More Problems with TalkOrigins' Response on the Cambrian Explosion - Evolution News & Views

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More Problems with TalkOrigins' Response on the Cambrian Explosion

A few weeks ago, Jonathan M. had an excellent article on ENV about the failure of the TalkOrigins (TO) Archive to defend Darwinian explanations of the Cambrian explosion. As he explained:

A correspondent recently referred me to an article in the TalkOrigins Archive responding to the argument that "Complex life forms appear suddenly in the Cambrian explosion, with no ancestral fossils." TalkOrigins is a popular online resource that collects attempted answers to some often-heard challenges to Darwinian evolutionary theory. The article offers seven responses to the contention that the Cambrian explosion, which occurred some 530 million years ago, represents a significant difficulty for the neo-Darwinian view on how animal body plans evolved.
I too received an e-mail (separately) a couple months ago on this same TO page and wrote a response. So now that Jonathan M. has broached the issue on ENV, I thought I'd share part of my commentary here as well. (I'll borrow Jonathan M's summaries of the seven points on the TO page.)

Point #1: Complex life preceded the Cambrian.

The TO page asserts, "The Cambrian explosion was the seemingly sudden appearance of a variety of complex animals about 540 million years ago (Mya), but it was not the origin of complex life." That's true--all life is complex and the first bacteria, which appear some 3.5 billion years ago, represents an incredible jump in the complexity of life! But the TO page's point is that Precambrian life was complex and the "Cambrian explosion" isn't so impressive. It then lists a few examples of Precambrian fossils, such as stromatolites, and other fossil microorganisms. As we explain here, these ancient microfossils most likely represent bacteria, not the kind of multicellular precursors necessary to explain the evolution of the Cambrian fauna.

A relatively complete response on this issue is found in Question 2 of the Darwin's Dilemma FAQ, which shows why many Precambrian fossils don't explain the origin of the Cambrian fauna. The FAQ states:

Precambrian fossils exist; this has been known for many decades, from fossil localities around the world. But no ID proponent has ever argued that there are no Precambrian fossils. Rather, ID proponents observe that there are no clear evolutionary precursors to the Cambrian fauna, where nearly all of the major living animal phyla appear in an abrupt fashion without any evolutionary antecedents. That the precursors to the Cambrian groups are indeed missing from the record is widely accepted among paleontologists; thus, this is not the controversial aspect of the ID position. About the missing precursors at the base of the tree of the animal phyla, Valentine notes:
...many of the branches, large as well as small, are cryptogenetic (cannot be traced into ancestors). Some of these gaps are surely caused by the incompleteness of the fossil record..., but that cannot be the sole explanation for the cryptogenetic nature of some families, many invertebrate orders, all invertebrate classes, and all metazoan phyla.1
Charles Marshall concurs:
While the fossil record of the well-skeletonized animal phyla is pretty good, we have virtually no fossils that are unambiguously assignable to the most basal stem groups [putative ancestors] of these phyla, those first branches that lie between the last common ancestor of all bilaterians and the last common ancestor of the living representatives of each of the phyla....their absence is striking. Where are they?2
To be clear: Valentine and Marshall, leading paleontologists, oppose ID theory.

By contrast, most ID theorists argue that the ancestral fossils are missing because they never existed. The best explanation of this abrupt bioinformational explosion of new body plans, they argue, is intelligent design. This is the controversial aspect of the ID position on the Cambrian explosion.

But let's turn to Schopf's PNAS paper, which discusses some of the known Precambrian fossils. Contrary to what his title suggests, however, these fossils comprise bacterial and other unicellular fossils that do not provide the "solution to Darwin's dilemma." For example, fossils cited by Schopf include:

  • Eozoon canadense, which was found to be not a fossil but a rock produced by metamorphism. Early evolutionary biologists wrongly presumed it was a fossil because they so badly wanted to solve "Darwin's dilemma."
  • Cryptozoon, which is thought to be a stromatolite -- a bacterial mat. At best, these stromatolites only show bacteria and are not true multicellular fossils that would have been directly ancestral to the Cambrian fauna. Like the prior example, this turned out to be a case where, according to Schopf, "Mineralic, purely inorganic objects had been misinterpreted as fossil." Thus faulty evolutionary presumptions about Precambrian fossils led to wrong conclusions about these fossils.

  • Chuaria, which is a single-celled algae, originally wrongly thought to be a shelly invertebrate due to more misguided attempts to solve "Darwin's dilemma."
  • Barghoorn Gunflint microfossils, which again comprise bacterial stromatolites that do not serve as precursors to the Cambrian fauna.
  • Bitter Springs Chert, which again are microbe fossils, not clear evolutionary precursors to the Cambrian fauna.
  • Saucer-sized organisms at Ediacara, also called the Ediacaran fauna, which are enigmatic fossils generally not thought to be ancestral to the Cambrian fauna.

Regarding this last example, the Ediacaran fauna are often cited by those who discuss Precambrian fossils. But these fossils do not solve "Darwin's dilemma" because they are not thought to be ancestral to the modern phyla that appear explosively in the Cambrian. (In fact, the documentary Darwin's Dilemma extensively discusses the Ediacaran fauna and how they do NOT explain the Cambrian explosion.) As evolutionary paleontologist Peter Ward writes:

[L]ater study cast doubt on the affinity between these ancient remains preserved in sandstones and living creatures of today; the great German paleontologist A. Seilacher, of Tübingen University, has even gone so far as to suggest that the Ediacaran fauna has no relationship whatsoever with any currently living creatures. In this view, the Ediacaran fauna was completely annihilated before the start of the Cambrian fauna.3
In fact, Seilacher's view is shared by various modern evolutionary scientists. Cooper & Fortey (1998) show in Figure 1 of their paper that the Ediacaran (called "Vendobionta") fauna are not ancestral to the Cambrian fauna, and they write:
The beginning of the Cambrian period, some 545 million years ago, saw the sudden appearance in the fossil record of almost all the main types of animals (phyla) that still dominate the biota today. To be sure, there are fossils in older strata, but they are either very small (such as bacteria and algae), or their relationships to the living fauna are highly contentious, as is the case with the famous soft-bodied fossils from the late Precambrian Pound Quartzite, Ediacara, South Australia.4
Likewise, Andrew Knoll and Sean Carroll observe that "It is genuinely difficult to map the characters of Ediacaran fossils onto the body plans of living invertebrates" and thus evidence of these fossils being precursors to Cambrian fauna "remains equivocal."5 A Blackwell Scientific invertebrate biology textbook concurs that the Ediacaran fauna do not solve Darwin's dilemma:
Whether they were, in fact, early members of any phyla still living today and possible ancestral forms, or were members of phyla long since extinct, is a question of considerable current debate. At any rate, they shed little light on the question of which phyla were ancestral to other phyla, or if indeed, animals have a common ancestry.6
Finally, prominent paleontologists Valentine, Erwin, and Jablonski are hesitant to claim these Ediacaran fossils bear any ancestral relation to Cambrian fauna, stating that "the relations of any of these fossils to Cambrian bilaterians remains uncertain and awaits further collecting and critical analysis."7 Most evolutionary scientists thus do not believe that the Ediacaran fossils solve "Darwin's dilemma."

Point 2: Transitional fossils exist.

The TO page asserts, "There are transitional fossils within the Cambrian explosion fossils. For example, there are lobopods (basically worms with legs) which are intermediate between arthropods and worms."

TO's primary evidence backing this claim is the fact that lobopods have legs (kind of) like arthropods, and are segmented, but also are wormlike. As for their affinity to worms, if they are related to worms, then it stands to reason they would be most closely related to annelid worms, which are the segmented worm phyla. Unfortunately, both the fossil and molecular evidence now contradicts the claim that lobopods are "intermediate" between arthropods and worms, such as annelids.

First, let's look at the fossil record. A 2001 paper in Science by Richard Fortey titled, "The Cambrian Explosion Exploded?," contains a diagram showing how abruptly arthropods and onychophorans (modern organisms that are a type of lobopod) appear in the fossil record. I don't have the rights to show the diagram, but it basically shows that lobopods (represented as onychophorans) and arthropods appear at more-or-less exactly the same time in the fossil record, with the Precambrian period representing what the paper calls "hidden history."

If lobopods and arthropods appear essentially at precisely the same time with their evolutionary history "hidden," this ordering does not lend much support to the view that lobopods were precursors to arthropods, much less intermediate between them and anything else. Consider also how the paper itself explains how the fossil record does very little to document the origin of arthropods:

Crustacea are one of the great groups of living arthropods, embracing crabs, shrimps, lobsters, and slaters. Hitherto, the oldest undoubted crustaceans came from the late Cambrian "orsten" of southern Sweden (the alleged crustacean Canadaspis, from the mid-Cambrian Burgess Shale, British Columbia, has proved controversial). This allowed some 40 million years from the base of the Cambrian to generate an ancestral crustacean from some primitive arthropod--time enough, indeed. But if crustaceans were already present in the early Cambrian, this pushes back in time the necessary steps in the evolutionary tree of arthropods that led to the crustacean design. It then becomes perfectly plausible that this early radiation happened in the late Precambrian. This squares with previous critiques, which noted that in the early Cambrian, some arthropods--especially the ubiquitous trilobites--had already differentiated into different kinds with separate geographical distributions. This differential evolution and dispersal, too, must have required a previous history of the group for which there is no fossil record. Furthermore, cladistic analyses of arthropod phylogeny revealed that trilobites, like eucrustaceans, are fairly advanced "twigs" on the arthropod tree (see the figure). Trilobite-like trace fossils extend to the base of the Cambrian in Newfoundland, and it would be easy to conclude that appropriate trace makers must have appeared still earlier, in the late Precambrian. But fossils of these alleged ancestral arthropods are lacking.8
In essence, we don't have fossil ancestors documenting the evolution of arthropod groups in the Precambrian. We have lobopods (something like modern onycophorans) in the Cambrian explosion, and we have major arthropod groups, but there's no fossil evidence of a lineage showing lobopods evolving into arthropods, or linking them to annelid worms. The evolution of these phyla is said to be "hidden history." Not exactly a compelling argument for evolution.

Now let's consider the molecular data.

If lobopods are closely related to annelid worms and arthropods, then we'd expect annelid worms, arthropods and onychophorans to nest closely in molecular trees. But that isn't what we find. In fact, the molecular data is a mess and often conflicts with the morphological data when you try to construct phylogenetic trees for the major animal phyla.

One paper states: "Prior to 1997, the prevalent view of arthropod relationships linked them, via the onychophorans, to the annelid worms."9 So what happened in 1997? Well, that was when scientists started sequencing the DNA of these phyla and found that annelid worms are NOT molecularly close to arthropods. Today, the idea that lobopods should serve as a "intermediate" between arthropods and annelid worms no longer make sense, because the molecular data suggests they aren't closely related.10 The TalkOrigins page is outdated because modern molecular systematics would not view lobopods as linking arthropods and segmented worms. In light of the molecular data, that argument no longer seems credible.

In fact, the molecular data put nematode worms closer to arthropods -- but no one would have expected this on the basis of morphology because nematodes aren't segmented. Thus the molecular data implies segmentation is distributed in a paraphyletic fashion (i.e. a manner that doesn't fit with the nested hierarchy predicted by common ancestry) and lobopods aren't a good link between segmented worms and arthropods. Some lobopods do bear a certain resemblance to arthropods, but as one paper admits, "the origin of lobopods is still obscure."11 Another article states, "Lobopods in the Cambrian appear to be diverse and not particularly closely related to one another, and certainly cannot be combined in a monophyletic clade."12

Point 3: Not all phyla appear in the Cambrian.

The TO page asserts, "Only some phyla appear in the Cambrian explosion. In particular, all plants postdate the Cambrian, and flowering plants, by far the dominant form of land life today, only appeared about 140 Mya." This is an old argument -- but it's a red herring because no one argues that mammals or flowers appeared in the Cambrian explosion. What we see in the Cambrian event is the abrupt radiation of virtually all major animal body plans -- including vertebrate fish, without evolutionary precursors. This is a huge challenge to neo-Darwinian evolution, and this irrelevant point from the TO page doesn't help resolve it.

Point 4: The Cambrian explosion was not sudden.

Here, the TO page asserts, "Even the shortest estimate of five million years is hardly sudden." By admitting that the length of the Cambrian explosion might be only 5 or 10 million years, the TO page shows that, in quantitative terms, TalkOrigins does not dispute what ID proponents claim. But many sources plainly state that the Cambrian explosion was indeed quite "sudden" in geological terms. For example:

  • Robert Carroll wrote in the leading journal Trends in Ecology and Evolution that "within less then 10 million years, almost all of the advanced phyla appeared, including echinoderms, chordates, annelids, brachiopods, molluscs and a host of arthropods. The extreme speed of anatomical change and adaptive radiation during this brief time period requires explanations that go beyond those proposed for the evolution of species within the modern biota."13
  • Likewise, an article in the journal Development by three experts on the Cambrian event explains that, "The Cambrian explosion is named for the geologically sudden appearance of numerous metazoan body plans (many of living phyla) between about 530 and 520 million years ago, only 1.7% of the duration of the fossil record of animals."14
  • Or consider what a paper in Nature states: "Most major animal groups appear suddenly in the fossil record 550 million years ago."15
  • A paper in Science stated:
    Darwin recognized that the sudden appearance of animal fossils in the Cambrian posed a problem for his theory of natural selection. He suggested that fossils might eventually be found documenting a protracted unfolding of Precambrian metazoan evolution. Many paleontologiststo day interpret the absence of Precambrian animal fossils that can be assigned to extant clades not as a preservational artifact, but as evidence of a Cambrian or late Vendian origin and divergence of metazoan phyla. This would make the Cambrian the greatest evolutionary cornucopia in the history of the Earth. Definitive representatives of all readily fossilizable animal phyla (with the exception of bryozoans) have been found in Cambrian rocks, as have representatives of several soft-bodied phyla. Recent geochronological studies have reinforced the impression of a "big bang of animal evolution" by narrowing the temporal window of apparent divergences to just a few million years.16
  • Yet another paper in Science in 2011 states:
    When Charles Darwin published The Origin of Species (1), the sudden appearance of animal fossils in the rock record was one of the more troubling facts he was compelled to address. He wrote: "There is another and allied difficulty, which is much graver. I allude to the manner in which numbers of species of the same group, suddenly appear in the lowest known fossiliferous rocks" (p. 306). Darwin argued that the incompleteness of the fossil record gives the illusion of an explosive event, but with the eventual discovery of older and better-preserved rocks, the ancestors of these Cambrian taxa would be found. Studies of Ediacaran and Cambrian fossils continue to expand the morphologic variety of clades, but the appearance of the remains and traces of bilaterian animals in the Cambrian remains abrupt.17
  • Or as a paper in BioEssays states:
    [A]s explained on an intelligent-design t-shirt.
    Fact: Forty phyla of complex animals suddenly appear in the fossil record, no forerunners, no transitional forms leading to them; ''a major mystery,'' a ''challenge.'' The Theory of Evolution -- exploded again (idofcourse.com).
    Although we would dispute the numbers, and aside from the last line, there is not much here that we would disagree with. Indeed, many of Darwin's contemporaries shared these sentiments, and we assume -- if Victorian fashion dictated -- that they would have worn this same t-shirt with pride.18
Many similar citations could be given. But it seems that not only do scientific papers agree that the Cambrian explosion was less than 10 million years, but they also agree that it was geologically "sudden."

Point 5: There are plausible explanations for the Cambrian radiation.

This section of the TO page is sort of a free-for-all, listing a bunch of purportedly "plausible explanations for why diversification may have been relatively sudden." We've covered many of these here before on ENV.

The first one claims the Cambrian period simply represented the origin of hard parts: "These hard parts fossilize much more easily than the previous soft-bodied animals, leading to many more fossils but not necessarily more animals." As explained here, this argument is weak because the Cambrian fauna include many soft-bodied organisms; they too appeared explosively.

Another argument claims Precambrian animals were too small to be found: "Early complex animals may have been nearly microscopic." To bolster this claim, TO cites the supposed animal embryos found in the Doushantuo formation. But as we explain here, it's now thought that these weren't animal embryos at all. More importantly, even if those microscopic fossils were animals, it would only show, contrary to what TO claims, that the "microscopic" nature of an organism isn't a good explanation for why it wasn't fossilized. As Stephen Meyer and others explain here (writing about different sponge embryos):

If the fossil record has preserved such tiny organisms in Precambrian strata, why has it not preserved any of the allegedly miniature or soft-bodied ancestral forms of the animals that first appear in the Cambrian? If these strata can preserve embryos, then they should be able to preserve the ancestral animals to the new forms that arise in the Cambrian. But they do not.19
Other explanations listed on the TO page deal with changes in the oxygen content of the atmosphere or the ocean, a warming of the earth's temperatures, or other changes in the chemical makeup of the ocean. As we recently discussed here (Does Lots of Sediment in the Ocean Solve the "Mystery" of the Cambrian Explosion?), these types of explanations don't resolve the enigma of Cambrian explosion because they in no way explain the origin of the new information required to produce all of the new body plans that appeared in the Cambrian. As I wrote:
Citing increased chemical weathering around the time of the Cambrian explosion doesn't explain the abrupt appearance of new genes and other genetic information needed to generate new body plans. If they expect us to believe that sedimentation rates explain the sudden origin of new body plans, then it would seem that the Cambrian explosion is still a "mystery."
Substitute TO explanations like 'increased ocean oxygen levels' or 'fecal pellets' in the water' or 'warmer temperatures' for "increased chemical weathering" and you have the same problem.
Finally, one explanation for the Cambrian explosion on the TO page cites hox genes, stating "Hox genes, which control much of an animal's basic body plan, were likely first evolving around that time. Development of these genes might have just then allowed the raw materials for body plans to diversify (Carroll 1997)." There are serious problems with these types of "evo-devo" explanations as well.

First, developmental genes like Hox genes are tightly interconnected. Changes in one will affect many others, making most mutations lethal. As one writer cautioned in Nature, "macromutations of this sort are probably frequently maladaptive."20

Second, Hox genes do not really provide the "raw materials" for building body plans because they don't encode body parts. They merely direct the genes that encode body parts. At most, Hox mutations can only re-arrange parts that are already there; they cannot create truly novel structures:

[H]omeobox genes are selector genes. They can do nothing if the genes regulated by them are not there. ... It is totally wrong to imply that an eye could be produced by a macromutation when no eye was ever present in the lineage before.21

Third, despite years of research, the best examples of evolutionary change produced by evo-devo mechanisms remain extremely modest. They often entail loss, rather than gain of function.22 Some of the most impressive evidence for evo-devo amounts to mere changes in coloration spots on the wings of fruit flies.23 Obviously such small-scale changes will not produce new body plans.

One paper in BioEssays candidly admitted we still don't have a solution to the Cambrian mystery:

Thus, elucidating the materialistic basis of the Cambrian explosion has become more elusive, not less, the more we know about the event itself, and cannot be explained away by coupling extinction of intermediates with long stretches of geologic time, despite the contrary claims of some modern neo-Darwinists."24
Point 6: The Cambrian animals are unlike anything alive today.

The TO page states, "Cambrian life was still unlike almost everything alive today." It's not clear why that would help bolster an evolutionary explanation for the Cambrian explosion, but in any case, it's not really correct. Many, if not the vast majority of Cambrian fossils fit into modern animal phyla, and some are highly similar to living species -- including fish in the Cambrian explosion.

Point 7: There are other explosions.

Finally, the TO page states, "Major radiations of life forms have occurred at other times, too," but again, it's not clear how this fact helps at all to explain the Cambrian explosion. Indeed the observation that there have been other explosions at other periods across life's history just shows how hard it is for Darwinian evolution to explain much that's happened in that history. For example:

  • Most major fish groups appear abruptly.25

  • Plant biologists observe that the initial appearance of many land plants "is the terrestrial equivalent of the much-debated Cambrian 'explosion' of marine faunas."26

  • Later in the fossil record there is an explosion of flowering plants, sometimes referred to as the "big bloom."27

  • Vertebrate paleontologists believe there was a mammal explosion because of the abrupt appearance of many order of mammals. As Niles Eldredge, an evolutionary paleontologist and curator at the American Museum of Natural History, explains: "there are all sorts of gaps: absence of gradationally intermediate 'transitional' forms between species, but also between larger groups -- between, say, families of carnivores, or the orders of mammals."28

  • There is also a bird explosion, because major bird groups appear in a short time period.29

  • Some have even alluded to the abrupt origin of our own genus, Homo, as an explosion.30
These other explosions might be as much a problem for Darwinian evolution as the Cambrian explosion.

In responding to the TalkOrigins page, Jonathan M. concluded: "TalkOrigins has failed to provide us with a feasible naturalistic explanation for the Cambrian explosion. The facts that the article draws upon are either irrelevant to the subject at hand or accentuate the problem. The Cambrian explosion continues to represent a formidable challenge to the neo-Darwinian theory of evolutionary gradualism." After going through the same page, I draw the same conclusion.

References Cited:

[1.] James Valentine, On the Origin of Phyla (University of Chicago Press, 2004), p. 35.

[2.] Charles Marshall, "Explaining the Cambrian 'Explosion' of Animals," Annual Review of Earth and Planetary Sciences, 34 (2006):355-384.

[3.] Peter Douglas Ward, On Methuselah's Trail: Living Fossils and the Great Extinctions (W. H. Freeman, 1992), p. 36.

[4.] Alan Cooper and Richard Fortey, "Evolutionary explosions and the phylogenetic fuse," Trends in Ecology and Evolution, 13 (April, 1998): 151-156.

[5.] Andrew H. Knoll, and Sean B. Carroll, "Early animal Evolution: Emerging Views from Comparative Biology and Geology," Science, 284 (June 25, 1999): 2129-2136 (internal citations omitted).

[6.] Vicki Pearse, John Pearse, Mildred Buchsbaum, and Ralph Buchsbaum. Living Invertebrates (Blackwell Scientific Publications, 1987), , p. 764.

[7.] James W. Valentine, D. Jablonski, Doug H. Erwin, "Fossils, molecules and embryos: new perspectives on the Cambrian Explosion," Development, 126 (1999): 851-859 (internal citations omitted).

[8.] Richard Fortey, "Evolution: The Cambrian Explosion Exploded?," Science, 293 (July 20, 2001): 438-439 (emphases added).

[9.] Maximilian J. Telford, Sarah J. Bourlat, Andrew Economou, Daniel Papillon and Omar Rota-Stabelli, "The evolution of the Ecdysozoa," Philosphical Transactions of the Royal Society B, 363 (2008): 1529-1537.

[10.] This is another good example where the molecular data conflicts with morphological data. As Graham Budd explains, if arthropods are distantly related to annelids, "then the striking resemblance of such arthropod systems to (for example) those of annelids would be a convergence, which may be considered by some to be unlikely." See Graham E. Budd, "Tardigrades as 'Stem-Group Arthropods': The Evidence from the Cambrian Fauna," Zoologischer Anzeiger: A Journal of Comparative Zoology, 240 (2001): 265-279 (internal citations omitted). Or as another paper put it, the molecular data imply "the closest relatives of panarthropods are not segmented, coelomate animals like annelids, but rather are nonsegmented, mostly acoelomateworms with terminal mouth." Gregory D. Edgecombe, "Palaeontological and Molecular Evidence Linking Arthropods, Onychophorans, and other Ecdysozoa," Evo Edu Outreach (2009) 2:178-190. Since arthropods are segmented and coelomate animals, this finding is most surprising.

[11.] Jianni Liu, Degan Shu, Jian Han, Zhifei Zhang, Xingliang Zhang, "Origin, diversification, and relationships of Cambrian lobopods," Gondwana Research, 14 (2008): 277-283.

[12.] Graham E. Budd, "Tardigrades as 'Stem-Group Arthropods': The Evidence from the Cambrian Fauna," Zoologischer Anzeiger: A Journal of Comparative Zoology, 240 (2001): 265-279.

[13.] Robert L. Carroll, "Towards a new evolutionary synthesis," Trends in Ecology and Evolution, 15 (2000):27-32 (internal citations removed).

[14.] James W. Valentine, David Jablonski and Douglas H. Erwin, "Fossils, molecules and embryos: new perspectives on the Cambrian explosion," Development, 126 (1999): 851-859.

[15.] Philippe Janvier, "Catching the first fish," Nature, 402 (November 4, 1999): 21-22 (emphasis added).

[16.] Gregory A. Wray, Jeffrey S. Levinton, Leo H. Shapiro, "Molecular Evidence for Deep Precambrian Divergences Among Metazoan Phyla," Science, 274:568-573 (October 25, 1996) (internal citations removed) (emphases added.)

[17.] Douglas H. Erwin, Marc Laflamme, Sarah M. Tweedt, Erik A. Sperling, Davide Pisani, Kevin J. Peterson, "The Cambrian Conundrum: Early Divergence and Later Ecological Success in the Early History of Animals," Science, 334 (November 25, 2011): 1091-1097 (internal citations removed) (emphases added).

[18.] Kevin J. Peterson, Michael R. Dietrich and Mark A. McPeek, "MicroRNAs and metazoan macroevolution: insights into canalization, complexity, and the Cambrian explosion," BioEssays, 31 (1009): 736-747 (internal citations removed) (emphasis added).

[19.] Stephen C. Meyer, Marcus Ross, Paul Nelson, and Paul Chien, "The Cambrian Explosion: Biology's Big Bang," Darwinism, Design and Public Education (Michigan State University Press, 2003).

[20.] Eörs Szathmáry, "When the means do not justify the end, Book review of Sudden Origins: Fossils, Genes, and the Emergence of Species by Jeffrey H. Schwartz," Nature, 399 (June 24, 1999): 745-746.

[21.] Ibid.

[22.] See Hopi E. Hoekstra and Jerry A. Coyne, "The Locus of Evolution: Evo Devo and the Genetics of Adaptation," Evolution, 61-5 (2007): 995-1016.

[23.] See for example, Benjamin Prud'homme, Nicolas Gompel, and Sean B. Carroll, "Emerging principles of regulatory evolution," Proceedings of the National Academy of Sciences USA, 104 (May 15, 2007): 8605-8612.

[24.] Kevin J. Peterson, Michael R. Dietrich and Mark A. McPeek, "MicroRNAs and metazoan macroevolution: insights into canalization, complexity, and the Cambrian explosion," BioEssays, 31 (1009): 736-747 (internal citations removed).

[25.] Arthur N. Strahler, Science and Earth History: The Evolution/Creation Controversy (New York: Prometheus Books, 1987), 408-409.

[26.] Richard M. Bateman, Peter R. Crane, William A. DiMichele, Paul R. Kenrick, Nick P. Rowe, Thomas Speck, and William E. Stein, "Early Evolution of Land Plants: Phylogeny, Physiology, and Ecology of the Primary Terrestrial Radiation," Annual Review of Ecology and Systematics, 29 (1998): 263-292.

[27.] See Stefanie De Bodt, Steven Maere, and Yves Van de Peer, "Genome duplication and the origin of angiosperms," Trends in Ecology and Evolution, 20 (2005): 591-597. ("Angiosperms appear rather suddenly in the fossil record... with no obvious ancestors for a period of 80-90 million years before their appearance").

[28.] Niles Eldredge, The Monkey Business: A Scientist Looks at Creationism (New York: Washington Square Press, 1982), 65.

[29.] See Alan Cooper and Richard Fortey, "Evolutionary Explosions and the Phylogenetic Fuse," Trends in Ecology and Evolution, 13 (April, 1998): 151-156; Frank B. Gill, Ornithology, 3rd ed. (New York: W.H. Freeman, 2007), 42.

[30.] See "New study suggests big bang theory of human evolution," University of Michigan News Service (January 10, 2000).


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