The Biological Big Bang model for the major transitions in evolution

Abstract

Background: Major transitions in biological evolution show the same pattern of sudden emergence of diverse forms at a new level of complexity. The relationships between major groups within an emergent new class of biological entities are hard to decipher and do not seem to fit the tree pattern that, following Darwin's original proposal, remains the dominant description of biological evolution. The cases in point include the origin of complex RNA molecules and protein folds; major groups of viruses; archaea and bacteria, and the principal lineages within each of these prokaryotic domains; eukaryotic supergroups; and animal phyla. In each of these pivotal nexuses in life's history, the principal "types" seem to appear rapidly and fully equipped with the signature features of the respective new level of biological organization. No intermediate "grades" or intermediate forms between different types are detectable. Usually, this pattern is attributed to cladogenesis compressed in time, combined with the inevitable erosion of the phylogenetic signal.

Functional Class I and II Amino Acid-activating Enzymes Can Be Coded by Opposite Strands of the Same Gene

“…The corner between what in full-length crystal structures is the ␣-helix and the second ␤-strand of the Class I 46-mer occurs with minimal variation of amino acid, spacing, and three-dimensional packing in ϳ125 different protein families from the Rossmannoid superfamily (44), the largest in the proteome (47)(48)(49). P-loop peptides studied by also arguably have structural homology to parts of the Class I aaRS 46-mers that bind ATP; the segment N-terminal to the first helix shares glycines in homologous positions before, within, and following the Class I HIGH signature.…”

Proteome of Hydra Nematocyst

“…6). We assume that the vesicular environment was optimized for ECM assembly as a basis for an accelerated adaptation (41) under the pressure of a beginning predatory phase among eukaryotes that, in turn, has led to a variety of extrusive organelles exhibiting sophisticated discharge mechanisms (Fig. 6) (42).…”

Virus World as an Evolutionary Network of Viruses and Capsidless Selfish Elements

“…5). It is difficult to ascertain the relative contributions to this characteristic pattern of the loss of information over the course of evolution, resulting in the failure of the evolution models underlying phylogenetic methods, and actual explosive, Big Bang-like evolution (compressed cladogenesis) associated with such major radiations (23,(77)(78)(79)(80). Regardless, it is impossible to rely fully on the RT tree to reconstruct the evolution of retroelements.…”