I’ve just come across this excellent article in the current issue of PNAS – by science writer Megan Scudellari. The article is liberally sprinkled with quotes from the doyen of the so-called “old friends” hypothesis, Graham Rook of University College, London, and his colleague from the London School of Hygiene and Tropical Medicine, Sally Bloomfield. Both argue that the term “hygiene hypothesis” is an historical anachronism and a misnomer because it is widely taken to mean that the key to later immune health requires a slackening in standards of hygiene, and that an obsession with hygiene and antimicrobial cleaning products is to blame for the current epidemics of allergic and autoimmune diseases. Although none of this will come as much of a surprise to members of the evmed community this is a very readable and well researched piece which seeks to replace the literal interpretation of the hygiene hypothesis with the understanding that it is the dysbiosis of the gut microbiome that is to blame for the poor regulation of our immune systems. Rook is quoted and saying: “We know an awful lot now about why our immune system’s regulation is not in terribly good shape, and it’s got absolutely nothing to do with hygiene,” while Bloomfield weighs in with: “I’ve even seen things in the media saying we shouldn’t wash our hands. What the hell are they talking about?” Well worth a read.
The 1966 publication of Adaptation and Natural Selection by George Williams was a milestone for biology in general, and a seminal event for evolution and medicine. As Boomsma argues in this article from Current Biology celebrating the 50th anniversary of its publication, ” Adaptation by natural design: Williams’ paradigmatic synthesis is as valid as ever.” It is a superb summary of why group selection approaches are mostly irrelevant, making clear that “A major theme throughout Williams’ book is that group selection can, under very restricted conditions, produce changes in gene frequency in speciﬁc directions, but that it can never yield lasting group adaptations that cannot be better explained as individual adaptations of group members.”
Why do we still have an appendix? Measuring only 10 cm long and 7 mm wide, it must be one of the most troublesome vestigial organs in the human body. A quarter of a million cases of appendicitis were accounted for in the US in the five years between 1979 and 1984 and your life-time risk of appendicitis is 8.6% for males and 6.7% for females. A paper in The Lancet documents about 16 million cases of appendicitis world-wide in 2013, which resulted in 72,000 deaths globally. This is bound to be an underestimate. Even if appendicitis is only suspected you may well be in for preventative surgery. According to a paper in the American Journal of Epidemiology, an estimated 36 incidental procedures to remove the appendix are performed in the US to prevent one actual case of appendicitis. Acute appendicitis is horribly painful but a ruptured appendix can be fatal.
For a few years now, Rosa Krajmalnik-Brown from ASU has been researching whether the microbiota are implicated in autism spectrum disorder, either by affecting a range of measurable behavioural characteristics of ASD or by affecting the gastro-intestinal discomfort that often accompanies ASD and where the severity of GI complications mirrors the severity of ASD symptomatology. A paper published online today in the journal Microbiome reports on a small study, together with collaborators from Northern Arizona University, Ohio State University, and the University of Minnesota, on the effectiveness of regular microbiome transplants into children with autism spectrum disorder. And there are linked Eurekalert press releases from ASU and OSU. On an admittedly small sample group of 18 people aged 7 to 16 years old with ASD they demonstrated an average 80 percent improvement of gastrointestinal symptoms associated with autism spectrum disorders and 20-25 percent improvement in autism behaviors, including improved social skills and better sleep habits, among improvements in other measures of autism-related behaviour as tested on a recognised scale.
There is reason to believe that among the key traits that distinguish humans from the primates that are phylogenetically closest to us are cognitive and social abilities as exemplified by language and diverse aspects of social interaction and cultural expression. It is reasonable to speculate that these characteristic human phenotypes are based on differences from closely related species in neural development, which in turn ought to reflect differences in the nucleotide sequences of the genes that encode proteins or RNA molecules involved in this process. A study (1) published in Cell in October of this year by Christopher A. Walsh of Harvard Medical School, his associates, and collaborators from numerous institutions focuses on so-called human accelerated regions (HARs), portions of the human genome that have diverged more rapidly than other regions from the genomes of the species most closely related to humans. Doan et al. sought to identify mutations in HARs that are associated with abnormal cognition and social behavior of the sort that can be found in autism. (more…)