The common understanding is that the evolution, as a whole, of all species on the planet throughout history has been the result of a general trend of increasing complexity. By the standard ToE, directionality in the history of life is commonly framed in terms of six major evolutionary steps, or megatrajectories
(1) evolution from the origin of life to the last common ancestor of extant organisms,
(2) the metabolic diversification of bacteria and archaea,
(3) evolution of eukaryotic cells,
(5) the invasion of the land and
(6) technological intelligence.
evolutionary theory has traditionally held that very long periods of time are needed for natural selection to generate extreme differences in morphological organization like those seen in animal body plans. Each major transitional step would require increase of genome complexity, and the arise of new genomic specified complex information through mutations and natural selection would result directly in the increase of complexity of body plans and new species.
The scientific evidence however points to a different picture. Several lines of evidence refute this darwinian prediction :
Kurland CG et al write in their remarkable paper : " Genomics and the irreducible nature of eukaryote cells " following:
Comparative genomics shows that, under certain ecological settings, sequence loss and cellular simplification are common modes of evolution. Comparative genomics has confirmed a lesson from paleontology: Evolution does not proceed monotonically from the simpler to the more complex . Comparative genomics, aided by proteomics of cellular signature structures (CSSs) such as the mitochondria , nucleoli, and spliceosomes, reveals hundreds of proteins with no orthologs (ortholog = two or more homologous gene sequences found in different species related by linear descent ) evident in the genomes of prokaryotes.
That is one of the reasons, why i doubt common ancestry is true. There is no reason to believe eukaryotes evolved from prokaryotes and archaea
Examples of ecological circumstances driving genome reduction are seen in many intracellular endosymbionts and parasites, which gain few genes but lose many genes responsible formetabolic flexibility The mitochondrion is even more extreme in its reductive evolution; its ancestral bacterial genome has been reduced to a vestigial microgenome supported by a predominantly eukaryote proteome. Genomes of modern mitochondria encode between 3 and 67 proteins, whereas the smallest known free-living a-proteobacterium (Bartonella quintana) encodes 1100 proteins. Taking Bartonella as a minimal genome for the freeliving ancestor of mitochondria, nearly all of the bacterial coding sequences have been lost from the organelle, though not necessarily from the eukaryote cell. The mitochondrial genome of the protist Reclinomonas americana is the largest known but has still lost more than 95% of its original coding capacity. This abbreviated account of genome reduction illustrates the Darwinian view of evolution as a reversible process in the sense that ‘‘eyes can be acquired and eyes can be lost.’’ Genome evolution is a two-way street. This bidirectional sense of reversibility is important as an alternative to the view of evolution as a rigidly monotonic progression from simple to more complex states, a view with roots in the 18th-century theory of orthogenesis. Unfortunately, such a model has been tacitly favored by molecular biologists who appeared to view evolution as an irreversible march from simple prokaryotes to complex eukaryotes, from unicellular to multicellular. The many well documented instances of genome reduction provide a necessary corrective measure to the often-unstated assumption that eukaryotes must have originated from prokaryotes.
Last edited by Admin on Fri Dec 23, 2016 8:01 am; edited 1 time in total