, capacitors, and transistors are each made from specifically
arranged materials. These components are then assembled to form integrated circuits.
Circuits are arranged to build computersthat are then arranged into networks ofcomputers.
154. Stephen Meyer
So at each level there is a specificity of arrangement thats provided in turn by the
intelligent designer, the engineer that keeps the whole system working. Well, what
you have in biology is something very similar.
155. Narration
In living systems, genes code for proteinswhich are organized to form distinctive
cell typeswhich are arranged to form tissues and organswhich are assembled intobody plansincluding the plans that arose during the Cambrian explosion.
156. Stephen Meyer
We know of only one cause in the entire universe that can produce that kind of
hierarchical arrangement of form, and structure and information, and that cause is
intelligence. This is the kind of thing that minds do, but natural undirected processes
dont.
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157. Paul Nelson
Evolution works very slowly as Darwin saw it. With lots of failed experiments along
the way and one would expect, that over millions of years, as sediment was beingdeposited, that you would capture some of those experiments, some of those linking
groups leading to the trilobites that he knew all about
158. Stephen Meyer
And so the absence of those forms is profoundly mysterious. But from the standpoint of
intelligent design its not mysterious at all because we know that intelligent agents canbring things into existence that didnt exist before, because they had an idea. They had a
blueprint in their minds that they realized in their creative activity.
So, theres no need to tinker through millions of years of evolutionary history if you can
actualize a plan at a discrete moment in time. And thats exactly what appears to have occurredin the Cambrian explosion.
159. Darwin Character voice
If numerous species, belonging to the same genera or families have really started into
life all at once, the fact would be fatal to the theory of descent with slow modificationthrough natural selection.
160. Narration
No aspect of the natural world troubled Charles Darwin more than the Cambrian fossil
record and the explosion of life it revealed. Today, many of the details of this
remarkable chapter in the history of life still await resolution.
Yet modern paleontology, genetics, and embryology have cast new light upon the
Cambrian mystery and the origin of complex life on Earth.
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161. Douglas Axe
If you have very different forms of life that appear in a very short, and a very brief
time period with respect to the earths history, it certainly has the appearance that
design problems were solved, and that they were solved elegantly, and that they were
solved in very many instances.
162. Richard Sternberg
When these forms appeared it wasnt just one or two rickety, hanging on the edge
forms. It was a panoply, a manifold of different body types.
It does have an explanation, if you regard in addition to matter and energy in the
universe, information as being just as important, if not more important. And that iswhere I think intelligent design theory comes into play.
163. Paul Nelson
I think, to build an animal, the kind of process the evidence requires is a process thatcan look into the future and bring everything together, to actualize something like a
trilobite, or a chordate, or a mollusk, or the other different forms that we see in the
Cambrian explosion.
Its going to be a process that has foresight. Its going to be a process that can
visualize complexity. Its going to be a process indistinguishable from intelligence.Thats not natural selection. Thats design.
164. Steve Meyer
The postulation of intelligent design not only helps to resolve a longstanding scientificmystery, but it also speaks to a larger question
Because what we see in the origin of complex life on earth is not evidence of just anundirected process. Instead we see evidence that life was designed, that life was
plannedthat it was intended.