Hominid Species Research Articles

Morphometric Tomographic Analysis of the Head of the Tridactyl Humanoid Specimen from Nasca-Peru

Objective: To report the tomographic and morphometric analysis of the head of the tridactyl humanoid specimen from Nazca, Peru. Method: A qualitative case study approach. RadiAnt DICOM Viewer software version 4.2.1 was used to analyze lengths, diameters, and volume in tomographic images of the head. The morphological biometric analysis applied anthropometric methods using some craniometric points and cephalometric angles. Results and Discussion: As a result, it is reported that there are atypical, strange, and exceptional morphometric imaging features in the cephalic segment of specimen M01. The cephalometric analysis based on the ANB angle revealed a class II skeletal pattern, and according to the Bjorl-Jarabak analysis, it has a convex facial profile with hypodivergent growth (brachyfacial). The patient also has maxillary biprotrusion, severe protrusion of upper and lower incisors, loss of teeth, presence of root remnants, severe dental abrasion, non-assessable canine class, absence of three third molars and ocular protrusion. Based on craniometric points, the SNA angle (Sella, Nasion and Point A) and the SNB angle (Sella, Nasion and Point B) maxillary protrusion and mandibular protrusion were diagnosed. Implications of the research: It is concluded that the combination of uncommon morpho-anatomical features in the maxillofacial and cranial massif do not correspond to a human craniofacial biotype, but could be considered as suggestive findings of morpho-anatomical features typical of a hominid species similar to humans. Originality/Value: The expansion of biometric and morphoanatomical data of the head reinforces the hypothesis that morphologically it would be a non-human hybrid species.

Phylo-Epigenetics in Phylogeny Analyses and Evolution.

Long-standing, continuous blurring and controversies in the field of phylogenetic interspecies relations, associated with insufficient explanations for dynamics and variability of speeds of evolution in mammals, hint at a crucial missing link. It has been suggested that transgenerational epigenetic inheritance and the concealed mechanisms behind play a distinct role in mammalian evolution. Here, a comprehensive sequence alignment approach in hominid species, i.e., Homo sapiens, Homo neanderthalensis, Denisovan human, Pan troglodytes, Pan paniscus, Gorilla gorilla, and Pongo pygmaeus, comprising conserved CpG islands of housekeeping genes, uncover evidence for a distinct variability of CpG dinucleotides. Applying solely these evolutionary consistent and inconsistent CpG sites in a classic phylogenetic analysis, calibrated by the divergence time point of the common chimpanzee (P. troglodytes) and the bonobo or pygmy chimpanzee (P. paniscus), a "phylo-epigenetic" tree has been generated, which precisely recapitulates branch points and branch lengths, i.e., divergence events and relations, as they have been broadly suggested in the current literature, based on comprehensive molecular phylogenomics and fossil records of many decades. It is suggested here that CpG dinucleotide changes at CpG islands are of superior importance for evolutionary developments. These changes are successfully inherited through the germ line, determining emerging methylation profiles, and they are a central component of transgenerational epigenetic inheritance. It is hidden in the DNA, what will happen on it later.

Phylogenetic differences in the morphology and shape of the central sulcus in great apes and humans: implications for the evolution of motor functions.

The central sulcus divides the primary motor and somatosensory cortices in many anthropoid primate brains. Differences exist in the surface area and depth of the central sulcus along the dorso-ventral plane in great apes and humans compared to other primate species. Within hominid species, there are variations in the depth and aspect of their hand motor area, or knob, within the precentral gyrus. In this study, we used post-image analyses on magnetic resonance images to characterize the central sulcus shape of humans, chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla), and orangutans (Pongo pygmaeus and Pongo abelii). Using these data, we examined the morphological variability of central sulcus in hominids, focusing on the hand region, a significant change in human evolution. We show that the central sulcus shape differs between great ape species, but all show similar variations in the location of their hand knob. However, the prevalence of the knob location along the dorso-ventral plane and lateralization differs between species and the presence of a second ventral motor knob seems to be unique to humans. Humans and orangutans exhibit the most similar and complex central sulcus shapes. However, their similarities may reflect divergent evolutionary processes related to selection for different positional and habitual locomotor functions.

Tempo and mode of gene expression evolution in the brain across primates.

Primate evolution has led to a remarkable diversity of behavioral specializations and pronounced brain size variation among species (Barton, 2012; DeCasien and Higham, 2019; Powell et al., 2017). Gene expression provides a promising opportunity for studying the molecular basis of brain evolution, but it has been explored in very few primate species to date (e.g. Khaitovich et al., 2005; Khrameeva et al., 2020; Ma et al., 2022; Somel et al., 2009). To understand the landscape of gene expression evolution across the primate lineage, we generated and analyzed RNA-seq data from four brain regions in an unprecedented eighteen species. Here, we show a remarkable level of variation in gene expression among hominid species, including humans and chimpanzees, despite their relatively recent divergence time from other primates. We found that individual genes display a wide range of expression dynamics across evolutionary time reflective of the diverse selection pressures acting on genes within primate brain tissue. Using our samples that represent a 190-fold difference in primate brain size, we identified genes with variation in expression most correlated with brain size. Our study extensively broadens the phylogenetic context of what is known about the molecular evolution of the brain across primates and identifies novel candidate genes for the study of genetic regulation of brain evolution.

Bigfoot: If it's there, could it be a bear?

AbstractIt has been suggested that the American black bear (Ursus americanus) may be responsible for a significant number of purported sightings of an alleged unknown species of hominid in North America. Previous analyses have identified a correlation between ‘sasquatch’ or ‘bigfoot’ sightings and black bear populations in the Pacific Northwest using ecological niche models and simple models of expected animal sightings. The present study expands the analysis to the entire US and Canada by modelling sasquatch sightings and bear populations in each state/province while adjusting for human population and forest area in a generalized linear model. Sasquatch sightings were statistically significantly associated with bear populations such that, on the average, every bear increase in the bear population is associated with a ( CI: –) increase in sasquatch sightings. Thus, as black bear populations increase, sasquatch sightings are expected to increase. On average, across all states and provinces in 2006, after controlling for human population and forest area, there were approximately bears per sasquatch sighting. Based on statistical considerations, it is likely that many supposed sasquatch are really misidentified known forms. If bigfoot is there, it could be a bear.

Some Eschatological Perspectives on the Loss of Biodiversity and Extinction

Abstract This article explores the loss of biodiversity and species extinction from the perspective of Christian eschatology and, more specifically, the hope for eternal life. A thought experiment on the coexistence of various hominid and hominin species is entertained in order to gain some clarity on the nature of the problems posed by extinction. The question is then raised whether any of the traditional eschatological symbols of the reign of God, a final judgment, the resurrection of the dead, or eternal life can be retrieved to address the problems posed by extinction. It is argued that each of these symbols poses serious difficulties in this regard while there is an apparent contradiction embedded in the notion of eternal life. This is not resolved through notions of ‘objective immortality,’ as this by itself eternalizes the injustices of history. With Joseph Sittler, it is argued that only some notion of cosmic redemption can suffice, but how this is to be imagined remains elusive.

A reassessment of the distinctiveness of dryopithecine genera from the Iberian Miocene based on enamel-dentine junction geometric morphometric analyses.

A vast diversity of catarrhines primates has been uncovered in the Middle to Late Miocene (12.5-9.6Ma) of the Vallès-Penedès Basin (northeastern Spain), including several hominid species (Pierolapithecus catalaunicus, Anoiapithecus brevirostris, Dryopithecus fontani, Hispanopithecus laietanus, and Hispanopithecus crusafonti) plus some remains attributed to 'Sivapithecus' occidentalis (of uncertain taxonomic validity). However, Pierolapithecus and Anoiapithecus have also been considered junior synonyms of Dryopithecus by some authors, which entail a lower generic diversity and an inflated intrageneric variation of the latter genus. Since the distinction of these taxa partly relies on dental features, the detailed and quantitative analysis of tooth shape might help disentangling the taxonomic diversity of these Miocene hominids. Using diffeomorphic surface matching and three-dimensional geometric morphometrics, we investigate the enamel-dentine junction shape (which is a reliable taxonomic proxy) of these Miocene hominids, with the aim of investigating their degree of intra- and intergeneric variation compared with that of extant great ape genera. We conducted statistical analyses, including between-group principal component analyses, canonical variate analyses, and permutation tests, to investigate whether the individual and combined (i.e., Dryopithecus s.l.) variation of the extinct genera exceeds that of the extant great apes. Our results indicate that Pierolapithecus, Anoiapithecus, Dryopithecus, and Hispanopithecus show morphological differences of enamel-dentine junction shape relative to the extant great apes that are consistent with their attribution to different genera. Specifically, the variation displayed by the Middle Miocene taxa combined exceeds that of extant great ape genera, thus undermining the single-genus hypothesis. 'Sivapithecus' occidentalis specimens fall close to Dryopithecus but in the absence of well-preserved comparable teeth for Pierolapithecus and Anoiapithecus, their taxonomic attribution remains uncertain. Among the Hispanopithecus sample, IPS1802 from Can Llobateres stands out and might either be an outlier in terms of morphology, or represent another dryopithecine taxon.

Pattern and Form

This article explores the role of evolved pattern recognition in the development and divergence of mental frameworks underlying creative and metaphysical thought in Hominid species. It examines the emergence of figurative artistic expression through the lenses of Darwinian evolutionary theory and Gaboran honing theory, testing the limits and overlap of these methodologies when applied to humanity’s archaic relatives. This is contrasted with complex philosophical and artistic traditions of a relatively recent human society, Early Modern Persia. There is something of a taboo around the application of evolutionary psychology in some sociological circles due to its frequent misuse in pop science to dismiss societal change: an appeal to antiquity rebranded as biological determinism. This article will expand the use of evolutionary psychological methodologies in moderation as an additional tool in the study of archaic humanity and its relatives. It finds there is an evolutionary substratum to the development of creative thought, but that its recognisable features for a modern human were unlikely to have initially been selected traits themselves: this evolutionary substratum is a basis of sensory and conceptual pattern recognition traits, generating a mental atmosphere conducive to the development of collective strata of conceptual association, and is traceable to prehistory.

Raman Spectroscopy and STR Analysis of the Elongated Skulls from the Paracas Mummies of Peru

Between 1880-1947, several hundred mummified bodies were excavated from burial sites in the Paracas peninsula of Peru. Each set of recovered remains displayed reduced stature and severe cranial elongation, which led many anthropologists and archaeologists to question the genetic origins of what would be colloquially referred to as the “Cone Head mummies.” Since the discovery of these bodies, suggestions have been made that the mummies’ cranial deformations point to another human species, an unknown hominid species, or even within some groups, an alien. This project sought to employ commonly used forensic techniques, including but not limited to Raman spectroscopy and DNA fingerprinting, to investigate the hair structure and genetic profile from tissue and hair samples derived from the Paracas skulls. Tissue and hair samples were subjected to comparative hair analysis, Raman spectroscopy, and DNA typing using short tandem repeat (STR) analysis. Comparative microscopic hair analysis and Raman spectroscopy of samples collected from the Paracas skull as well as from humans of varying ethnicities revealed very similar hair structures and characteristics that are associated with human hairs. Following DNA extraction and amplification of tissue samples, STR typing results demonstrated allelic profiles similar and consistent with those DNA profiles observed in modern human populations. Moreover, no foreign DNA or unusual patterns/profiles were observed in any of the samples tested. Data generated to this point strongly suggest that the Paracas mummies are of the same species as humans and not from an unknown hominid or alien society.

Teeth, prenatal growth rates, and the evolution of human-like pregnancy in later Homo

Evidence of how gestational parameters evolved is essential to understanding this fundamental stage of human life. Until now, these data seemed elusive given the skeletal bias of the fossil record. We demonstrate that dentition provides a window into the life of neonates. Teeth begin to form in utero and are intimately associated with gestational development. We measured the molar dentition for 608 catarrhine primates and collected data on prenatal growth rate (PGR) and endocranial volume (ECV) for 19 primate genera from the literature. We found that PGR and ECV are highly correlated (R2 = 0.93, P < 0.001). Additionally, we demonstrated that molar proportions are significantly correlated with PGR (P = 0.004) and log-transformed ECV (P = 0.001). From these correlations, we developed two methods for reconstructing PGR in the fossil record, one using ECV and one using molar proportions. Dental proportions reconstruct hominid ECV (R2 = 0.81, P < 0.001), a result that can be extrapolated to PGR. As teeth dominate fossil assemblages, our findings greatly expand our ability to investigate life history in the fossil record. Fossil ECVs and dental measurements from 13 hominid species both support significantly increasing PGR throughout the terminal Miocene and Plio-Pleistocene, reflecting known evolutionary changes. Together with pelvic and endocranial morphology, reconstructed PGRs indicate the need for increasing maternal energetics during pregnancy over the last 6 million years, reaching a human-like PGR (i.e., more similar to humans than to other extant apes) and ECV in later Homo less than 1 million years ago.

Heterochronies and allometries in the evolution of the hominid cranium: a morphometric approach using classical anthropometric variables.

This article studies the evolutionary change of allometries in the relative size of the two main cranial modules (neurocranium and splanchnocranium) in the five living hominid species and a diverse sample of extinct hominins. We use six standard craniometric variables as proxies for the length, width and height of each cranial module. Factor analysis and two-block partial least squares (2B-PLS) show that the great apes and modern humans share a pervasive negative ontogenetic allometry in the neurocranium and a positive one in the splanchnocranium. This developmental constraint makes it possible to interpret the cranial heterochronies in terms of ontogenetic scaling processes (i.e., extensions or truncations of the ancestral ontogenetic trajectory) and lateral transpositions (i.e., parallel translations of the entire trajectory starting from a different shape for a given cranial size). We hypothesize that ontogenetic scaling is the main evolutionary modality in the australopithecines while in the species of Homo it is also necessary to apply transpositions. Both types of processes are coordinated in Homo, which result in an evolutionary trend toward an increase in brain size and in the degree of paedomorphosis from the earliest habilines.

The Battle Rages On

The Battle Rages On

Are There Differences in the Cranial Base of Humans and Apes?

Differences in skull-base angles between humans, other hominid species and apes might account for the ability of humans to develop complex speech. This study compared midline skull base angles, and angles related to insertion of skull base musculature between these species. 126 human adult, 29 adolescent, 19 children, and 13 fetus skulls were compared to 32 ape and a subset of non-human antiquity hominid casts of skulls (13). Cranial base measurements were taken using an eMicroscribe 3d G2 digitizer. Midline and muscle insertion measurements were obtained. There were statistical differences in both the midline angles of the skull base (humans, 119o; apes, 130o) and in the Skull base angles related to points of muscle insertion (humans, 113o; apes, 124o), with humans exhibiting a more acute angle than the apes and other non-human hominids. There were no differences between human adults and children CONCLUSION: Acute angle differentiation of the midline skull base between humans and apes was confirmed with an alternate measurement method. Whether these angular differences are the primary reason for the lower position of the larynx in humans and the potential for more complex speech is still in debate.

On the morphology and failure of worn human molar cusps

ObjectivesEnamel wear is a common occurrence that may lead to tooth failure. Beyond reducing enamel thickness, wear exposes different regions of enamel microstructure to various types of stresses. This work was aimed at elucidating the effect of enamel wear on enamel morphology and tooth resilience in human molar teeth undergoing large-scale contact. MethodsIntact/polished molar cusps were indented with a hard disk/ball. The unloaded specimens were sectioned longitudinally or transversely, and the damage examined by optical and scanning electron microscopy. The onset of cracks at the dentin horn apex was determined by a FEM stress analysis that modeled a cusp as truncated, conical enamel shell supported by dentin. ResultsThe damage consisted of radial and cylindrical cracks growing under the contact, sparsely distributed radial cracks in the enamel shell region, and cracking from tufts at the dentin horn apex (TA cracks). The damage under the contact circle exhibited shear deformation zones. These zones helped relieve contact stresses, absorb energy, contain damage, and solicit cylindrical cracks in order to avoid growth of wear-sensitive cone cracks. Enamel tufts provided stress shielding while Hunter-Schreger Bands helped maintain this benefit by enforcing a collaborative cracking. The TA cracks were deemed a primary cause for tooth failure. The FEA predicted well the onset of these cracks. Making use of in vivo enamel wear data, the analysis showed that cusp failure might routinely occur at old age. SignificanceThe results provided new information on the response of the interior part of enamel to contact loading. This included the resistant effects of the waviness of enamel rods, interrods and tufts. The unique microstructure of enamel gave rise to shear bands under the contact circle that helped relieve contact stresses, absorb energy and contain damage. Enamel interrods solicited cylindrical cracking in order to avoid the wear-sensitive cone cracks. The onset of cracks at the dentin horn apex (TA cracks) was deemed critical to a tooth survival. The FEA showed that this cracking mode might routinely occur at old age due to natural enamel wear. Finally, the occlusal force needed to initiate the TA cracks in intact cusps can help explain the natural design logic involving the maximum bite force of hominid species.

N.R.C. C.A.A. and the Changing Concept of Identity in Indian Perspective

Migrations of tribe, people, race from one place to another for socio-economic-political reasons are as old as evolution of human race. According to archeologists, the first hominid species originated from Africa had been migrated to all over the globe. However in modern era, migrants from one country to another withoutproper documents and legal process are characterized as “Illegal immigrants.” In 1947 A.D. the Indian Sub-continent had been broken in-to two separate Nation State of India and Pakistan as part of decolonization process from almost two century old British colonial regime. Very huge quantities of people had to migrate from both these two lands. The Indian Constitution had made provisions to provide Indian citizenship to the migrants through legal process. To determine who genuine Indian citizens were, the N.R.C. was first prepared in 1951. It was decided that migrants from Pakistan will be given Indian citizenship till the first January, 1966. However during the 1970s, Liberation war had been fought between Pakistan army and Bengali speaking resident of East Pakistan supported by Indian Govt. In this period, large amount of migrants from East Pakistan had been entered in different Indian provinces for economic-political stability. According to the book “Bangladesh Ke swatantra Sangram Mein Bharat Ka Yugdaan” authored by salaam Azad, the migrant no was 9899 305. After establishment of Bangladesh in 1971, Mujib Treaty was signed between India and the new Country. Indian Govt agreed to provide citizenship to all Bangladeshi migrant residing in Assam till 24.3.1971. The Assam accord signed by the Indian Govt. and Assam’s ethnic associations cemented the agreement. However during the last three decades illegal migration from Bangladesh to Assam had been increased rapidly. Out of 33 districts of Assam, 9 have been over crowded with these Bangladeshi illegal immigrants. This changed demography of these districts and native ethnic –religious groups became minorities in their forefathers’ land. In 2012 a clash occurred between Bodo and Bangladeshi Muslims in the Bodoland territories in which more than 70 people had died. In this background, Assam Samhita Maha Sangh applied to Supreme Court for determining illegal migrants. In response, Indian Supreme Court ordered to update the N.R.C list in 2014.The process began in 2015. Out of 3.29 Corer applicants, 2.89 Cores have made to included themselves into the updated list. In 2016, the Indian govt. introduced Citizenship Ammendment Bill in house Of the People with the aim of providing Indian citizenship to Hindu, Sikh,Parsi, Christian, Jain and Buddhist illegal immigrants from Afganistan, Bangladesh and Pakistan. However this acts this facing criticism and protest from both opposition Indian political parties besides common masses. Several opposing party spoke person labeled this act and process as communal and anti-Muslim in nature. Besides, political parties, common people created mass protests against amendment of Indian citizenship through offline and online platform. In Sheen Bag, Delhi Muslim womenfolk actively protested. They set up community kitchen, political discourse arena, public library etc. This model was followed by other regional centers of protest through all over India. It is my aim in this essay to analyze changing concept of Indian people’s legal and political identity on the background of N.R.C, C.A.A. I will use both primary and secondary sources

Lethal coalitionary attacks of chimpanzees (Pan troglodytes troglodytes) on gorillas (Gorilla gorilla gorilla) in the wild

Intraspecies violence, including lethal interactions, is a relatively common phenomenon in mammals. Contrarily, interspecies violence has mainly been investigated in the context of predation and received most research attention in carnivores. Here, we provide the first information of two lethal coalitionary attacks of chimpanzees (Pan troglodytes troglodytes) on another hominid species, western lowland gorillas (Gorilla gorilla gorilla), that occur sympatrically in the Loango National Park in Gabon. In both events, the chimpanzees significantly outnumbered the gorillas and victims were infant gorillas. We discuss these observations in light of the two most widely accepted theoretical explanations for interspecific lethal violence, predation and competition, and combinations of the two-intraguild predation and interspecific killing. Given these events meet conditions proposed to trigger coalitional killing of neighbours in chimpanzees, we also discuss them in light of chimpanzees’ intraspecific interactions and territorial nature. Our findings may spur further research into the complexity of interspecies interactions. In addition, they may aid in combining field data from extant models with the Pliocene hominid fossil record to better understand behavioural adaptations and interspecific killing in the hominin lineage.

Assessing complexity in hominid dental evolution: Fractal analysis of great ape and human molars.

Molar crenulation is defined as the accessory pattern of grooves that appears on the occlusal surface of many mammalian molars. Although frequently used in the characterization of species, this trait is often assessed qualitatively, which poses unavoidable subjective biases. The objective of this study is to quantitatively test the variability in the expression of molar crenulation in primates and its association with molar size and diet. The variability in the expression of molar crenulation in hominids (human, chimpanzee, gorilla, and orangutan) was assessed with fractal analysis using photographs of first, second and third upper and lower molars. After this, representative values for 29 primate species were used to evaluate the correlation between molar complexity, molar size, and diet using a phylogenetic generalized least squares regression. Results show that there are statistically significant differences in fractal dimensions across hominid species in all molars, with orangutan molars presenting higher values of occlusal complexity. Our results indicate that there is no significant association between molar complexity and molar size or diet. Our results show higher levels of occlusal complexity in orangutans, thus supporting previously published observations. Our analyses, however, do not indicate a clear association between molar complexity and molar size or diet, pointing to other factors as the major drivers of complexity. To our knowledge, our study is the first one to use fractal analysis to measure occlusal complexity in primates. Our results show that this approach is a rapid and cost-effective way to measure molar complexity.

Anthropogenesis and the Soul

The science of evolution acutely raises the perennial question of humankind’s place in the world. How does the theological anthropology of humans as imago Dei relate to an evolutionary anthropology with human beings derived from ancestral hominid species? Evolutionary biologists disclose ever greater similarities and continuity between animals and humans. Is human distinctiveness simply continuous with other ancestral forms of life or is there any kind of discontinuity? The answers to these questions depend not only on zoological considerations but also on one’s philosophy of nature. The standard anthropology within the Catholic Church is the dual-origin model: the human body originates through evolution, but the human soul is directly created by God. This formulation, however, is not without difficulties, primarily for its seeming Cartesian dualism of a body and soul as distinct substances. This paper develops the anthropology of David Braine who, drawing upon Aristotle, Thomas Aquinas, and Ludwig Wittgenstein, clearly situates humans as animals in great continuity with them. However, as linguistic animals who think in a medium of words, humans have a form of life—a soul—that transcends bodily processes. Braine’s anthropology provides a more coherent anthropology to understand the continuity and discontinuity of the human person in phylogenetic relationship to other species within an evolutionary perspective.

The position of Neandertal and Homo erectus within the hominid clade based on craniodental morphology and whole mtDNA genomes.

To evaluate the taxonomic position of the Neandertal and Homo erectus within the hominid clade, the variation among and within the hominid taxa was assessed based on the craniodental morphology and integrated with molecular analyses of the whole mtDNA genomes. Ordination and clustering of the Procrustes craniodental landmarks have showed a notable shape transformation from the earliest hominid species to the modern humans. Although levels of distinction between the analyzed taxa (Homo, Pan, Gorilla, and Pongo) are generally corresponding to probable expectations based on their taxonomic rank, few exceptions were found. Notably, the craniodental morphology of Homo erectus showed a greater dissimilarity to other Homo species, where it consistently overlapped or grouped with Pan species on all ordination plots and clustering. In addition, the direct link between European humans and Neandertals, which is well-characterized on all of the phylogenetic trees based on maximum parsimony and maximum likelihood methods, was not outlined in the morphologic-based clustering. Both morphological and molecular distances between Neandertal and modern humans were consistently greater than the distances among modern humans, however, the distances are still smaller than those between any two distinct species (so they are subspecies). The topology of the phylogenetic trees based on the whole mtDNA has shown a minor discrepancy with the results obtained from the craniodental morphologies.

Humans and Chimpanzees Display Opposite Patterns of Diversity in Arylamine N-Acetyltransferase Genes.

Among the many genes involved in the metabolism of therapeutic drugs, human arylamine N-acetyltransferases (NATs) genes have been extensively studied, due to their medical importance both in pharmacogenetics and disease epidemiology. One member of this small gene family, NAT2, is established as the locus of the classic human acetylation polymorphism in drug metabolism. Current hypotheses hold that selective processes favoring haplotypes conferring lower NAT2 activity have been operating in modern humans’ recent history as an adaptation to local chemical and dietary environments. To shed new light on such hypotheses, we investigated the genetic diversity of the three members of the NAT gene family in seven hominid species, including modern humans, Neanderthals and Denisovans. Little polymorphism sharing was found among hominids, yet all species displayed high NAT diversity, but distributed in an opposite fashion in chimpanzees and bonobos (Pan genus) compared to modern humans, with higher diversity in Pan species at NAT1 and lower at NAT2, while the reverse is observed in humans. This pattern was also reflected in the results returned by selective neutrality tests, which suggest, in agreement with the predicted functional impact of mutations detected in non-human primates, stronger directional selection, presumably purifying selection, at NAT1 in modern humans, and at NAT2 in chimpanzees. Overall, the results point to the evolution of divergent functions of these highly homologous genes in the different primate species, possibly related to their specific chemical/dietary environment (exposome) and we hypothesize that this is likely linked to the emergence of controlled fire use in the human lineage.