Thyroid Hormone Signalling in Human Evolution and Disease: A Novel Hypothesis

Thyroid hormone (TH) signalling is a universally conserved pathway with pleiotropic actions that is able to control the development, metabolism, and homeostasis of organisms. Using evidence from paleoecology/palaeoanthropology and data from the physiology of modern humans, we try to assess the natural history of TH signalling and its role in human evolution. Our net thesis is that TH signalling has likely played a critical role in human evolution by facilitating the adaptive responses of early hominids to unprecedently challenging and continuously changing environments. These ancient roles have been conserved in modern humans, in whom TH signalling still responds to and regulates adaptations to present-day environmental and pathophysiological stresses, thus making it a promising therapeutic target.

Evaluating Non-STEM Students’ understanding of Evolution: Basis for designing Pedagogical Intervention

Teaching human evolution, for it to yield fruitful results, should be initialized by understanding the perspective of the learners. This study was conducted to aid in achieving that objective, and also to provide ways for educators to come up with strategies that can be perceived and appreciated by learners, particularly those who are not inclined with science. The majority of the respondents are believers in the theory of human evolution. Most of the respondents expressed their belief that modern humans are successors of ape-like organisms. The majority of the same set of informants mentioned their need for clarity about the stages that humans underwent during the course of history, while almost all of those respondents stated that the utilization of various graphic materials to elucidate these evolutionary concepts. It was recommended that educators engage in learning methods that call the attention and those that can be easily understood by the students

What Studying the Songs of a Distant Primate Relative Can Teach Us About Ourselves

Tarsiers are nocturnal animals. They have eyes that are heavier than their brains. They eat only insects and other living things. Tarsiers are primates, just like humans. And some species of tarsiers sing! Tarsier songs and human language are different in many ways. But if we study the similarities, it may help us better understand human language. In our study, we recorded singing tarsiers on the Indonesian island of Sulawesi. With the help of computers, we found that we could tell individual tarsiers apart based on their songs. Being able to recognize who is singing from far away may be an important function of tarsier songs. We also found that if a female speeds up her song, then the male speeds up his song, too. The ability to modify vocal output based on what others are doing is a universal in human language. Our results show that tarsiers (like humans) can change their vocalizations based on what their partner is doing. The fact that tarsiers and humans are both able to do this indicates that their common ancestor probably had this ability. Our results add support to the idea that flexibility in vocal interactions evolved long before the appearance of modern humans.

Domestication is not an ancient moment of selection for prosociality: Insights from dogs and modern humans

Domestication is often portrayed as a long-past event, at times even in archaeological literature. The term domestication is also now applied to other processes, including human evolution. In such contexts, domestication means selection for friendliness or prosociality and the bodily results of such selective choices. Both such perspectives are misleading. Using dogs and modern humans as entry points, this paper explores why conceiving of domestication as a threshold event consisting of selection for prosociality is both incomplete and inaccurate. Domestication is an ongoing process, not a moment or an achievement. Selection in breeding, including for prosociality, is a part of many domestication histories, but it alone does not sustain this process over multiple generations. Further, much selection in domestication has little to do with human intention. Care, taming, commensalism, material things, and places are critical in carrying domestic relationships forward.

The evolutionary history of human spindle genes includes back-and-forth gene flow with Neandertals

Proteins associated with the spindle apparatus, a cytoskeletal structure that ensures the proper segregation of chromosomes during cell division, experienced an unusual number of amino acid substitutions in modern humans after the split from the ancestors of Neandertals and Denisovans. Here, we analyze the history of these substitutions and show that some of the genes in which they occur may have been targets of positive selection. We also find that the two changes in the kinetochore scaffold 1 (KNL1) protein, previously believed to be specific to modern humans, were present in some Neandertals. We show that the KNL1 gene of these Neandertals shared a common ancestor with present-day Africans about 200,000 years ago due to gene flow from the ancestors (or relatives) of modern humans into Neandertals. Subsequently, some non-Africans inherited this modern human-like gene variant from Neandertals, but none inherited the ancestral gene variants. These results add to the growing evidence of early contacts between modern humans and archaic groups in Eurasia and illustrate the intricate relationships among these groups.

Archaic introgression and variation in pharmacogenes and implications for local adaptation

Modern humans carry Neanderthal and Denisovan (archaic) genome elements which may have been a result of environmental adaptation. These effects may be particularly evident in pharmacogenes - genes responsible for the processing of exogenous substances such as food, pollutants, and medications. However, the health implications and contribution of archaic ancestry in pharmacogenes of modern humans remains understudied. We characterize eleven key cytochrome P450 (CYP450) genes involved in drug metabolizing reactions in three Neanderthal and one Denisovan individuals and examine archaic introgression in modern human populations. We infer the metabolizing efficiency of these eleven genes in archaic individuals and show important genetic differences relative to modern human variants. We identify archaic-specific SNVs in each CYP450 gene, including some that are potentially damaging, which may result in altered metabolism in modern human people carrying these variants. We highlight four genes which display interesting patterns of archaic variation: CYP2B6 - we find a large number of unique variants in the Vindija Neanderthal, some of which are shared with a small subset of African modern humans; CYP2C9 - containing multiple variants that are shared between Europeans and Neanderthals; CYP2A6*12 - a variant defined by a hybridization event that was found in humans and Neanderthals, suggesting the recombination event predates both species; and CYP2J2 - in which we hypothesize a Neanderthal variant was re-introduced in non-African populations by archaic admixture. The genetic variation identified in archaic individuals imply environmental pressures that may have driven CYP450 gene evolution.