All known extant organisms are based on the same fundamental biochemical organisation: genetic information encoded as nucleic acid (DNA, or RNA for viruses), transcribed into RNA, then translated into proteins (that is, polymers of amino acids) by highly conserved ribosomes. The Genetic Code (the “translation table” between DNA and amino acids) is the same for almost every organism. This means that a piece of DNA in a bacterium codes for the same amino acid is the same as in a human cell.
11.4.1 DNA sequencing
Comparison of the DNA sequences allows organisms to be grouped by sequence similarity, and the resulting phylogenetic trees are typically congruent with traditional taxonomy. Sequence comparison is used to correct erroneous assumptions in the phylogenetic tree in instances where other evidence is scarce. Genetic sequence evidence thus allows inference and quantification of genetic relatedness between humans and other apes.
11.4.2 Other proteins
The proteomic evidence also supports the universal ancestry of life. Vital proteins, such as the ribosome, DNA polymerase, and RNA polymerase, are found in everything from the most primitive bacteria to the most complex mammals. The core part of the protein is conserved across all lineages of life, serving similar functions. Other similarities between all lineages of extant organisms, such as DNA, RNA, amino acids, and the lipid bi-layer, give support to the theory of common descent.
11.4.3 Evidence from antibiotic and pesticide resistance
The development and spread of antibiotic resistant bacteria, like the spread of pesticide resistant forms of plants and insects is evidence for evolution of species, and of change within species. Similarly, the appearance of DDT resistance in various forms of Anopheles mosquitoes, and the appearance of myxomatosis resistance in breeding rabbit populations in Australia, are all evidence of the existence of evolution.