Early stress predicts age at menarche and first birth,adult attachment,and expected lifespan

Life history theory suggests that in risky and uncertain environments the optimal reproductive strategy is to reproduce early in order to maximize the probability of leaving any descendants at all. The fact that early menarche facilitates early reproduction provides an adaptationist rationale for our first two hypotheses: that women who experience more risky and uncertain environments early in life would have (1) earlier menarche and (2) earlier first births than women who experience less stress at an early age. Attachment theory and research provide the rationale for our second two hypotheses: that the subjective early experience of risky and uncertain environments (insecurity) is (3) part of an evolved mechanism for entraining alternative reproductive strategies contingent on environmental risk and uncertainty and (4) reflected in expected lifespan. Evidence from our pilot study of 100 women attending antenatal clinics at a large metropolitan hospital is consistent with all four hypotheses: Women reporting more troubled family relations early in life had earlier menarche, earlier first birth, were more likely to identify with insecure adult attachment styles, and expected shorter lifespans. Multivariate analyses show that early stress directly affected age at menarche and first birth, affected adult attachment in interaction with expected lifespan, but had no effect on expected lifespan, where its original effect was taken over by interactions between age at menarche and adult attachment as well as age at first birth and adult attachment. We discuss our results in terms of the need to combine evolutionary and developmental perspectives and the relation between early stress in general and father absence in particular. This work was supported by The University of Melbourne Department of Obstetrics and Gynaecology. James S. Chisholm is Professor in the School of Anatomy and Human Biology at the University of Western Australia. He is an anthropologist whose interests lie in the fields of human behavioral biology, evolutionary ecology, life history theory, and parental investment theory, where he focuses on infant social-emotional development, the development of reproductive strategies, and the integration of evolutionary, developmental, and cultural psychology and public health. Julie A. Quinlivan is Associate Professor in Obstetrics and Gynaecology at the University of Melbourne and Head of the Maternity Care Program at the Royal Women’s Hospital, Melbourne. Her interests are teenage pregnancy, domestic violence, child abuse prevention, and high-risk pregnancy. Rodney W. Petersen is Senior Lecturer in Obstetrics and Gynaecology at the University of Melbourne and Senior Consultant in Obstetrics and Gynaecology at the Royal Women’s Hospital and Sunshine Hospital in Melbourne. His interests are in psychosocial aspects of women’s health and cancer. David A. Coall is a Ph.D. student in the School of Anatomy and Human Biology at the University of Western Australia. His main interest lies in the application of evolutionary theory within an epidemiological framework. He is currently working on the synthesis of life history theory, parental investment theory, and parent-offspring conflict theory in exploring factors that influence variation in human birth weight and placental weight.     

Animal Metaphors and Metaphorizing Animals: An Integrated Literary, Cognitive, and Evolutionary Analysis of Making and Partaking of Stories

Humans use metaphors to explore their relationship with nature. Our ability to make and understand metaphors appears to be an automatic cognitive process, one that likely evolved along with our ability to create and understand language. Because metaphors are processed automatically, without conscious appraisal, they can be used to rapidly communicate, or manipulate. Applying theories of evolutionary psychology and cognitive science to literary texts, we explored the role of animal metaphors in the making and partaking of stories in the context of a course in environmental studies. We investigated how humans are animals and yet use culture to shield themselves from this reality. We read and analyzed literature in which animal metaphors are central, such as Honoré de Balzac’s short story Passion in the Desert and Langdon Smith’s poem “Evolution.” Throughout the course, the overarching theme is that animal metaphors are powerful tools for framing our relationship with the environment and that they can be best understood in the context of humans as evolved animals.     

Norm enforcement among the Ju/’hoansi Bushmen

The concept of cooperative communities that enforce norm conformity through reward, as well as shaming, ridicule, and ostracism, has been central to anthropology since the work of Durkheim. Prevailing approaches from evolutionary theory explain the willingness to exert sanctions to enforce norms as self-interested behavior, while recent experimental studies suggest that altruistic rewarding and punishing—“strong reciprocity”—play an important role in promoting cooperation. This paper will use data from 308 conversations among the Ju/’hoansi (!Kung) Bushmen (a) to examine the dynamics of norm enforcement, (b) to evaluate the costs of punishment in a forager society and understand how they are reduced, and (c) to determine whether hypotheses that center on individual self-interest provide sufficient explanations for bearing the costs of norm enforcement, or whether there is evidence for strong reciprocity. Polly Wiessner is a professor of anthropology at the University of Utah. She has carried out fieldwork with the Ju/’hoansi of the Kalahari for the past 30 years on social networks, style in artifacts, economy, population, nutrition, and social change. She has also worked among the Enga of Papua New Guinea since 1985 on the oral history of exchange, ritual, and warfare.     

The expanded evolutionary synthesis—a response to Godfrey-Smith,Haig, and West-Eberhard

In responding to three reviews of Evolution in Four Dimensions (Jablonka and Lamb, 2005, MIT Press), we briefly consider the historical background to the present genecentred view of evolution, especially the way in which Weismann’s theories have influenced it, and discuss the origins of the notion of epigenetic inheritance. We reaffirm our belief that all types of hereditary information—genetic, epigenetic, behavioural and cultural—have contributed to evolutionary change, and outline recent evidence, mainly from epigenetic studies, that suggests that non-DNA heritable variations are not rare and can be quite stable. We describe ways in which such variations may have influenced evolution. The approach we take leads to broader definitions of terms such as ‘units of heredity’, ‘units of evolution’, and ‘units of selection’, and we maintain that ‘information’ can be a useful concept if it is defined in terms of its effects on the receiver. Although we agree that evolutionary theory is not undergoing a Kuhnian revolution, the incorporation of new data and ideas about hereditary variation, and about the role of development in generating it, is leading to a version of Darwinism that is very different from the gene-centred one that dominated evolutionary thinking in the second half of the twentieth century.     

The evolutionary ecology of attachment organization

Life history theory’s principle of allocation suggests that because immature organisms cannot expend reproductive effort, the major trade-off facing juveniles will be the one between survival, on one hand, and growth and development, on the other. As a consequence, infants and children might be expected to possess psychobiological mechanisms for optimizing this trade-off. The main argument of this paper is that the attachment process serves this function and that individual differences in attachment organization (secure, insecure, and possibly others) may represent facultative adaptations to conditions of risk and uncertainty that were probably recurrent in the environment of human evolutionary adaptedness. An early version of this paper was presented in the symposium “Childhood in Life-history Perspective: Developing Views” organized by Gilda Morelli and Paula Ivey for the Annual Meeting of the Society for Cross-Cultural Research in Santa Fe, New Mexico, February 16–20, 1994. James S. Chisholm recently joined the Department of Anatomy and Human Biology at the University of Western Australia. Previously he taught in the Department of Anthropology at the University of New Mexico and in the Division of Human Development at the University of California, Davis. He is a biosocial anthropologist whose research interests lie in the fields of human behavioral biology, evolutionary ecology, and life history theory, where he focuses on infant social-emotional development and the development of reproductive strategies in adolescence and young adulthood. In addition to numerous articles he is the author ofNavajo Infancy: An Ethological Study of Child Development (Aldine de Gruyter, 1983).     

Sober &; Wilson’s evolutionary arguments for psychological altruism: a reassessment

In their book Unto Others, Sober and Wilson argue that various evolutionary considerations (based on the logic of natural selection) lend support to the truth of psychological altruism. However, recently, Stephen Stich has raised a number of challenges to their reasoning: in particular, he claims that three out of the four evolutionary arguments they give are internally unconvincing, and that the one that is initially plausible fails to take into account recent findings from cognitive science and thus leaves open a number of egoistic responses. These challenges make it necessary to reassess the plausibility of Sober & Wilson’s evolutionary account—which is what I aim to do in this paper. In particular, I try to show that, as a matter of fact, Sober & Wilson’s case remains compelling, as some of Stich’s concerns rest on a confusion, and those that do not are not sufficiently strong to establish all the conclusions he is after. The upshot is that no reason has been given to abandon the view that evolutionary theory has advanced the debate surrounding psychological altruism.     

God’s punishment and public goods

Cooperation towards public goods relies on credible threats of punishment to deter cheats. However, punishing is costly, so it remains unclear who incurred the costs of enforcement in our evolutionary past. Theoretical work suggests that human cooperation may be promoted if people believe in supernatural punishment for moral transgressions. This theory is supported by new work in cognitive psychology and by anecdotal ethnographic evidence, but formal quantitative tests remain to be done. Using data from 186 societies around the globe, I test whether the likelihood of supernatural punishment—indexed by the importance of moralizing “high gods”—is associated with cooperation. Dominic Johnson is a fellow in the Princeton University Society of Fellows. He holds a D.Phil. in biology from Oxford University and a Ph.D. in political science from Geneva University. His research revolves around the evolutionary biology of human behavior and how this impacts on conflict, cooperation, politics, and religion. His recent book, Overconfidence and War: The Havoc and Glory of Positive Illusions, was published in 2004 by Harvard University Press.     

Patterns of characterization in folktales across geographic regions and levels of cultural complexity

Literary scholars are generally suspicious of the concept of universals: there are presently no candidates for literary universals that a high proportion of literary scholars would accept as valid. This paper reports results from a content analysis of patterns of characterization in folktales from 48 culture areas, aimed at identifying patterns of characterization that apply across regions of the world and levels of cultural complexity. The search for these patterns was guided by evolutionary theory and the findings are consistent with previous research on patterns of altruism, sex differences in mate preferences, sex differences in reproductive strategy, and differing emphases on male and female physical attractiveness. World literature, especially originally oral literature, represents a vast and neglected repository of information that researchers can use to more precisely map the contours of human nature. Jonathan Gottschall received his Ph.D. in English from Binghamton University and now teaches at St. Lawrence University in Canton, New York. His research focuses on integrating Darwinian approaches to human behavior and psychology with literary studies. The other authors are undergraduate students at St. Lawrence University.     

Rem sleep,early experience,and the development of reproductive strategies

We hypothesize that rapid eye movement or REM sleep evolved, in part, to mediate sexual/reproductive behaviors and strategies. Because development of sexual and mating strategies depends crucially on early attachment experiences, we further hypothesize that REM functions to mediate attachment processes early in life. Evidence for these hypotheses comes from (1) the correlation of REM variables with both attachment and sexual/reproductive variables; (2) attachment-related and sex-related hormonal release during REM; (3) selective activation during REM of brain sites implicated in attachment and sexual processes; (4) effects of maternal deprivation on REM; (5) effects of REM deprivation on sexual behaviors; and (6) the REM-associated sexual excitation. To explain why we find associations among REM sleep, attachment, and adult reproductive strategies, we rely on recent extensions of parent-offspring conflict theory. Using data from recent findings on genomic imprinting, Haig (2000) and others suggest that paternally expressed genes are selected to promote growth of the developing fetus/child at the expense of the mother, while maternally expressed genes counter these effects. Because developmental REM facilitates attachment-related outcomes in the child, developmental REM may be regulated by paternally expressed genes. In that case, REM may have evolved to support the “aims” of paternal genes at the expense of maternal genes. Patrick McNamara, Ph.D., is an assistant professor of neurology at Boston University School of Medicine and a member of the Department of Neurology at the Boston VA Medical Center. He specializes in study of catecholaminergic mechanisms of cognitive disorders in Parkinson’s and related disorders. He has a long-standing interest in anthropological and evolutionary approaches to medicine and to human cognition. His recent book Mind and Variability applied Darwinian models to problems of memory and identity. He is currently writing a book on the evolutionary psychology of sleep and dreams. Sanford Auerbach, M.D., is an associate professor of neurology and psychiatry at Boston University School of Medicine and medical director of the Neurophysiology Laboratories at the Boston Medical Center. He is a behavioral neurologist and a board-certified sleep specialist. He is also director of the Sleep Disorders Center at Boston Medical Center. He has been associated with the NIH-sponsored Sleep Heart Health Study and other sleep-related research. He has been a member of the executive committee of the Sleep Section of the American Academy of Neurology and a past chair of the Neurology section of the American Sleep Disorders Association. Jayme Dowdall is a medical student at Boston University School of Medicine who plans to specialize in molecular approaches to medical and sleep disorders.     

Biosemantics: An Evolutionary Theory of Thought

Evolutionary theory has an unexpected application in philosophy of mind, where it is used by the so-called biosemantic program—also called the teleosemantic program—to account for the representational capacities of neural states and processes in a way that conforms to an overarching scientific naturalism. Biosemantic theories account for the representational capacities of neural states and processes by appealing in particular to their evolutionary function, as that function is determined by a process of natural selection. As a result, biosemantic theories have distinct advantages over other theories of mental representation—e.g., Fodor’s causal theory. Foremost among the advantages of biosemantic theories is their ability to account for the possibility of mental misrepresentation.     

Kinship,sex, and fitness in a Caribbean community

Patterns of human kinship commonly involve preferential treatment of relatives based on lineal descent (lineages) rather than degree of genetic relatedness (kindreds), presenting a challenge for inclusive fitness theory. Here, we examine effects of lineage and kindred characteristics on reproductive success (RS) and number of grandchildren for 130 men and 124 women in a horticultural community on Dominica. Kindreds had little effect on fitness independently of lineage characteristics. Fitness increased with the number of lineal relatives residing in the community but decreased beyond an apparently optimal lineage size, suggesting resource enhancement and competition among kin. Female-biased patrilineage sex ratio was positively associated with men’s fitness, while male-biased matrilineage sex ratio was positively associated with women’s fitness. Number of brothers in the community was negatively associated with men’s, but not women’s, fitness. Parents and number of sisters had no effect on either male or female reproduction; however, women with younger sisters had higher RS, suggesting benefits of kin support for childcare. In sum, imposed norms for lineage social organization may enhance lineal ancestors’ inclusive fitness at a cost to individual inclusive fitness. Research was supported by grants from the National Science Foundation (BNS 8920569 and SBR 9205373); the University of Missouri Research Board to MVF; the Earthwatch Center for Field Research to MVF, Marsha B. Quinlan, and RJQ; and the B.S.U. Center for International Programs and Office of Academic Research and Sponsored Programs to RJQ. Marsha Quinlan and Napoleon Chagnon provided valuable advice on earlier drafts. Ed Hagen gave generous help with Descent software for kinship analysis. Many friends, teachers, and consultants in Bwa Mawego contributed generously to this study: the Durand clan—Juranie, Jonah, Elford, Induria, Margelia, Eugenia, Lillia, Elquimedo, Zexia, Delfine, Wilford, Nathalie, and Sarah; the Warringtons—Martina, Amatus, Onia, Belltina, Zabius, Sarah-Gene, and Heckery; the Laudats—Eddie, Benedict, and Dellie; the Laurents—Aron and Tito; the Lewises—Eddie, Melanie, Eulina, Spliffy, Ganjala, Julina, Jalina, and Marietta; Franklin Vigilante; Lawrence Prosper; Edmund Sanderson; Alex and Tita Alie; and especially Mistress Didi and Mr. McField Coipel. Rob Quinlan is Assistant Professor of Anthropology at Ball State University. His main interests include human evolutionary ecology, reproductive development, parental care, kinship, and medical anthropology. He has conducted fieldwork in Dominica since 1993. Mark Flinn is Associate Professor of Anthropology and Psychological Sciences at the University of Missouri-Columbia. His main interests include evolutionary theory, childhood stress, family relationships, and health. He has conducted fieldwork in Dominica every year since 1987.     

Chimera,spandrel, or adaptation

In every known human society, some kind—usually many kinds—of art is practiced, frequently with much vigor and pleasure, so that one could at least hypothesize that “artifying” or “artification” is a characteristic behavior of our species. Yet human ethologists and sociobiologists have been conspicuously unforthcoming about this observably widespread and valued practice, for a number of stated and unstated reasons. The present essay is a position paper that offers an overview and analysis of conceptual issues and problems inherent in viewing art and/or aesthetics as adaptive, and it presents a speculative account of a human behavior of art. Ellen Dissanayake is an independent scholar who has straddled the abyss between biology and art for more than twenty years. She is currently a Visiting Fellow at the Institute for Advanced Studies in the Humanities, University of Edinburgh.     

Art in global context: An evolutionary/functionalist perspective for the 21<Superscript>st</Superscript> century

Regarding the arts as something peopledo — as behaviors, rather than the residue or artifacts of behavior — makes possible a theoretical grounding about their nature and importance, an endeavor that current anthropology of art has largely abandoned. A reconsideration of the suspect and largely discarded terms “functionalism” and “evolutionism” is presented in light of current evolutionary thinking. It is suggested that a contemporary reformulation of these concepts, illustrated by the author's Darwinian or “adaptationist” perspective on art, supports aims and claims of current anthropology of art, and contributes new focus and direction to its endeavors.     

Chaotic dynamics of information processing: The “magic number seven plus-minus two” revisited

In a well-known collection of his essays in cognitive psychology Miller (The Psychology of Communication. Penguin, 1974) describes in detail a number of experiments aiming at a determination of the limits (if any) of the human brain in processing information. He concludes that the ‘channel capacity’ of human subjects does not exceed a few bits or that the number of categories of (one-dimensional) stimuli from which unambiguous judgment can be made are of the order of ‘seven plus or minus two’. This ‘magic number’ holds also, Miller found, for the number of random digits a person can correctly recall on a row and also the number of sentences that can be inserted inside a sentence in a natural language and still be read through without confusion. In this paper we propose a dynamical model of information processing by a self-organizing system which is based on the possible use of strange attractors as cognitive devices. It comes as an amusing surprise to find that such a model can, among other things, reproduce the ‘magic number seven plus-minus two’ and also its variance in a number of cases and provide a theoretical justification for them. This justification is based on the optimum length of a code which maximizes the dynamic storing capacity for the strings of digits constituting the set of external stimuli. This provides a mechanism for the fact that the ‘human channel’, which is so narrow and so noisy (of the order of just a few bits per second or a few bits per category) possesses the ability of squeezing or ‘compressing’ practically an unlimited number of bits per symbol—thereby giving rise to a phenomenal memory.     

Characters Are Key: The Effect of Synapomorphies on Cladogram Comprehension

Cladograms, phylogenetic trees that depict evolutionary relationships among a set of taxa, are one of the most powerful predictive tools in modern biology. They are usually depicted in one of two formats—tree or ladder. Previous research (Novick and Catley 2007) has found that college students have much greater difficulty understanding a cladogram’s hierarchical structure when it is depicted in the ladder format. Such understanding would seem to be a prerequisite for successful tree thinking. The present research examined the effect of a theoretically guided manipulation—adding a synapomorphy on each branch that supports two or more taxa—on students’ understanding of the hierarchical structure of ladder cladograms. Synapomorphies are characters shared by a group of taxa due to inheritance from a common ancestor. Thus, their depiction on a cladogram may facilitate the understanding of evolutionary relationships. Students’ comprehension was assessed in terms of success at translating relationships depicted in the ladder format to the tree format. The results indicated that adding synapomorphies provided powerful conceptual scaffolding that improved comprehension for students with both weaker and stronger backgrounds in biology. For stronger background students, the benefit of adding synapomorphies to the ladders was comparable to that of approximately two hours of instruction in phylogenetics that emphasized the ladder format.     

A Particular Synthesis: Aleksandr Promptov and Speciation in Birds

During the 1930s, Aleksandr Promptov—a student of the founder of Russian population genetics Sergei Chetverikov—developed an elaborate concept of speciation in birds. He conducted field investigations aimed at giving a naturalistic content to the theoretical formulations and laboratory models of evolutionary processes advanced within the framework of population genetics, placing particular emphasis on the evolutionary role of bird behavior. Yet, although highly synthetic in combining biogeographical, taxonomic, genetic, ecological, and behavioral studies, Promptov’s speciation concept was ignored by the architects of the 1930s and 1940s evolutionary synthesis, including Theodosius Dobzhnasky, Ernst Mayr, and Julian Huxley. In this article, I argue that the story of Promptov’s concept and its reception by other evolutionists challenges the traditional presentation of the synthesis as a singular, international process of the unification of biology, which led to the creation of a universal synthetic theory of evolution. It suggests that during the same time period, within largely the same theoretical framework, there were multiple, intrinsically local, attempts at creating synthetic evolutionary concepts. These concepts were often quite particular—in their taxonomic applicability, in their explanations of various evolutionary factors, and in the range of disciplines unified in the synthesis. Apparently, these concepts ran contrary to the universal aspirations of the synthesis architects, and as a result, they were disregarded, first by the architects and later by historians of the evolutionary synthesis.     

Evolutionary biology and feminism

Evolutionary biology and feminism share a variety of philosophical and practical concerns. I have tried to describe how a perspective from both evolutionary biology and feminism can accelerate the achievement of goals for both feminists and evolutionary biologists. In an early section of this paper I discuss the importance of variation to the disciplines of evolutionary biology and feminism. In the section entitled “Control of Female Reproduction” I demonstrate how insight provided by participation in life as woman and also as a feminist suggests testable hypotheses about the evolution of social behavior—hypotheses that are applicable to our investigations of the evolution of social behavior in nonhuman animals. In the section on “Deceit, Self-deception, and Patriarchal Reversals” I have overtly conceded that evolutionary biology, a scientific discipline, also represents a human cultural practice that, like other human cultural practices, may in parts and at times be characterized by deceit and self-deception. In the section on “Femininity” I have indicated how questions cast and answered and hypotheses tested from an evolutionary perspective can serve women and men struggling with sexist oppression. Patricia Adair Gowaty studies the evolution of social behavior, particularly mating systems and sex allocation, primarily in birds. She is most well-known for her long-term studies of eastern bluebirds, which began in 1977 and are on-going. She was an undergraduate at H. Sophie Newcomb College of Tulane University (1963–1967). In the late sixties and early seventies, while employed at the Bronx Zoo (New York Zoological Society), she belonged to a feminist “consciousness-raising” group. She started graduate school in 1974 at the University of Georgia and received her Ph.D. from Clemson University (1980). She had a postdoctoral position at the University of Oklahoma (1982–1983) and a visiting faculty position at Cornell University through the Visiting Professorships for Women NSF program (1983–1984) before returning to her bluebird study sites at Clemson in 1985. She has supported herself and her research efforts throughout her academic career on a series of awards and grants. She is currently (1990–1995) supported by a Research Scientist Development Award from The National Institute of Mental Health.     

A reexamination of Gilligan’s analysis of the female moral system

Gilligan’s (1982) refinement of Kohlberg’s theory on moral development operates on two theses: (1) females, more so than males, reach moral decisions based on the personalities of the relevant individuals; and (2) female behaviors stemming from moral decisions are based upon “care” and “responsibility for others.” This article accepts the first thesis but argues that the second is incorrect. That is, self-interest—i.e., aiding “blood” kin and/or carefully monitoring reciprocity—rather than “altruism” is argued to be the operant dynamic in forging distaff morality and resultant behavior. Six empirical examples are presented as contraindicative of Gilligan’s second thesis. Finally, it is suggested that selection for the psychological traits of independence and the mastery of subtle social chess yielded ancestral females who had more descendants—us—than did females with alternative profiles. Nancy S. Coney is a professor at Western Illinois University and is interested in both clinical and nonclinical aspects of women’s psychology. Wade C. Mackey is interested in biocultural anthropology and has authored two books on fathering:Fathering Behaviors (Plenum, 1995) andThe American Father (Plenum, 1996).     

Cognitive cooperation

Cooperation can evolve in the context of cognitive activities such as perception, attention, memory, and decision making, in addition to physical activities such as hunting, gathering, warfare, and childcare. The social insects are well known to cooperate on both physical and cognitive tasks, but the idea of cognitive cooperation in humans has not received widespread attention or systematic study. The traditional psychological literature often gives the impression that groups are dysfunctional cognitive units, while evolutionary psychologists have so far studied cognition primarily at the individual level. We present two experiments that demonstrate the superiority of thinking in groups, but only for tasks that are sufficiently challenging to exceed the capacity of individuals. One of the experiments is in a brain-storming format, where advantages of real groups over nominal groups have been notoriously difficult to demonstrate. Cognitive cooperation might often operate beneath conscious awareness and take place without the need for overt training, as evolutionary psychologists have stressed for individual-level cognitive adaptations. In general, cognitive cooperation should be a central subject in human evolutionary psychology, as it already is in the study of the social insects. David Sloan Wilson is an evolutionary biologist interested in a broad range of issues relevant to human behavior. He has published in psychology, anthropology, and philosophy journals in addition to his mainstream biological research. He is author of Darwin’s Cathedral: Evolution, Religion, and the Nature of Society (University of Chicago Press, 2002) and co-author with philosopher Elliott Sober of Unto Others: The Evolution and Psychology of Unselfish Behavior (Harvard University Press, 1998). John J. Timmel received his Ph.D. from Binghamton University in 2001. Ralph R. Miller is Distinguished Professor of Psychology at Binghamton University. His research interests include information processing in animals, with an emphasis on elementary, evolutionarily derived, fundamentals of learning and memory that might be expected to generalize across species, including humans.