Evolutionary and Ecological Factors in Influenza A Virus Spread

In the May 26 (2011) issue of Nature, Vijaykrishna et al. address patterns of evolution and transmission exhibited by swine influenza A viruses (SwIV) isolated from pigs beings slaughtered in Hong Kong between May 1998 and January 2010.  Although the focus of the study is on viruses that circulate in swine, this study is relevant to human medicine and public health because these viruses can serve as the ancestors of viruses that infect people.  (more…)

Accessible Account of the Complexity of Complexity

Whatever definition is used, there is no shortage of complexity in biology, medicine, or of greatest relevance for this forum, evolutionary medicine.  As is made abundantly clear in the first-ever textbook of evolutionary medicine by Gluckman et al. (2010), in seeking to understand the evolutionary origins of human disease susceptibility there are profound challenges in charting genetic, developmental, and environmental influences on phenotype, and the interactions among these sources of variation can be exceptionally difficult to disentangle.  Therein resides one reasonable justification for reading Melanie Mitchell’s book, Complexity: A Guided Tour (2009). (more…)

Man, Machine, and Metaphorical Misdirection

The imitation of living and sentient beings by machines is recently much on the minds of many Americans.  A computer designed and built by scientists and engineers at IBM, “Watson,” convincingly defeated two former “Jeopardy” champions in a televised competition on the long-running game show.  This triumph of a machine over humans has stimulated both recollections of the last hallmark event in this series, the defeat (in six games in May of 1997) of chess grand master Garry Kasparov by another IBM computer, “Deep Blue,” and speculation about the future of artificial intelligence.  

Interest in the ability of computers to simulate human thought and intelligence persists in parallel with the tendency of many biologists and biomedical scientists to think of biochemical entities, (such as transcription, splicing, and signaling complexes), cells, and whole organisms as analogous to machines.  For example, the hijacking of cellular processes by viruses often invokes a phrase referring to the exploitation, by the virus, of cellular “machinery.”  Biologists frequently refer to cellular structures, like ribosomes, as “molecular machines.”  (more…)

The appendix, appendicitis, and appendectomy

The human appendix has long fascinated both biologists and physicians. A recent bout of appendicitis has heightened my interest in this organ and has stimulated me to write about it. Because of its small and variable size, anThe human vermiform appendix (image from the Talk Origins Archive; www.talkorigins.org)d its apparent uselessness, Darwin (1871) believed that the appendix was a rudiment, or vestigial organ. The caecum is large in many herbivores, in whom it is thought to play a role in the digestion of high-fiber foods. It presumably grew smaller during the course of primate evolution, leaving the appendix as a vestige. Like the rest of the colon, the appendix is rich in lymphatic tissue and its epithelial surface is coated with a biofilm. These properties have led to suggestions that the appendix has been preserved by natural selection because of its immunological functions or because it is a reservoir for commensal bacteria (Bollinger et al. 2007). It seems more likely, however, that these properties simply reflect the development of the appendix as part of the colon; there is little reason to believe that the appendix has unique or especially important immunological or microbiological functions. People who have their appendices removed or who are born with congenital absence of the appendix don’t exhibit any physiological deficits. Darwin was almost certainly correct—the appendix is a rudiment. (more…)