Here is another post as the field seems to progress so fast with a new study on enterotypes of the human gut microbiome from
22 newly sequenced faecal metagenomes of individuals from four countries with previously published data sets, here we identify three robust clusters (referred to as enterotypes hereafter) that are not nation or continent specific.
The 3 clusters are Bacteroides (enterotype 1), Prevotella (enterotype 2) and Ruminococcus (enterotype 3) – no idea if these are under selective pressure from the host (genes!), from enviroment (antibiotics!) or from microbial competitors. When we look, however, at another study published also last week at Science magazine, it seems that at least one cluster has it’s own trick to get the right of residence by synthesizing a symbiosis factor. Continue reading Will the bacterial flora protect you from you allergies?
I need to refer here to a post 3 years ago and the medical literature that genes frequencies may have changed rapidly between generations.
Any empirical proof of this hypothesis, however, is scarce so far. Or I have to say, until this week, when I found a study published earlier in PLoS ONE that tackles this problem: Selection for Genetic Variation Inducing Pro-Inflammatory Responses under Adverse Environmental Conditions in a Ghanaian Population Continue reading Genes on the fast lane
(at least for scientists) is the possibility to annotate PDFs. Sorry, the screenshot originates from one the most stupid papers that I read over the past years but it nicely shows Continue reading The most significant improvement in Snow Leopard
A new paper in PLoS ONE argues that human languages may adapt like biological organisms. By doing a large-scale analysis of over 2,000 of the worldâ€™s languages the authors find striking relationships between the demographic properties of a languageâ€”such as its population and global spreadâ€”and the grammatical complexity of those languages. Languages with the most speakers (like English) were found to have far simpler grammars than languages spoken by few people and in circumscribed regions. This reminds me to bottlenecks in population history (and founder effects for certain DNA variants) while the authors describe this phenomenon as â€œLinguistic Nicheâ€. A Hardy Weinberg Equilibrium of declension types?
Funny to see this title at PNAS “Numbering the hairs on our head”
Evolution and medicine share a dependence on the genotypeâ€“phenotype map. Although genotypes exist and are inherited in a discrete space convenient for many sorts of analyses, the causation of key phenomena such as natural selection and disease takes place in a continuous phenotype space whose relationship to the genotype space is only dimly grasped.
The author was aware of the association to Continue reading Numbering the hairs on our head
A book review of “Why we get sick” at tennov.com writes
Bacteria can evolve as much in a day as we can in 1000 years and there are as many bacterial cells in each of our guts as there are people on earth. That even improbable mutations occur with frequency in populations of pathogens gives them a decided advantage […] As Nesse and Williams emphasize, the end of the war is nowhere in sight. The 20th century was the golden age of relief from infection, but it may be over and this may accurately be considered a “post-antimicrobiol era.”
The same fact in Mel Greaves’ writing (p 216)
Natural selection will have operated against individuals who inherited fatal conditions that strike early in life, and for those whose immune systems were bext equipped to restrain the ravages of plagues. The geneticist and polymath, J B S Haldane, was surely correct in suggesting that infections have been the most powerful ‘natural’ selective pressure acting on human populations.
Unaware of the Haldane quote Continue reading Why do we get asthma
According to Gluckman et al. 2009 (page 22) the beginnings of evolutionary ideas appeared at the end of the 18th century with natural science on the rise driven by Carl Linnnaeus and Georges-Louis Leclerc – the great cataloguers of a living species – and Erasmus Darwin and Jean-Baptiste Lamarck – the new interpreters of the tree of life. Of course there are more influential French scientists (Georges Cuvier, Etienne Geoffrey Saint-Hilaire) that had an impact on Darwin and Wallace and also Robert Chambers who argued for evolution under divine guidance. The main contribution, however, is the Origin of Species by Charles Darwin, the mutability of the genome, the importance of genetic variation and the importance of selection mechanisms. There was quite some silence after that lightning strike . Although mutation events were not questioned, William Bateson (as well as Thomas Morgan) believed more in saltatations, eg. undirected mutations. Only the great mathematicians Ronald Fisher, JBS Haldane and Sewall Wright ussed population genetics to unite modern genetics and evolutionary thoughts. While the mid 20thies biologists like Dobzhansky and Ernst Mayr enforced a naturalist’s perspective, a direct relationship to clinical medicine is being established only now with Continue reading Evolutionary Medicine – A brief history
At least in medicine but also in many other fields, formal proof of a scientific hypothesis is difficult if not impossible. Reading again Greaves’ cancer book, I discover even more insights there. Talking about the hormonal stress leading to breast cancer he makes the point that
there is no ’cause’ in the straightforward, singular, or usually perceived meaning of the word; no tubercle bacillus equivalent. Neither is a mutant gene the common cause. Chronic hormonal stimulation driving persistent epithelial stem cell division seems to be a major factor (cycles driving cycles) and this reflects in large measure our social divorce from evolutionary adaptations for reproduction … Superimpose some degree of inherited predisposition and chance itself on this prescription and a very plausible causal network imbued with evolutionary principles becomes evident.
This is a very different view to the current sequencing headlines like “Lung cancer and melanoma laid bare“.