RE: I 'believe' in Evolution
October 23, 2012 at 7:24 pm
(This post was last modified: October 23, 2012 at 7:27 pm by Whateverist.)
(October 23, 2012 at 8:50 am)Rhythm Wrote: Sigh sigh sigh, they're the same thing. The terms macro/micro evolution came about awhile back and have since utterly fallen out of favor, a distinction not worth making. The only people who insist on making this distinction are creatards who, for some reason, even though they love the fucking terms, can't get them right. The author of that article, for example, was making the claim that "microevolution" -by the definition he decided to give it at the start of the article- does not account for new organs. That many organs are retasked versions of older organs (that may no longer serve the same purpose) is fairly well understood, but lying that aside, new organs are not required for "macroevolution". We have hearts and so do rats. Again, the tears began at the beginning of the article when the author attempted to weasel in "the creation of new information/genes" as the criteria.
I think I'm agreeing with you, Rythym. No organism evolves an entirely new organ in one generation. It is a gradual repurposing. A really huge change is a journey of many generations, none of them teleological. microevolution is just small changes. Macroevolution is just many microevolutions stacked up over time. Or else there is just no need to make the distinction at all.
The other perspective needed to truly understand evolution is how an embryo assembles itself to develop into the organism it will be, sometimes refered to as "evo devo". I've been struggling to get my head around this but it does -potentially- greatly influence how we understand the process of evolution. At the risk of including too large of a quote here is one from wikipedia entry for "evo devo" which gives more detail. I've bolded the parts I think suggest impacts for our understanding of evolution.
Quote:Evolutionary developmental biology is not yet a unified discipline, but can be distinguished from earlier approaches to evolutionary theory by its focus on a few crucial ideas. One of these is modularity: as has been long recognized, plants and animal bodies are modular: they are organized into developmentally and anatomically distinct parts. Often these parts are repeated, such as fingers, ribs, and body segments. Evo-devo seeks the genetic and evolutionary basis for the division of the embryo into distinct modules, and for the partly independent development of such modules.
Another central idea is that some gene products function as switches whereas others act as diffusible signals. Genes specify proteins, some of which act as structural components of cells and others as enzymes that regulate various biochemical pathways within an organism. Most biologists working within the modern synthesis assumed that an organism is a straightforward reflection of its component genes. The modification of existing, or evolution of new, biochemical pathways (and, ultimately, the evolution of new species of organisms) depended on specific genetic mutations. In 1961, however, Jacques Monod, Jean-Pierre Changeux and François Jacob discovered within the bacterium Escherichia coli a gene that functioned only when "switched on" by an environmental stimulus.[7] Later, scientists discovered specific genes in animals, including a subgroup of the genes which contain the homeobox DNA motif, called Hox genes, that act as switches for other genes, and could be induced by other gene products, morphogens, that act analogously to the external stimuli in bacteria. These discoveries drew biologists' attention to the fact that genes can be selectively turned on and off, rather than being always active, and that highly disparate organisms (for example, fruit flies and human beings) may use the same genes for embryogenesis (e.g., the genes of the "developmental-genetic toolkit", see below), just regulating them differently.
Similarly, organismal form can be influenced by mutations in promoter regions of genes, those DNA sequences at which the products of some genes bind to and control the activity of the same or other genes, not only protein-specifying sequences. This finding suggested that the crucial distinction between different species (even different orders or phyla) may be due less to differences in their content of gene products than to differences in spatial and temporal expression of conserved genes. The implication that large evolutionary changes in body morphology are associated with changes in gene regulation, rather than the evolution of new genes, suggested that Hox and other "switch" genes may play a major role in evolution, something that contradicts the neo-darwinian synthesis.
Another focus of evo-devo is developmental plasticity, the basis of the recognition that organismal phenotypes are not uniquely determined by their genotypes. If generation of phenotypes is conditional, and dependent on external or environmental inputs, evolution can proceed by a "phenotype-first" route,[3][8] with genetic change following, rather than initiating, the formation of morphological and other phenotypic novelties.[clarification needed] The case for this was argued for by Mary Jane West-Eberhard in her 2003 book Developmental plasticity and evolution.[8]
