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PLOS: Tree of life “problematic”

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new and expanded tree of life/Zosia Rostomian, Lawrence Berkeley

Open access paper, too, from PLOS:

A universal Tree of Life (TOL) has long been a goal of molecular phylogeneticists, but reticulation at the level of genes and possibly at the levels of cells and species renders any simple interpretation of such a TOL, especially as applied to prokaryotes, problematic.

So, even a tree of cellular lineages is not an unproblematic concept. Students of animals and plants have long accepted that incomplete lineage sorting, introgression, and full-species hybridization pose difficulties for the sorts of trees that Darwin might have had us draw. But it is microbes, with their promiscuous willingness to exchange genes between widely separated branches of any “tree,” that have most seriously jeopardized the neo-Darwinian synthesis, in the oversimplified form that we have often presented it to the public [45]. More sophisticated understandings do remain possible [3] and should be debated in a more conceptually and science-historically self-aware context [4]. – Doolittle WF, Brunet TDP (2016) What Is the Tree of Life? PLoS Genet 12(4): e1005912. doi:10.1371/journal.pgen.1005912 (public access) More.

Translation: It’s just not working anymore. Wasn’t that what Copernicus told the Pope when the Pope sent letters around asking for help reforming the Ptolemaic calendar?: The calendar doesn’t work because the theory is a mess. We heard that from Dava Sobel’s book, Galileo’s Daughter.

Can we strike a deal for “the leaf of life”? Yes, it raises all sorts of questions, but at least that thing looks like, well, …

See also:

The tree of life is mostly a complete mystery (so then how do we know it’s a tree?)

Kirk Durston on the new tree of life

Tree of life morphs into … leaf?

Maybe the Tree of Life is more of an art exhibit than a science pursuit?

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4 Replies to “PLOS: Tree of life “problematic”

  1. 1
    bornagain77 says:

    as to comment by Doolittle:

    More sophisticated understandings do remain possible

    Dr. Hunter observed “If major predictions of evolution are found to be false, that just means evolution is more complex than we thought.”

    “Being an evolutionist means there is no bad news. If new species appear abruptly in the fossil record, that just means evolution operates in spurts. If species then persist for eons with little modification, that just means evolution takes long breaks. If clever mechanisms are discovered in biology, that just means evolution is smarter than we imagined. If strikingly similar designs are found in distant species, that just means evolution repeats itself. If significant differences are found in allied species, that just means evolution sometimes introduces new designs rapidly. If no likely mechanism can be found for the large-scale change evolution requires, that just means evolution is mysterious. If adaptation responds to environmental signals, that just means evolution has more foresight than was thought. If major predictions of evolution are found to be false, that just means evolution is more complex than we thought.”
    ~ Cornelius Hunter

    and also commented

    “When their expectations turn out to be false, evolutionists respond by adding more epicycles to their theory that the species arose spontaneously from chance events. But that doesn’t mean the science has confirmed evolution as Velasco suggests. True, evolutionists have remained steadfast in their certainty, but that says more about evolutionists than about the empirical science.”
    ~ Cornelius Hunter

    Casey Luskin also once commented on the unfalsifiable nature of genetic trees:

    Shark Proteins Contradict the Standard Phylogeny of Vertebrates – Casey Luskin – January 6, 2014
    Excerpt: there’s almost no dataset that can contradict (falsify) common descent. Every time you find that one trait predicts one phylogeny, and another trait predicts a conflicting phylogeny, you can effect a reconciliation by invoking at will more evolutionary steps of convergent loss or gain of traits, or invoking a host of other ad hoc explanations. In a worst case scenario, if genes were distributed in the most un-treelike manner imaginable, I suppose you could take all the known genes present in the most recent presumed common ancestor of that group, and then simply invoke losses (and gains) of genes to reconcile the observed distribution with a tree. –

    Common Ancestry: Wikipedia vs. the Data – Casey Luskin – October 5, 2012
    Excerpt: In fact, the largest category of genes here is eukaryotic (cells with a nucleus) genes that have no homolog among prokaryotes (cells without a nucleus) — they don’t even have any possible candidate ancestors to explain where these genes came from, much less a consistent pattern of similarity pointing to one particular ancestor. All this is the opposite of “a direct correlation with common descent.”,,,
    ,,, if two phylogenetic trees aren’t congruent, the problem isn’t that common descent is wrong, but rather the conflict is simply evidence of HGT.,,, Syvanen, (in “Evolutionary Implications of Horizontal Gene Transfer,” Annual Review of Genetics, Vol. 46:339-356 (2012), invokes widespread HGT (Horizontal Gene Transfer), but he’s uncommonly honest about the data and its implications, offering the radical suggestion that “life might indeed have multiple origins.”,,,
    let’s now look within eukaryotes.,,,
    The biochemical organization of the innate immune systems of plants and animals is strikingly similar — but this is a direct non-correlation with common descent. Thus, evolutionary scientists are forced to call them “unexpectedly similar,” postulating that the similarities were “independently derived.” This data is not explained by Darwinian evolution and common descent. It is explained by common design.
    Somehow, something tells me not to expect any corrections over at Wikipedia.

    supplemental notes:

    “The genomic revolution did more than simply allow credible reconstruction of the gene sets of ancestral life forms. Much more dramatically, it effectively overturned the central metaphor of evolutionary biology (and, arguably, of all biology), the Tree of Life (TOL), by showing that evolutionary trajectories of individual genes are irreconcilably different. Whether the TOL can or should be salvaged—and, if so, in what form—remains a matter of intense debate that is one of the important themes of this book.”
    Koonin, Eugene V. (2011-06-23). The Logic of Chance: The Nature and Origin of Biological Evolution (FT Press Science) (Kindle Locations 76-80). Pearson Education (USA). Kindle Edition.
    more studies

    Reviewing The Evolution Revolution, the NCSE Offers Uninformed Criticism that Misses the Point – Lee M. Spetner – January 13, 2016
    Excerpt: Some researchers in the life sciences, who are not necessarily knowledgeable about evolution (including Levin), think that the various trees based on different biological systems or on protein- and DNA-sequence data yield the same tree. Life scientists once thought that trees based on anatomy and on the molecular sequences of proteins and DNA would be the same, but they were wrong (Nichols 2001; Degnan and Rosenberg 2006; Degnan and Rosenberg 2009; Heled and Drummond 2010; Rosenberg and Degnan 2010). They thought at least there would be consistency among the trees based on the DNA sequences of different genes, but again they were wrong. They then hoped that if they used the whole genome instead of individual genes, the data might average out and things would be better. In fact, it only made matters worse (Jeffroy et al. 2006; Dávalos et al. 2012). All this is discussed in my book. Levin is mistaken about what he calls the “cornerstone” of the evidence for common descent.
    He criticizes my rejection of common descent. I reject common descent because it is based on only circumstantial evidence. The drawback to circumstantial evidence is that it needs a valid theory to connect the evidence with the conclusion, and evolutionary theory is invalid, as I explain at length in my first chapter. There is thus no valid evidence for common descent — and certainly not what Levin calls its “cornerstone.”

    A New Model for Evolution: A Rhizome – Didier Raoult – May 2010
    Excerpt: Thus we cannot currently identify a single common ancestor for the gene repertoire of any organism.,,, Overall, it is now thought that there are no two genes that have a similar history along the phylogenic tree.,,,Therefore the representation of the evolutionary pathway as a tree leading to a single common ancestor on the basis of the analysis of one or more genes provides an incorrect representation of the stability and hierarchy of evolution. Finally, genome analyses have revealed that a very high proportion of genes are likely to be newly created,,, and that some genes are only found in one organism (named ORFans). These genes do not belong to any phylogenic tree and represent new genetic creations.

    Logged Out – Scientists Can’t Find Darwin’s “Tree of Life” Anywhere in Nature by Casey Luskin – Winter 2013
    Excerpt: the (fossil) record shows that major groups of animals appeared abruptly, without direct evolutionary precursors.
    Because biogeography and fossils have failed to bolster common descent, many evolutionary scientists have turned to molecules—the nucleotide and amino acid sequences of genes and proteins—to establish a phylogenetic tree of life showing the evolutionary relationships between all living organisms.,,,
    Many papers have noted the prevalence of contradictory molecule-based phylogenetic trees. For instance:
    • A 1998 paper in Genome Research observed that “different proteins generate different phylogenetic tree[s].”6
    • A 2009 paper in Trends in Ecology and Evolution acknowledged that “evolutionary trees from different genes often have conflicting branching patterns.”7
    • A 2013 paper in Trends in Genetics reported that “the more we learn about genomes the less tree-like we find their evolutionary history to be.”8
    Perhaps the most candid discussion of the problem came in a 2009 review article in New Scientist titled “Why Darwin Was Wrong about the Tree of Life.”9 The author quoted researcher Eric Bapteste explaining that “the holy grail was to build a tree of life,” but “today that project lies in tatters, torn to pieces by an onslaught of negative evidence.” According to the article, “many biologists now argue that the tree concept is obsolete and needs to be discarded.”,,,
    Syvanen succinctly summarized the problem: “We’ve just annihilated the tree of life. It’s not a tree any more, it’s a different topology entirely. What would Darwin have made of that?” ,,,
    “battles between molecules and morphology are being fought across the entire tree of life,” leaving readers with a stark assessment: “Evolutionary trees constructed by studying biological molecules often don’t resemble those drawn up from morphology.”10,,,
    A 2012 paper noted that “phylogenetic conflict is common, and [is] frequently the norm rather than the exception,” since “incongruence between phylogenies derived from morphological versus molecular analyses, and between trees based on different subsets of molecular sequences has become pervasive as datasets have expanded rapidly in both characters and species.”12,,,

  2. 2
    Mung says:

    So it’s not really a tree?

  3. 3
    daveS says:


    Can we strike a deal for “the leaf of life”? Yes, it raises all sorts of questions, but at least that thing looks like, well, …

    Can you give some examples of the sorts of questions that are raised?

    And more fundamentally, what’s the distinction between phylogenetic “leaves” and trees?

    Phylogenetic trees (including the Kumbaya circle) are described here.

  4. 4
    Zachriel says:

    Mung: So it’s not really a tree?

    There are many trees within the data. Metazoa and ribosomes form very distinct trees, for instance.

    The question is whether there is a single over-arching tree for all organisms. There are a number of mechanisms which confound the tree, including horizontal gene transfer and endosymbiosis. The base of the tree is especially obscure, and the common ancestor may be a disparate population rather than a single organism.

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