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Nasal airflow simulations suggest convergent adaptation in Neanderthals and modern humans

Significance Due to its role in humidifying and warming the air before it reaches the lungs, adaptations in the internal nasal anatomy are suspected to have been essential for modern humans and Neanderthals during the settlement of Eurasian harsh landscapes. Unfortunately, the lack of soft-tissue evidence in the fossil record precludes any study of Neanderthal respiratory performance. Here, we use warping techniques to reconstruct a generic Neanderthal nose, computational fluid dynamics simulations to compare the respiratory performance on both species, and evolutionary analyses to detect signals of selection. We report striking differences on fluid residence times under cold/dry climatic conditions. Different from previously suggested, our results indicate that both species would have achieved an advantageous species-specific respiratory performance in cold climates. Both modern humans (MHs) and Neanderthals successfully settled across western Eurasian cold-climate landscapes. Among the many adaptations considered as essential to survival in such landscapes, changes in the nasal morphology and/or function aimed to humidify and warm the air before it reaches the lungs are of key importance. Unfortunately, the lack of soft-tissue evidence in the fossil record turns difficult any comparative study of respiratory performance. Here, we reconstruct the internal nasal cavity of a Neanderthal plus two representatives of climatically divergent MH populations (southwestern Europeans and northeastern Asians). The reconstruction includes mucosa distribution enabling a realistic simulation of the breathing cycle in different climatic conditions via computational fluid dynamics. Striking across-specimens differences in fluid residence times affecting humidification and warming performance at the anterior tract were found under cold/dry climate simulations. Specifically, the Asian model achieves a rapid air conditioning, followed by the Neanderthals, whereas the European model attains a proper conditioning only around the medium-posterior tract. In addition, quantitative-genetic evolutionary analyses of nasal morphology provided signals of stabilizing selection for MH populations, with the removal of Arctic populations turning covariation patterns compatible with evolution by genetic drift. Both results indicate that, departing from important craniofacial differences existing among Neanderthals and MHs, an advantageous species-specific respiratory performance in cold climates may have occurred in both species. Fluid dynamics and evolutionary biology independently provided evidence of nasal evolution, suggesting that adaptive explanations regarding complex functional phenotypes require interdisciplinary approaches aimed to quantify both performance and evolutionary signals on covariation patterns.

Developmental pathways inferred from modularity, morphological integration and fluctuating asymmetry patterns in the human face

Facial asymmetries are usually measured and interpreted as proxies to developmental noise. However, analyses focused on its developmental and genetic architecture are scarce. To advance on this topic, studies based on a comprehensive and simultaneous analysis of modularity, morphological integration and facial asymmetries including both phenotypic and genomic information are needed. Here we explore several modularity hypotheses on a sample of Latin American mestizos, in order to test if modularity and integration patterns differ across several genomic ancestry backgrounds. To do so, 4104 individuals were analyzed using 3D photogrammetry reconstructions and a set of 34 facial landmarks placed on each individual. We found a pattern of modularity and integration that is conserved across sub-samples differing in their genomic ancestry background. Specifically, a signal of modularity based on functional demands and organization of the face is regularly observed across the whole sample. Our results shed more light on previous evidence obtained from Genome Wide Association Studies performed on the same samples, indicating the action of different genomic regions contributing to the expression of the nose and mouth facial phenotypes. Our results also indicate that large samples including phenotypic and genomic metadata enable a better understanding of the developmental and genetic architecture of craniofacial phenotypes.

Reply to Evteev and Heuzé: How to overcome the problem of modeling respiration departing from bony structures

Evteev and Heuze (1) state that there is no evidence supporting that Chinese, Japanese, and Korean populations exhibit cold-adaptation features. However, several facial traits present in these groups were previously interpreted as cold-climate adaptations (2⇓⇓⇓⇓⇓⇓–9). For instance, a composite sample that included Chinese, Japanese, and Korean individuals showed internal nasal variation compatible with theoretical expectations for cold climate adaptations (9). It is also noteworthy that we applied computational fluid dynamics (CFD) analyses that directly test for differences in the internal nasal mucosa, making irrelevant any prior difference among cold- versus warm-evolved populations. Such potential prior differences are also irrelevant in the context of Lande’s test, which departs from random … [↵][1]1To whom correspondence may be addressed. Email: rolando{at}cenpat-conicet.gob.ar or rodrigo.r.paz{at}gmail.com. [1]: #xref-corresp-1-1

Entailed Norms and the Systematization of Law

The validity within legal systems of entailed norms, that is, those norms that are logically derivable from explicitly issued rules, has been called into question with different arguments. To take two examples from distinguished figures, Joseph Raz has claimed that what he calls the “incorporation thesis” cannot account for law’s claim of authority, and Andrei Marmor believes that the admission of entailed norms in a legal system would imply the mistaken view that it is necessarily coherent. In this paper we show that these two arguments are, at the very least, highly controversial; that the positivist social sources thesis, though not committed to it, is compatible with the validity of entailed norms, and that taking into account the whole set of logical consequences of explicitly issued norms is an unavoidable step in explaining the dynamic character of legal systems .