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Organisms perceive their environment and respond. The origin of perception-response traits presents a puzzle. Perception provides no value without response. Response requires perception. Recent advances in machine learning may provide a solution. A randomly connected network creates a reservoir of perceptive information about the recent history of environmental states. In each time step, a relatively small number of inputs drives the dynamics of the relatively large network. Over time, the internal network states retain a memory of past inputs. To achieve a functional response to past states or to predict future states, a system must learn only how to match states of the reservoir to the target response. In the same way, a random biochemical or neural network of an organism can provide an initial perceptive basis. With a solution for one side of the two-step perception-response challenge, evolving an adaptive response may not be so difficult. Two broader themes emerge. First, organisms may often achieve precise traits from sloppy components. Second, evolutionary puzzles often follow the same outlines as the challenges of machine learning. In each case, the basic problem is how to learn, either by artificial computational methods or by natural selection.

The editors to this volume posed a series of fascinating questions relating to how seeing compassion as a skill can help us understand its nature, cultivation and effects within secular contexts. This paper addresses these questions by comparing evolutionary with contemplative approaches to compassion. Recent scientific approaches have explored the evolved roots and biopsychosocial manifestations of compassion and their impact on mental states and prosocial behaviour, particularly in regard to both its facilitators and inhibitors. In contrast, we discuss how the contemplative traditions have approached the origins and cultivation of compassion through observing the mind (e.g. meditation), with a focus on gaining insight into self-transcendent experiences, the nature of inter-connectivity and non-separate existence (also referred to as non-duality), through which compassion arises naturally. Both evolutionary and contemplative perspectives have the same focus which is to understand and prevent the causes of suffering, including the suffering we cause ourselves because of our harmful potentials. However, in terms of training the mind in compassion skills, this paper considers how training approaches linked to the evolutionary model often use thinking, empathising, reflecting and guided behaviour change to activate psychophysiological systems linked to caring and compassion. In contrast, the contemplative traditions focus less on thinking and reflecting and more on creating conditions for direct experiencing. A key reason for doing so is to settle the mind so that subtler levels of consciousness can enable the experience of self-transcendent compassion to arise. Thus, both evolutionary and contemplative approaches can focus on developing mind awareness and the importance of practise, but evolutionary approaches such as compassion focused therapy do not pursue transcendent wisdoms or insights. [ABSTRACT FROM AUTHOR]

In recent years, the explanatory term "scaffold" has been gaining prominence in evolutionary biology. This notion has a long history in other areas, in particular, developmental psychology. In this paper, we connect these two traditions and identify a specific type of explanatory strategy shared between them, namely scaffolding explanations. We offer a new definition of "scaffold" anchored in the explanatory practices of evolutionary biologists and developmental psychologists that has yet to be clearly articulated. We conclude by offering a systematic overview of the various dimensions of scaffolding explanations that further suggests both their usefulness and range of application. [ABSTRACT FROM AUTHOR]

Organisms perceive their environment and respond. The origin of perception–response traits presents a puzzle. Perception provides no value without response. Response requires perception. Recent advances in machine learning may provide a solution. A randomly connected network creates a reservoir of perceptive information about the recent history of environmental states. In each time step, a relatively small number of inputs drives the dynamics of the relatively large network. Over time, the internal network states retain a memory of past inputs. To achieve a functional response to past states or to predict future states, a system must learn only how to match states of the reservoir to the target response. In the same way, a random biochemical or neural network of an organism can provide an initial perceptive basis. With a solution for one side of the two-step perception–response challenge, evolving an adaptive response may not be so difficult. Two broader themes emerge. First, organisms may often achieve precise traits from sloppy components. Second, evolutionary puzzles often follow the same outlines as the challenges of machine learning. In each case, the basic problem is how to learn, either by artificial computational methods or by natural selection.

Sacrificing body parts is one of many behaviors that animals use to escape predation. This trait, termed autotomy, is classically associated with lizards. However, several other taxa also autotomize, and this trait has independently evolved multiple times throughout Animalia. Despite having multiple origins and being an iconic antipredatory trait, much remains unknown about the evolution of autotomy. Here, we combine morphological, behavioral, and genomic data to investigate the evolution of autotomy within leaf‐footed bugs and allies (Insecta: Hemiptera: Coreidae + Alydidae). We found that the ancestor of leaf‐footed bugs autotomized and did so slowly; rapid autotomy (<2 min) then arose multiple times. The ancestor likely used slow autotomy to reduce the cost of injury or to escape nonpredatory entrapment but could not use autotomy to escape predation. This result suggests that autotomy to escape predation is a co‐opted benefit (i.e., exaptation), revealing one way that sacrificing a limb to escape predation may arise. In addition to identifying the origins of rapid autotomy, we also show that across species variation in the rates of autotomy can be explained by body size, distance from the equator, and enlargement of the autotomizable appendage. [ABSTRACT FROM AUTHOR]

Biology and Neuroscience are addressing issues related to moral sentiments, but this does not mean that Philosophy has lost its importance in the debate. Paradoxically, the discovery that moral sentiments have evolutionary origins does not overcome the problem of “Hume’s Guillotine”. There are human characteristics which can be explained by natural selection and that are nonetheless culturally reproved. In order to choose or select which “natural” characteristics are to be promoted and which are to be discouraged, it is necessary to use a criterion that is not given by nature, although human capacities to discuss these criteria have been naturally shaped.

The repeated evolution of herbicide resistance in weeds is an ongoing problem in agricultural regions across the world, and presents a unique system in which to study the origins and spread of adaptive traits across heterogeneous landscapes. Lolium perenne ssp. multiflorum (Lam.) (Italian ryegrass) is a widespread grass weed of agricultural crops that has repeatedly evolved resistance to herbicides across the world. In California, resistance to glyphosate has become increasingly common. To identify the mechanisms conferring glyphosate resistance in California populations of L. perenne and to gain insights into the evolutionary origins and spread of resistance in the region, we investigated the frequency of target-site mutations conferring resistance to glyphosate combined with the frequency of resistant individuals in 14 populations. A region of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) was sequenced in 401 individuals to assay for target site mutations. Seven unique alleles were detected at codon site 106, four of which have been previously shown to confer target-site-based resistance to glyphosate. Four different resistance alleles were detected, indicating that resistance to glyphosate has evolved multiple times in the region. In two populations, no EPSPS mutations were detected despite the presence of resistant plants, strongly suggesting that non-target-site-based mechanisms confer resistance to glyphosate in these populations. It is likely that resistance to glyphosate in these 14 California populations of L. perenne derives from at least five evolutionary origins, indicating that adaptive traits can evolve repeatedly over agricultural landscapes.

The Jehol fauna was initially represented by a bony fish, concostracan and an insect, as a Lycoptera davidi-Eosestheria-Ephemeropsis trisetalis association, but since the researches of recent decades, the Jehol Biota is now completely different from the past low-diversity, and encompasses a native terrestrial biota that includes many well-preserved vertebrates, invertebrates and plants. There are more than 20 important biological categories, thousands of taphonomically unusual fossils, especially noted for the wide variety of biological tissues. The Jehol Biota has caused a sensation in the world with its wide distribution, large quantity, great variety, fine preservation and detailed information, which records the rise and fall of the numerous taxa, and provides significant evidence for three origins: of birds, eutherian mammals, and angiosperms. The Jehol Biota is a highlight of basic scientific research in China, and we honor it as a world-class fossil treasury and 'a Mesozoic Pompeii'. [ABSTRACT FROM AUTHOR]

The repeated evolution of herbicide resistance in weeds is an ongoing problem in agricultural regions across the world, and presents a unique system in which to study the origins and spread of adaptive traits across heterogeneous landscapes. Lolium perenne ssp. multiflorum (Lam.) (Italian ryegrass) is a widespread grass weed of agricultural crops that has repeatedly evolved resistance to herbicides across the world. In California, resistance to glyphosate has become increasingly common. To identify the mechanisms conferring glyphosate resistance in California populations of L. perenne and to gain insights into the evolutionary origins and spread of resistance in the region, we investigated the frequency of target-site mutations conferring resistance to glyphosate combined with the frequency of resistant individuals in 14 populations. A region of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) was sequenced in 401 individuals to assay for target site mutations. Seven unique alleles were detected at codon site 106, four of which have been previously shown to confer target-site-based resistance to glyphosate. Four different resistance alleles were detected, indicating that resistance to glyphosate has evolved multiple times in the region. In two populations, no EPSPS mutations were detected despite the presence of resistant plants, strongly suggesting that non-target-site-based mechanisms confer resistance to glyphosate in these populations. It is likely that resistance to glyphosate in these 14 California populations of L. perenne derives from at least five evolutionary origins, indicating that adaptive traits can evolve repeatedly over agricultural landscapes. [ABSTRACT FROM AUTHOR]

Ever since their appearance in the early 1990s, hypertext novels were presented as the pinnacle of digital aesthetics and claimed to represent the revolutionary future of literature. However, as a literary phenomenon, hypertext novels have remained marginal. The article presents some scientifically derived explanations as to why hypertext novels do not have a mass audience and why they are likely to remain a marginal contribution in the history of literature. Three explanatory frameworks are provided: (1) how hypertext relates to our cognitive information processing in general; (2) the empirically derived psychological reasons for how we read and enjoy literature in particular; and (3) the likely evolutionary origins of such a predilection for storytelling and literature. It is shown how hypertext theory, by ignoring such knowledge, has yielded misguided statements and uncorroborated claims guided by ideology rather than by scientifically supported knowledge. [ABSTRACT FROM AUTHOR]

How cooperation evolves in the presence of selfishness is a core problem in evolutionary biology. Selfish individuals tend to benefit themselves, which makes it harder to maintain cooperation between unrelated individuals and for living systems to evolve towards complex organizations. The general evolutionary model presented here identifies that non-kin selection is the root cause for cooperation between unrelated individuals and can enable and maintain higher complexity of biological organizations (the coexistence of more individuals of different types). The maintained number of genotypes within a cooperation organization is shown to follow a universal exponential law as a quantitative function of the population size and non-kin selection strength, showing a gene-pool-size invariance. Our results highlight that non-kin selection may be a hallmark of biological evolution, and play an important role in shaping life's potentials. [Display omitted] • Non-kin selection enhances complexity in a cooperation organization. • The number of genotypes maintained in a cooperation organization follows a universal exponential law. • The evolutionary model presented unifies cooperation between kin and non-kin. [ABSTRACT FROM AUTHOR]

Recent work in judgment and decision-making has shown that a good’s price can have irrational effects on people’s preferences. People tend to prefer goods that cost more money and assume that such expensive goods will be more effective, even in cases where the price of the good is itself arbitrary. Although much work has documented the existence of these pricing effects, unfortunately little work has addressed where these price effects come from in the first place. Here we use a comparative approach to distinguish between different accounts of this bias and to explore the origins of these effects. Specifically, we test whether brown capuchin monkeys (Cebus apella) are also susceptible to pricing effects within the context of an experimentally trained token economy. Using a capuchin population previously trained in a token market, we explored whether monkeys used price as an indicator of value across four experiments. Although monkeys demonstrated an understanding of which goods had which prices (consistently shifting preferences to cheaper goods when prices were increased), we observed no evidence that such price information affected their valuation of different kinds of goods. These results suggest that human price effects may involve more sophisticated human-unique cognitive capacities, such as an understanding of market forces and signaling.

Although play occurs in a wide variety of animals, models of the origins of play behavior are lacking. We propose a novel computational model exploring the evolution of non-social frivolous play. Asexually reproducing semelparous animals can either rest or forage. Foraging occurs when an organism is below an energy threshold. Success is determined by the combination of skill and availability of resources, which declines over time but replenishes for each generation. Play was introduced as a mutant strategy: a frivolous activity that uses energy and increases the probability of dying over resting with no direct fitness benefit. Simulations show that play behavior becomes fixed in the population and the time spent playing is maintained at a low rate in spite of its costly nature. When play behavior is functional by increasing foraging ability, it evolves quickly and the time individuals spend playing increases, but eventually the population of players collapses and play disappears. We suggest a mechanism underlying the origins of adaptive play from non-adaptive behavior when resources expand. Initially play acts as a spiteful behavior in that playing individuals suffer a direct cost to their fitness, but also may incur even greater costs to other individuals in the population. [ABSTRACT FROM AUTHOR]

Urochordates (ascidians) have recently supplanted cephalochordates (amphioxus) as the extant sister taxon of vertebrates. Given that urochordates possess migratory cells that have been classified as 'neural crest-like'- and that cephalochordates lack such cells - this phylogenetic hypothesis may have significant implications with respect to the origin of the neural crest and neural crest-derived skeletal tissues in vertebrates. We present an overview of the genes and gene regulatory network associated with specification of the neural crest in vertebrates. We then use these molecular data - alongside cell behaviour, cell fate and embryonic context - to assess putative antecedents (latent homologues) of the neural crest or neural crest cells in ascidians and cephalochordates. Ascidian migratory mesenchymal cells - non-pigment-forming trunk lateral line cells and pigment-forming 'neural crest-like cells' (NCLC) - are unlikely latent neural crest cell homologues. Rather, Snail-expressing cells at the neural plate of border of urochordates and cephalochordates likely represent the extent of neural crest elaboration in non-vertebrate chordates. We also review evidence for the evolutionary origin of two neural crest-derived skeletal tissues - cartilage and dentine. Dentine is a bona fide vertebrate novelty, and dentine-secreting odontoblasts represent a cell type that is exclusively derived from the neural crest. Cartilage, on the other hand, likely has a much deeper origin within the Metazoa. The mesodermally derived cellular cartilages of some protostome invertebrates are much more similar to vertebrate cartilage than is the acellular 'cartilage-like' tissue in cephalochordate pharyngeal arches. Cartilage, therefore, is not a vertebrate novelty, and a well-developed chondrogenic program was most likely co-opted from mesoderm to the neural crest along the vertebrate stem. We conclude that the neural crest is a vertebrate novelty, but that neural crest cells and their derivatives evolved and diversified in a step-wise fashion - first by elaboration of neural plate border cells, then by the innovation or co-option of new or ancient metazoan cell fates. [ABSTRACT FROM AUTHOR]

Background: Fungus farming is an unusual life style in insects that has evolved many times in the wood boring weevils named ‘ambrosia beetles’. Multiple occurrences of this behaviour allow for a detailed comparison of the different origins of fungus farming through time, its directionality, and possible ancestral states. We tested these hypotheses with a phylogeny representing the largest data set to date, nearly 4 kb of nucleotides from COI, EF-1α, CAD, ArgK, 28S, and 200 scolytine taxa. Results: Phylogenetic analyses using Bayesian or parsimony approaches placed the root of Scolytinae close to the tribe Scolytini and Microborus, but otherwise indicated low resolution at older nodes. More recent clades were well resolved, including ten origins of fungus farming. There were no subsequent reversals to bark or phloem feeding in the fungus farming clades. The oldest origin of fungus farming was estimated near 50 Ma, long after the origin of Scolytinae (100-120 Ma). Younger origins included the species rich Xyleborini, dated to 21 Ma. Sister group comparisons and test of independence between traits indicated that neither gregarious larval feeding nor regular inbreeding by sibling mating was strongly correlated with the origin of fungus farming. Conclusion: Origins of fungus farming corresponded mainly with two periods of global warming in the Cenozoic era, which were characterised by broadly distributed tropical forests. Hence, it seems likely that warm climates and expanding tropical angiosperm forests played critical roles in the successful radiation of diverse fungus farming groups. However, further investigation will likely reveal additional biological factors that promote fungus farming. [ABSTRACT FROM AUTHOR]

Risk is a central feature of political decision making. Prospect theory, an empirically correct theory of choice under risk that deals precisely with this condition, therefore seems to have much to offer political science. Prospect theory's central finding is that individuals' attitude toward risk depends on whether they face losses or gains. Confronting gains, individuals are risk averse in their decision making; confronting losses, they are risk accepting. Where do these preferences come from? Do they also hold for collective decision making? How can prospect theory help us to solve puzzles in political science? This article addresses these questions by discussing some advances in evolutionary biology, behavioural economics, psychology, neuro-economics and political science. The article shows that there is increasing evidence that prospect theory preferences have an evolutionary origin and that these preferences extend to collective decision making. Moreover, it demonstrates that political science can indeed gain from applying prospect theory, as insights from prospect theory help to solve puzzles such as why some governments pursue electorally risky welfare state reform but others do not. [ABSTRACT FROM AUTHOR]

I outline the debate in metaphysics between those who believe time is tensed and those who believe it is tenseless. I describe the terms in which this debate has been carried out, and the significance to it of ordinary tensed language and widespread common sense beliefs that time is tensed. I then outline a case for thinking that our intuitive beliefs about tense constitute an Adaptive Imaginary Representation (Wilson, in Biol Philos 5:37-62, ; Wilson, in Biol Philos 10:77-97, ). I also outline a case for thinking that our ordinary tensed beliefs and tensed language owe their tensed nature to its being adaptive to adopt a temporally self-locating perspective on reality. If these conclusions are right, then common sense intuitions and temporal language will be utterly misleading guides to the nature of temporal reality. [ABSTRACT FROM AUTHOR]

Many researchers have claimed that the emotion of disgust functions to protect us from disease. Although there have been several discussions of this hypothesis, none have yet reviewed the evidence in its entirety. The authors derive 14 hypotheses from a disease-avoidance account and evaluate the evidence for each, drawing upon research on pathogen avoidance in animals and empirical research on disgust. In all but 1 case, the evidence favors a disease-avoidance account. It is suggested that disgust is evoked by objects/people that possess particular types of prepared features that connote disease. Such simple disgusts are directly disease related, are acquired during childhood, and are able to contaminate other objects/people. The complex disgusts, which emerge later in development, may be mediated by several emotions. In these cases, violations of societal norms that may subserve a disease-avoidance function, notably relating to food and sex, act as reminders of simple disgust elicitors and thus generate disgust and motivate compliance. The authors find strong support for a disease-avoidance account and suggest that it offers a way to bridge the divide between concrete and ideational accounts of disgust. [ABSTRACT FROM AUTHOR]

Exploration is an initial phase of constructing spatial representation. In an illuminated environment, exploration by nocturnal rodents takes the form of home-base behavior, with the rodents organizing their activity in relation to the base, repeatedly orienting and returning to it. In the dark, home base behavior in gerbils is preceded by looping exploration, in which travel paths tangle into loops that close at various locations so that the gerbils pilot from one loop to the next. In the present study we tested a diurnal gerbil, the fat sand rat, Psammomys obesus, in both a lit and a dark open field in order to compare its exploratory behavior with that of nocturnal rodents. We found that under lit conditions, fat sand rats used perimeter patrolling, traveling mainly along the walls of the open field. In perimeter patrolling the animal probably monitors its location in relation to the perimeter (arena walls), and not to a specific location as in home base. In the dark, fat sand rats first used looping, and gradually shifted to perimeter patrolling exploration. We suggest that perimeter patrolling is a transient phase in which the animal evaluates possible locations for a home base. Thus, perimeter patrolling is an intermediate phase between looping, which is based on piloting from one landmark to the next, and home base exploration, in which the animal continuously orients to a specific location. This spatial behavior of perimeter patrolling may shed light on phases of information processing and spatial representation during exploration and navigation. [ABSTRACT FROM AUTHOR]

Although the technical problem-solving expertise of nonhuman primates has been investigated extensively in captivity, few species have been tested in their natural habitats. Here I examine the physical cognition of wild savanna baboons ( Papio anubis), a species that occupies an omnivorous foraging niche in which a variety of embedded food items are extracted and processed. Baboons were tested on three puzzles, each involving high-quality food that required removal from a novel obstruction: (1) a string-pulling puzzle in which food was hung from tree branches, (2) a twig-dipping puzzle in which food was embedded in a vertical tube, and (3) a stick-pushing puzzle in which food was contained in a horizontal conduit. The baboons failed to solve the second and third puzzles even when tools had been appropriately positioned in advance. And although they solved the first puzzle, their actions (running while holding food that was still attached to the string), suggested they did not fully comprehend the string’s connective property. The baboons’ performance might reflect the time constraints of life in the wild, which relative to captivity may provide fewer opportunities for the development of understanding about the physical properties of objects and their potential uses as tools. Further experiments on the physical cognition of baboons and many other primate species in their natural habitats would help test this ontogenetic hypothesis. Such field experiments would be especially fruitful if they continued to target extractive foragers like baboons: these experiments could simultaneously provide a test of phylogenetic hypotheses that invoke extractive foraging as the key stimulus for brain expansion in savanna-dwelling hominids. [ABSTRACT FROM AUTHOR]

Extreme animal movements are usually associated with a single, high-performance behavior. However, the remarkably rapid mandible strikes of the trap-jaw ant, Odontomachus bauri, can yield multiple functional outcomes. Here we investigate the biomechanics of mandible strikes in O. bauri and find that the extreme mandible movements serve two distinct functions: predation and propulsion. During predatory strikes, O. bauri mandibles close at speeds ranging from 35 to 64 m·s-1 within an average duration of 0.13 ms, far surpassing the speeds of other documented ballistic predatory appendages in the animal kingdom. The high speeds of the mandibles assist in capturing prey, while the extreme accelerations result in instantaneous mandible strike forces that can exceed 300 times the ant's body weight. Consequently, an O. bauri mandible strike directed against the substrate produces sufficient propulsive power to launch the ant into the air. Changing head orientation and strike surfaces allow O. bauri to use the trap-law mechanism to capture prey, eject intruders, or jump to safety. This use of a single, simple mechanical system to generate a suite of profoundly different behavioral functions offers insights into the morphological origins of novelties in feeding and locomotion. [ABSTRACT FROM AUTHOR]

Abstract: Escherichia coli express many types of O antigen, present in the outer membrane of the Gram-negative bacterial cell wall. O-Antigen biosynthesis genes are clustered together and differences seen in O-antigen types are due to genetic variation within this gene cluster. Sequencing of the E. coli O4 O-antigen gene cluster revealed a similar gene order and high levels of similarity to that of E. coli O26; indicating a common ancestor. These lateral transfer events observed within O-antigen gene clusters may occur as part of the evolution of the pathogenic clones. [Copyright &y& Elsevier]

The rapid accumulation of mutations in the SARS-CoV-2 Omicron variant that enabled its outbreak raises questions as to whether its proximal origin occurred in humans or another mammalian host. Here, we identified 45 point mutations that Omicron acquired since divergence from the B.1.1 lineage. We found that the Omicron spike protein sequence was subjected to stronger positive selection than that of any reported SARS-CoV-2 variants known to evolve persistently in human hosts, suggesting a possibility of host-jumping. The molecular spectrum of mutations (i.e., the relative frequency of the 12 types of base substitutions) acquired by the progenitor of Omicron was significantly different from the spectrum for viruses that evolved in human patients but resembled the spectra associated with virus evolution in a mouse cellular environment. Furthermore, mutations in the Omicron spike protein significantly overlapped with SARS-CoV-2 mutations known to promote adaptation to mouse hosts, particularly through enhanced spike protein binding affinity for the mouse cell entry receptor. Collectively, our results suggest that the progenitor of Omicron jumped from humans to mice, rapidly accumulated mutations conducive to infecting that host, then jumped back into humans, indicating an inter-species evolutionary trajectory for the Omicron outbreak., Competing Interests: Conflict of interest The authors declare that they have no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Recent work in judgment and decision-making has shown that a good's price can have irrational effects on people's preferences. People tend to prefer goods that cost more money and assume that such expensive goods will be more effective, even in cases where the price of the good is itself arbitrary. Although much work has documented the existence of these pricing effects, unfortunately little work has addressed where these price effects come from in the first place. Here we use a comparative approach to distinguish between different accounts of this bias and to explore the origins of these effects. Specifically, we test whether brown capuchin monkeys (Cebus apella) are also susceptible to pricing effects within the context of an experimentally trained token economy. Using a capuchin population previously trained in a token market, we explored whether monkeys used price as an indicator of value across four experiments. Although monkeys demonstrated an understanding of which goods had which prices (consistently shifting preferences to cheaper goods when prices were increased), we observed no evidence that such price information affected their valuation of different kinds of goods. These results suggest that human pricing effects may involve more sophisticated human-unique cognitive capacities, such as an understanding of market forces and signaling.

Introduction: The human hepatitis B virus causes acute and chronic hepatitis and is considered one of the most serious human health issues by the World Health Organization, causing thousands of deaths per year. There are similar viruses belonging to the Hepadnaviridae family that infect non-human primates and other mammals as well as some birds. The majority of non-human primate virus isolates were phylogenetically close to the human hepatitis B virus, but like the human genotypes, the origins of these viruses remain controversial. However, there is a possibility that human hepatitis B virus originated in primates. Knowing whether these viruses might be common to humans and primates is crucial in order to reduce the risk to humans., Objective: To review the existing knowledge about the evolutionary origins of viruses of the Hepadnaviridae family in primates., Methods: This review was done by reading several articles that provide information about the Hepadnaviridae virus family in non-human primates and humans and the possible origins and evolution of these viruses., Results: The evolutionary origin of viruses of the Hepadnaviridae family in primates has been dated back to several thousand years; however, recent analyses of genomic fossils of avihepadnaviruses integrated into the genomes of several avian species have suggested a much older origin of this genus., Conclusion: Some hypotheses about the evolutionary origins of human hepatitis B virus have been debated since the '90s. One theory suggested a New World origin because of the phylogenetic co-segregation between some New World human hepatitis B virus genotypes F and H and woolly monkey human hepatitis B virus in basal sister-relationship to the Old World non-human primates and human hepatitis B virus variants. Another theory suggests an Old World origin of human hepatitis B virus, and that it would have been spread following prehistoric human migrations over 100,000 years ago. A third theory suggests a co-speciation of human hepatitis B virus in non-human primate hosts because of the proximity between the phylogeny of Old and New World non-human primate and their human hepatitis B virus variants. The importance of further research, related to the subject in South American wild fauna, is paramount and highly relevant for understanding the origin of human hepatitis B virus., (Copyright © 2014 Elsevier Editora Ltda. All rights reserved.)