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Darwin’s Tree of Life was uprooted in the Cambrian explosion

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and didn’t get a chance to write anything down.

Darwin's Doubt Further to the fact that enough was known by 2009 to fell Darwin’s “tree of life,” which still flourishes in the vanished world of textbook certainties, here are some comments from Steve MeyerDarwin’s Doubt:

Vanderbilt University molecular systematist Antonis Rokas is a leader among biologists using molecular data to study animal phylogenetic relationships. Nevertheless, he concedes that a century and a half after The Origin of Species, “a complete and accurate tree of life remains an elusive goal.” In 2005, during the course of an authoritative study he eventually copublished in Science, Rokas was confronted with this stark reality. The study had sought to determine the evolutionary history of the animal phyla by analyzing fifty genes along seventeen taxa. He hoped that a single, dominant phylogenetic tree would emerge. Rokas and his team reported that “a 5-gene data matrix does not resolve relationships among most metazoan phyla” because it generated numerous conflicting phylogenies and historical signals. Their conclusion was candid: “Despite the amount of data and breadth of taxa analyzed, relationships among most metazoan phyla remained unresolved.”

In a paper published the following year, University of Wisconsin at Madison biologist Sean B. Carroll went so far as to assert that “certain critical parts of the TOL [Tree of Life] may be difficult to resolve, regardless of the quantity of conventional data available.” This problem applies specifically to the relationships of many of the animal phyla, where “[m]any recent studies have reported support for many alternative conflicting phylogenies.” Investigators studying the animal tree found that “ a large fraction of single genes produce phylogenies of poor quality” such that in one case, a study “omitted 35% of single genes from their data matrix, because those genes produced phylogenies at odds with conventional wisdom” Rokas and Carroll tried to explain the many contradictory trees by proposing that the animal phyla might have evolved too quickly for the genes to record some signal of phylogenetic relationships into the respective genomes. In their view, if the evolutionary process responsible for anatomical novelty works quickly enough, there would not be sufficient time for differences to accumulate in key molecular markers, in particular those used to infer evolutionary relationships in different animal phyla. Then, given enough time, whatever signal did exist might become lost. Thus, when groups of organisms branch rapidly and then evolve separately for long periods of time, this “can overwhelm the true historical signal”—leading to the inability to determine evolutionary relationships.

Their article brings the discussion of the Cambrian explosion full circle from an attempt to use genes to compensate for the absence of fossil evidence to the acknowledgment that genes do not convey any clear signal about the evolutionary relationships of the phyla first preserved by fossils in the Cambrian. (pp. 120–21)

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2 Replies to “Darwin’s Tree of Life was uprooted in the Cambrian explosion

  1. 1
    bornagain77 says:

    “Darwin’s Tree of Life was uprooted (and turned upside-down) in the Cambrian explosion”

    i.e. the fossil record is, in reality, opposite what we would expect if Darwinism were true:

    Disparity preceding Diversity graphic on Cambrian Explosion from ‘Darwin’s Doubt’
    http://www.evolutionnews.org/2.....74341.html

    “As Whittington analyzed the Cambrian fauna at the Burgess [in the 1960s], he realized that Walcott (before 1917) had grossly underestimated the morphological disparity of this group of animals. Many of the creatures in the assemblage featured unique body designs, unique anatomical structures, or both. Opabinia, with its five eyes, fifteen distinct segments, and claw at the end of a long proboscis exemplified the unique forms on display at the Burgess. But so did Hallucigenia, Wiwaxia, Nectocaris, and many other Burgess animals. To this day, paleontologists describing Nectocaris, for example, can’t decide whether it more closely resembles an arthropod, a chordate, or a cephalopod (a class of mollusk)”.
    Stephen Meyer – ‘Darwin’s Doubt’ (pp. 52–53).

    Challenging Fossil of a Little Fish
    “In Chen’s view, his evidence supports a history of life that runs opposite to the standard evolutionary tree diagrams, a progression he calls top-down evolution.”
    Jun-Yuan Chen is professor at the Nanjing Institute of Paleontology and Geology
    http://www.fredheeren.com/boston.htm

    Investigating Evolution: The Cambrian Explosion Part 1 – video
    http://www.youtube.com/watch?v=4DkbmuRhXRY
    Part 2 – video
    http://www.youtube.com/watch?v=iZFM48XIXnk

    The Ham-Nye Creation Debate: A Huge Missed Opportunity – Casey Luskin – February 4, 2014
    Excerpt: “The record of the first appearance of living phyla, classes, and orders can best be described in Wright’s (1) term as ‘from the top down’.”
    (James W. Valentine, “Late Precambrian bilaterians: Grades and clades,” Proceedings of the National Academy of Sciences USA, 91: 6751-6757 (July 1994).)
    http://www.evolutionnews.org/2.....81911.html

    In Explaining the Cambrian Explosion, Has the TalkOrigins Archive Resolved Darwin’s Dilemma? – JonathanM – May 2012
    Excerpt: it is the pattern of morphological disparity preceding diversity that is fundamentally at odds with the neo-Darwinian scenario of gradualism. All of the major differences (i.e. the higher taxonomic categories such as phyla) appear first in the fossil record and then the lesser taxonomic categories such as classes, orders, families, genera and species appear later. On the Darwinian view, one would expect to see all of the major differences in body plan appear only after numerous small-scale speciation events. But this is not what we observe.
    http://www.evolutionnews.org/2.....59171.html

    Jerry Coyne’s Chapter on the Fossil Record Fails to Show “Why Evolution is True” – Jonathan M. – December 4, 2012
    Excerpt: Taxonomists classify organisms into categories: species are the very lowest taxonomic category. Species are classified into different genera. Genera are classified into different families. Families are classified into different orders. Orders are classified into different classes. And classes are classified into different phyla. Phyla are among the very highest taxonomic categories (only kingdom and domain are higher), and correspond to the high level of morphological disparity that exists between different animal body plans. Phyla include such groupings as chordates, arthropods, mollusks, and echinoderms.
    Darwin’s theory would predict a cone of diversity whereby the major body-plan differences (morphological disparity) would only appear in the fossil record following numerous lower-level speciation events. What is interesting about the fossil record is that it shows the appearance of the higher taxonomic categories first (virtually all of the major skeletonized phyla appear in the Cambrian, with no obvious fossil transitional precursors, within a relatively small span of geological time). As Roger Lewin (1988) explains in Science,
    “Several possible patterns exist for the establishment of higher taxa, the two most obvious of which are the bottom-up and the top-down approaches. In the first, evolutionary novelties emerge, bit by bit. The Cambrian explosion appears to conform to the second pattern, the top-down effect.”
    Erwin et al. (1987), in their study of marine invertebrates, similarly conclude that,
    “The fossil record suggests that the major pulse of diversification of phyla occurs before that of classes, classes before that of orders, orders before that of families. The higher taxa do not seem to have diverged through an accumulation of lower taxa.”
    Indeed, the existence of numerous small and soft-bodied animals in the Precambrian strata undermines one of the most popular responses that these missing transitions can be accounted for by them being too small and too-soft bodied to be preserved.
    http://www.evolutionnews.org/2.....67021.html

    The unscientific hegemony of uniformitarianism – David Tyler – May 2011
    Excerpt: The pervasive pattern of natural history: disparity precedes diversity,,,, The summary of results for phyla is as follows. The pattern reinforces earlier research that concluded the Explosion is not an artefact of sampling. Much the same finding applies to the appearance of classes. These data are presented in Figures 1 and 2 in the paper.
    http://www.arn.org/blogs/index.....niformitar

    Disparity precedes diversity – graph
    http://www.veritas-ucsb.org/li.....ages/G.gif

  2. 2
    snelldl says:

    Apparently they can’t see the forest for the trees.

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