One does not have to go very deep into the evidences for variation in living things to find that gradualism does not fit the data. It should not be a controversial matter to say that Darwin's portrayal of a branching "Tree of Life" (TOL) is erroneous. However, allegiance to this metaphor has been fundamental for generations of Darwinists. Koonin writes: "Nevertheless, it is generally assumed that, in principle, the TOL exists and is resolvable although, in practice, full resolution might never be attained and, furthermore, might not even be particularly important for understanding the actual events that transpired during the respective transitional stages." Living with the theoretical model, in tension with the empirical data, has had a negative influence on evolutionary biologists, who appear to prefer fitting data into their theoretical models rather than testing their models against the evidence.
Koonin has made a radical and controversial contribution to the debate.
I argue for a fundamentally different solution, i.e., that a single, uninterrupted TOL does not exist, although the evolution of large divisions of life for extended time intervals can be adequately described by trees. I suggest that evolutionary transitions follow a general principle that is distinct from the regular cladogenesis. I denote this principle the Biological Big Bang ( BBB ) Model. Under this model, each of the biological transitions is, indeed, a transition in a more specific, technical sense, i.e., a switch between two phases of evolution, a phase of rapid evolution (inflation) characterized by rampant exchange and recombination of genetic material, followed by congealing into a relatively slow phase governed by the tree pattern.
This BBB model draws inspiration from cosmology. In particular, Koonin is impressed by inflation as the vehicle by which complexity (in the form of stars and galaxies) was generated.
However, the nature of the Big Bang event had not received a coherent explanation before the advent, in 1981, of a new generation of cosmological models that stem from the concept of inflation. Inflation is the exponentially fast initial expansion of a universe. Inflation is in an excellent agreement with several crucial results of observational cosmology. In the most plausible, self-consistent inflationary models, inflation is eternal, with an infinite number of island (pocket, bubble) universes (hereinafter, simply, universes) emerging through the decay of small regions of the primordial "sea" of false vacuum and comprising the infinite multiverse.
In the BBB model, there were biological analogues to inflation, whereby complexity emerged from precursors. This involves extensive genetic exchanges and structural reorganisations that are essentially unpredictable and therefore have the corollary that "there is no TOL". Indeed, "the BBB model defies the TOL paradigm". Darwinism can have a place in understanding the "slow phase" of biological variation, but not those that are abrupt: "understanding the inflationary phases and the exact processes occurring during BBBs emerges as a major goal of evolutionary biology."
One reviewer of this paper noted the words: "In each major class of biological objects, the principal types emerge "ready-made", and intermediate grades cannot be identified" and commented: "Ouch, that will be up on ID websites faster than one can bat an eye." All credit to Koonin for his response:
Here I do not really understand the concern. I changed "ready-made" to "abruptly", to avoid any ID allusions and added clarifications but, beyond that, there is little I can do because this is an important sentence that accurately and clearly portrays a crucial and, to the very best of my understanding, real feature of evolutionary transitions. Will this be used by the ID camp? Perhaps - if they read that far into the paper. However, I am afraid that, if our goal as evolutionary biologists is to avoid providing any grist for the ID mill, we should simply claim that Darwin, "in principle", solved all the problems of the origin of biological complexity in his eye story, and only minor details remain to be filled in.
There's some good advice here! Let's hope the debaters take this challenge seriously.
The Biological Big Bang model for the major transitions in evolution
Eugene V Koonin
Biology Direct 2007, 2:21doi:10.1186/1745-6150-2-21 [open access]
From the Abstract:
Hypothesis: I propose that most or all major evolutionary transitions that show the "explosive" pattern of emergence of new types of biological entities correspond to a boundary between two qualitatively distinct evolutionary phases. The first, inflationary phase is characterized by extremely rapid evolution driven by various processes of genetic information exchange, such as horizontal gene transfer, recombination, fusion, fission, and spread of mobile elements. These processes give rise to a vast diversity of forms from which the main classes of entities at the new level of complexity emerge independently, through a sampling process. In the second phase, evolution dramatically slows down, the respective process of genetic information exchange tapers off, and multiple lineages of the new type of entities emerge, each of them evolving in a tree-like fashion from that point on. [snip]
Conclusion: A Biological Big Bang ( BBB ) model is proposed for the major transitions in life's evolution. According to this model, each transition is a BBB such that new classes of biological entities emerge at the end of a rapid phase of evolution (inflation) that is characterized by extensive exchange of genetic information which takes distinct forms for different BBBs. The major types of new forms emerge independently, via a sampling process, from the pool of recombining entities of the preceding generation. This process is envisaged as being qualitatively different from tree-pattern cladogenesis.
Quote from the Background: "There seems to be a striking commonality between all major transitions in the evolution of life. In each new class of biological objects, the principal types emerge abruptly, and intermediate grades (e.g., intermediates between the precellular stage of evolution and prokaryotic cells or between prokaryotic and eukaryotic cells), typically, cannot be identified."
Crowther, R., Darwin Doubting Heretic Reveals Himself at National Center for Biotechnology, Evolution News & Views, 9 October 2007.
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