Common Descent

One of the main tenets of modern biology is the theory of universal common ancestry, or the idea that all living organisms can trace their genealogy back to mutual descendants. A recent paper has sought to further test that theory. It looked at the main domains of life (Eukarya, Bacteria and Archaea) and asked if their relationships are better defined by a unified common genetic relationship or by multiple lineages. The results were unequivocally in favour of UCA, but the introduction to the paper highlighted other, more general reasons for accepting the theory.

The evidence it listed was:
1) the agreement between phylogeny and biogeography
2) the correspondence between phylogeny and the palaeontological record
3) the existence of numerous predicted transitional fossils
4) the hierarchical classification of morphological characteristics
5) the marked similarities of biological structures with different functions
6) the congruence of morphological and molecular phylogenies
7) key commonalities at the molecular level
8) near universality of the genetic code