Schizophrenia may have emerged after human–Neanderthal evolutionary split

The Neanderthals may have lacked the facile mind for language we modern humans enjoy, but they may also have been spared certain mind-altering disorders, such as schizophrenia. It appears that genetic changes that help define modern humans may also play a significant role in the development of the hallucinations and delusions that characterize schizophrenia. A recent genetic analysis that compared data from genome-wide association studies of people who have schizophrenia with Neanderthal genomic information revealed that risk loci were more likely to be found in regions that diverged from the Neanderthal genome. The study, published in the journal Biological Psychiatry, included an analysis of loci associated with evolutionary markers. The findings suggest that several of these gene variants related to cognitive processes have undergone selection. According to senior author Ole Andreassen from the University of California, San Diego, and the University of Oslo, Norway, schizophrenia may be a “side effect” of advantageous gene variants related to the acquisition of human traits such as language and complex cognitive skills. These variants may also have increased our propensity to developing psychoses. “Our findings suggest that schizophrenia vulnerability rose after the divergence of modern humans from Neanderthals,” said Andreassen in a supplementary report released by the journal, “and thus support the hypothesis that schizophrenia is a by-product of the complex evolution of the human brain.” —Karyn Hede, News Editor

The plague: it’s ba-ack

In the complex and intertwined history of human disease, few organisms inspire fear like the infectious bacterium Yersinia pestis. History serves notice that plague, now confined to a few reservoirs of endemic disease, could re-emerge without warning. Y. pestis has been causing documented pandemics throughout human history. The Justinian pandemic in the sixth to eighth centuries AD was the first such recorded, but the extent of disease and geographical reach are not well understood. Now, a genomic sequencing effort has produced a high-quality Y. pestis sequence that offers insight into its evolutionary history, its key mutational changes in virulence-associated genes, and possibly its potential for re-emergence. Investigators based in Munich, Germany, extracted genetic material from the tooth pulp of skeletons buried in the sixth century in an early medieval settlement, Altenerding, in southern Germany, near Aschheim, the source of an earlier sequenced plague genome from the same pandemic. The more recent sequence, published in the journal Molecular Biology and Evolution in September 2016, reached much higher coverage than the earlier sequencing effort, allowing investigators to correct 19 false-positive mutations reported in the published draft genome, as well as to identify 30 new mutations. Their findings point to a bacterial source with low genetic diversity in a rural region of southern Germany in the sixth century, as the two genomes extracted in the region were nearly identical. Future investigations may reveal the range of the outbreak and enable investigators to trace the path of the disease and its transmission rate. The investigators also suggest that comparing the genome structure of historical Y. pestis strains to those of extant strains and to that of the related soil- and water-borne organism Yersinia pseudotuberculosis could offer insights into key evolutionary changes, such as those in virulence-associated genes, through time. In addition, the results could inform preparation for a public health emergency, as plague is classified as a re-emerging infectious disease with reservoirs on nearly every major continent. ­—Karyn Hede, News Editor