Autism, the Evolution of Homo sapiens sapiens, and the Definition of “Human”

Autism, the Evolution of Homo sapiens sapiens, and the Definition of “Human”

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…)

A Method to Directly Visualize and Document Bacterial Evolution of Antibiotic Resistance as it Unfolds

A Method to Directly Visualize and Document Bacterial Evolution of Antibiotic Resistance as it Unfolds

The resistance of numerous bacterial pathogens of major clinical significance to many or all relevant antibiotics has become a public health threat of such magnitude that the latest U.N. General Assembly decided to hold a one-day meeting to address the issue (1). Recently, there has been substantial coverage of this issue in the general media, including by major news organizations such as the New York Times, National Public Radio, and the Washington Post (2-4). What the stories running in these outlets often fail to adequately emphasize is that the bacterial pathogens develop resistance to antibiotics by an evolutionary process. Furthermore, the solution to the problem of effectively treating these microbial agents of human disease requires not merely producing more antibiotics but also gaining deeper insights into the evolutionary processes by which antibiotic resistance comes into being and is transmitted between bacteria. In this context, a new study (5) from the laboratory of Roy Kishony, who is affiliated with both Technion and Harvard, is a novel and welcome advance in ways to study the evolution of bacterial antibiotic resistance and potentially to communicate about this process to the broader public. (more…)

Embracing a Fuller History of the Application of Evolution to Medicine

In a recent blog post (http://evmed.asu.edu/blog/evolutionary-medicine-top-ten-questions), Randy Nesse suggests that the presentations and discussions at the second annual conference of the International Society for Evolution, Medicine, and Public Health (ISEMPH) were

“… instigated 25 years ago as George Williams and I discussed and grappled with how evolution could be useful for medicine, and what to call the enterprise.”

In her chapter (Bentley, 2016) introducing the just published book, “Evolutionary Thinking in Medicine: from Research to Policy and Practice,” the author acknowledges activity that can be considered evolutionary medicine in the years prior to 1991 but confines it to before roughly 1940.  Following the end of World War II, Professor Bentley finds little to no evidence of significant work in the field until the 1990s.  Unfortunately, these claims disregard substantial numbers of evolution-related studies that either influenced fundamental understanding of human health and disease or affected medical practice. (more…)

Aminoacyl tRNA Synthetases: Exemplars of the Fluidity of Protein Structure and Function through Phylogenetic History

Earlier this year I was afforded the opportunity to hear Paul Schimmel, of the Scripps Research Institute, lecture on aminoacyl transfer RNA (tRNA) synthetases (aaRSs), a topic on which he is a leading authority.  These enzymes attach particular amino acids to specific tRNA molecules for incorporating those amino acids into growing polypeptide chains by ribosomes.  The basic features of these enzymes that contribute to the fundamental function of translating messenger RNAs (mRNAs) are conserved from humans through the most evolutionarily primitive single-celled organisms.  Thus these enzymes might be presumed to correspond to prototypical vegetative gene products, i.e., gene products necessary for essential cellular functions that have little to do with more recently evolved functions beyond protein synthesis.  So, it was extremely interesting to learn that in organisms that arose later in evolution there are other functions, unrelated to aminoacylation of tRNAs, associated with many of the aaRSs.  These functions of aaRSs are summarized by Guo and Schimmel (Nature Chem. Biol., 2013).

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Malaria-Specific Antibody Diversification via Interchromosomal Insertion of a Non-Immunoglobulin Gene Sequence

Identifying broadly neutralizing antibodies against infectious agents such as influenza A viruses, HIV, and Plasmodium falciparum that display impressive degrees of antigenic variation is a major focus of investigators developing therapeutics and vaccines for pathogens of importance in public health (Corti and Lanzavecchia, 2013).  In a previous post, I discussed one study (Klein et al., 2013) illustrating the sorts of unanticipated types of mutations found for broadly neutralizing antibodies against HIV.  Lanzavecchia and colleagues have now identified antibodies reactive with antigens encoded by different isolates of Plasmodium falciparum and expressed on infected erythrocytes (Nature, 2015).  They find an unexpected source for the heavy chain variable domain amino acid sequences that confer the broad anti-malarial reactivity against proteins in the RIFIN family. (more…)