by Leonie P.

Evidence of evolution

Hierarchical organization of life. Assuming a historical process of branching and diverging best reflects biological reality of species and higher-order groups with ever decreasing similarity. It is superior to any other organizing system proposed so far.

• Homology. Similarity of structure despite differences in function is best explained by shared ancestry, not by best design.

• Embryological similarities. Homologous characters not needed at later life stages appear transitorily during embryological development. This can only be understood by shared ancestry.

• Vestigial characters. There are numerous examples of ancestral features that are degenerated and of no use to the remnant organism. Cave dwelling fish e.g. display eyes in every stage of degeneration.

• Convergence. Functionally similar features often evolved independently and differ profoundly in structure. This provides evidence for adaptation by natural selection and cannot be understood by the hypotheses of optimal design.

• Suboptimal design. Indeed, many structures show suboptimal design (e.g. blind spot in human eye) and can only be understood by historical constraint. Evolution simply has to work with the variation present at the time.

• Geographic distributions. The distributions of many taxa align well with what we know from the movement of plate tectonics and don’t make sense without assuming contiguous change from a common ancestor.

• Intermediate forms. The hypothesis of evolution proceeding by gradual small change is well supported by intermediate forms, both in living organisms (some snakes still have vestigial legs) and fossils (e.g. Archaeopterix).

• Fossils. Though incomplete, the fossil record in conjunction with radioactive dating clearly demonstrates that evolution is a long, historical process of change. Dinosaurs are simply not found in the same strata as humans.

• Molecular evidence. Common ancestry is seen in a large variety of molecular properties (codon usage, basic molecular machinery, organelles, etc.) and homologies displaying similar functionality across millions of years (if you insert a mouse ‘eye’ gene into drosophila it will start making an eye providing evidence for a shared bilaterian ancestor).


Leonie P.


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