See Wikipedia:Evolution for basic understanding which is assumed in this Wiki for a theory first announced formally in 1858 based on the research of Alfred Russel Wallace and Charles Darwin. This understanding simplifies the interpretation of the contents of this wiki and application of that knowledge.
A critical modern concept is that the genetic material of individual species does not just evolve through horizontal transmission through the species but also there has been critically evolutionarily interchange between species. Thus the genome of the bacterium Wolbachia is found almost intact in some filarial nematodes and humans incorporate genes from viruses associated with human disease. This concept results in what has been termed the Darwinian rhizome as a better model for evolutionary relationships than the faulty Darwinian tree of the text books.
The recurrent laryngeal nerve in the human is one good illustration (even more so in the Giraffe) as is the course of the spinal accessory nerve that evolution proceeds by variation and selection rather than by design, whether intelligent, stupid, or flying and pastaform. One recent survey in Britain found that 52% did not think evolution best described their view of the origin and development of life. The authors would encourage any of those reading this site who wish to comprehend its contents to ensure they understand the concepts of evolution, even if they don't believe the theory, as it is impossible to explain many aspects of infectious disease or the body's response to disease in terms that have meaning with present alternative theories. An example is the use of the word evolve in the next paragraph !
Bacteria and particularly RNA viruses evolve in something very like real time. Accordingly a human generation time has seen the evolution of Staphylococcus aureus from an organism sensitive to substituted penicillins to one known to most as MRSA. The concepts involved in such evolution are self consistent and verifiable within the knowledge base attainable and needed by competent doctors to practice today to standards acceptable to the public. Accordingly doctors can find it extremely difficult to deal with those who reject the theory of evolution and promote inconsistent belief systems based on initial assumptions not open to challenge.
Recent Branches in Our Clade
See above for various references