Roebroeks, W. | bioRxiv Science

bioRxiv2018

Evolution of hominin detoxification: Neanderthal and modern human AHR respond similarly to TCDD

In studies of hominin adaptations to fire use, the role of the aromatic hydrocarbon receptor (AHR) in the evolution of hominin detoxification, especially regarding toxic smoke components, has been highlighted, including statements that the modern human AHR is significantly better at dealing with smoke toxins. We compared the AHR-controlled induction of cytochrome P450 1A1 (CYP1A1) in cultured cells transfected with an Altai-Neanderthal respectively a modern human reference AHR expression construct, and exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We compared the complete AHR mRNA sequences including the untranslated regions (UTRs), maintaining the original codon usage, in HeLa human cervix epithelial adenocarcinoma cells. Our experiments complement a previous study of the AHR coding region optimized for mammalian codon usage and expressed in rat cells. Our results show no significant difference in CYP1A1 induction by TCDD between Neanderthal and modern human AHR (instead of a previously reported 150-1000 times difference range before), demonstrating that expression in a homologous cellular background is of major importance. The two dose-response curves almost coincide, except for a higher extrapolated maximum induction level for the Neanderthal AHR, possibly caused by a 5-UTR G-variant known from modern humans (rs7796976). Our results are strongly at odds with a major role of the modern human AHR in the evolution of hominin detoxification of smoke components and consistent with our previous study which concluded that efficient detoxification alleles are more dominant in ancient hominins than in modern humans based on 18 relevant genes in addition to AHR.

evolutionary biology↗

bioRxiv2017

Uneven Data Quality and the Earliest Occupation of Europe: The Case of Untermassfeld (Germany)

The database regarding the earliest occupation of Europe has increased significantly in quantity and quality of data points over the last two decades, mainly through the addition of new sites as a result of long-term systematic excavations and large-scale prospections of Early and early Middle Pleistocene exposures. The site distribution pattern suggests an ephemeral presence of hominins in the south of Europe from around one million years ago, with occasional short northward expansions along the western coastal areas when temperate conditions permitted. From around 600,000-700,000 years ago Acheulean artefacts appear in Europe and somewhat later hominin presence seems to pick up, with more sites and now some also present in colder climatic settings. It is again only later, around 350,000 years ago, that the first sites show up in more continental, central parts of Europe, east of the Rhine. A series of recent papers on the Early Pleistocene palaeontological site of Untermassfeld (Germany) makes claims that are of great interest for studies of earliest Europe and are at odds with the described pattern: the papers suggest that Untermassfeld has yielded stone tools and humanly modified faunal remains, evidence for a one million years old hominin presence in European continental mid-latitudes, and additional evidence that hominins were well-established in Europe already around that time period. Here we evaluate these claims and demonstrate that these studies are severely flawed in terms of data on provenance of the materials studied and in the interpretation of faunal remains and lithics as testifying to a hominin presence at the site. In actual fact any reference to the Untermassfeld site as an archaeological one is unwarranted. Furthermore, it is not the only European Early Pleistocene site where inferred evidence for hominin presence is problematic. The strength of the spatiotemporal patterns of hominin presence and absence depend on the quality of the data points we work with, and data base maintenance, including critical evaluation of new sites, is crucial to advance our knowledge of the expansions and contractions of hominin ranges during the Pleistocene.

paleontology↗