Well… A Teoria da Evolução Tem Mudado muito, não é mais a Darwiniana que aprendemos na Escola

PZMayers no Pharyhgula faz uma longa atualizaçao do mais moderno status da evolução no entendimento dos biológos evolucionistas, hoje. E informa que depois de darwin a theoria mudou para varios outros nomes e conceitos.


Uma frase importante no texto é: ” And that, of course, demolishes the bogus distinction between historical and observational science that Ken Ham laughably makes. When I observe a fruit fly or a zebrafish or a human being, I am seeing its history made manifest in its structure.”

A seguir, apenas duas figuras expostas no texto de Mayers:

The state of modern evolutionary theory may not be what you think it is


Selectionist, neutral and nearly neutral theories. a | Selectionist theory: early neo-Darwinian theories assumed that all mutations would affect fitness and, therefore, would be advantageous or deleterious, but not neutral. b | Neutral theory: the neutral theory considered that, for most proteins, neutral mutations exceeded those that were advantageous, but that differences in the relative proportions of neutral sites would influence the rate of molecular evolution (that is, more neutral sites would produce a faster overall rate of change). c | Nearly neutral theory: the fate of mutations with only slight positive or negative effect on fitness will depend on how population size affects the outcome.

Postmodern reassessment of some central propositions of Darwin and Modern Synthesis
Proposition Postmodern status
The material for evolution is provided primarily by random, heritable variation. Only partly true. The repertoire of relevant random changes greatly expanded to include duplication of genes, genome regions, and entire genomes; loss of genes and generally, genetic material; HGT [horizontal gene transfer], including massive gene flux in cases of endosymbiosis; invasion of mobile selfish elements and recruitment of sequences from them; and more. More importantly, (quasi) directed (Lamarckian*) variation is recognized as a major factor of evolution.
Fixation of (rare) beneficial changes by natural selection is the main driving force of evolution. Only partly true. Natural (positive) selection is important but is only one of several fundamental factors of evolution and is not quantitatively dominant. Neutral processes combined with purifying selection dominate evolution, and direct effects of environmental cues on the genome ([quasi] Lamarckian phenomena) are important as well.
The variations fixed by natural selection are “infinitesimally small.” Evolution adheres to gradualism. False. Even single gene duplications and HGT of single genes are by no means “infinitesimally small,” nor are deletion or acquisition of larger regions, genome rearrangements, whole-genome duplications, and, most dramatically, endosymbiosis. Gradualism is not the principal regime of evolution. [And I would add that even point mutations can have large phenotypic effects. –pzm]
Uniformitarianism: Evolutionary processes have remained largely the same throughout the evolution of life. Only partly true. Present-day evolutionary processes were important since the origin of replication. However, major transitions in evolution, such as the origin of eukaryotes, could be brought about by (effectively) unique events such as endosymbiosis, and the earliest stages of evolution (pre-LUCA [last universal common ancestor]) partially relied on distinct processes not involved in subsequent “normal” evolution.
Evolution by natural selection tends to produce increasingly complex adaptive features of organisms, hence progress is a general trend in evolution. False. Genome complexity probably evolved as a “genomic syndrome” cause by weak purifying selection in small populations, not as an adaptation. There is no consistent trend toward increasing complexity in evolution, and the notion of evolutionary progress is unwarranted.
The entire evolution of life can be depicted as a single “big tree.” False. The discovery of the fundamental contribution of HGT and mobile genetic elements to genome evolution invalidates the TOL concept in its original sense. However, trees remain essential templates to represent evolution of individual genes and many phases of evolution in groups of relatively close organisms. The possibility of salvaging the TOL as a central trend of evolution remains.
All extant cellular life forms descend from very few ancestral forms (and probably one, LUCA). True. Comparative genomics leaves no doubt of the common ancestry of cellular life. However, it also yields indications that LUCA(s) might have been very different from modern cells.

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