Hypotheses regarding the selective pressures driving the threefold increase in the size of the hominid brain since Homo habilis include climatic conditions, ecological demands, and social competition. We provide a multivariate analysis that enables the simultaneous assessment of variables representing each of these potential selective forces. Data were collated for latitude, prevalence of harmful parasites, mean annual temperature, and variation in annual temperature for the location of 175 hominid crania dating from 1.9 million to 10 thousand years ago. We also (...) included a proxy for population density and two indexes of paleoclimatic variability for the time at which each cranium was discovered. Results revealed independent contributions of population density, variation in paleoclimate, and temperature variation to the prediction of change in hominid cranial capacity (CC). Although the effects of paleoclimatic variability and temperature variation provide support for climatic hypotheses, the proxy for population density predicted more unique variance in CC than all other variables. The pattern suggests multiple pressures drove hominid brain evolution and that the core selective force was social competition. (shrink)

This paper presents the hypothesis that linguistic capacity evolved through the action of natural selection as an instrument which increased the efficiency of the cultural transmission system of early hominids. We suggest that during the early stages of hominization, hominid social learning, based on indirect social learning mechanisms and true imitation, came to constitute cumulative cultural transmission based on true imitation and the approval or disapproval of the learned behaviour of offspring. A key factor for this transformation was the (...) development of a conceptual capacity for categorizing learned behaviour in value terms - positive or negative, good or bad. We believe that some hominids developed this capacity for categorizing behaviour, and such an ability allowed them to approve or disapprove of their offsprings- learned behaviour. With such an ability, hominids were favoured, as they could transmit to their offspring all their behavioural experience about what can and cannot be done. This capacity triggered a cultural transmission system similar to the human one, though pre-linguistic. We suggest that the adaptive advantage provided by this new system of social learning generated a selection pressure in favour of the development of a linguistic capacity allowing children to better understand the new kind of evaluative information received from parents. (shrink)

Although many aspects of human cognition are likely to be passively affiliated with the primary impetus for hominid brain expansion during the Plio-Pleistocene, that expansion was most likely generated and maintained not by functions but by improved capacities of reproductive success, especially survivorship.

The overall objective is to explore the question of why our DNA is encoded to actualize an aesthetic experience that is autonomic and cognizant. It is proposed that the aesthetic experience is an adaptation selected by providing relief form the psychophysiological disorders that can arise from life’s burdens. It is further proposed that our aesthetic response to human form is an adaptation brought about by selecting alleles that generate an avoidance of mating with closely related species thus reducing the risk (...) of having less fit offspring, sterile offspring or no offspring. It is noted that with regard to human form apomorphic anatomical traits are attractive and plesiomorphic anatomical traits are unattractive. The term for this attitude has been coined cross species avoidance. The issue were addressed by interfacing philosophical aesthetics with evolutionary principles. (shrink)

This commentary criticizes Wilkins & Wakefield's thesis that the neurological precursors of language provide a cognitive Rubicon to linguistically divide human from nonhuman primates. A causal model of their theory is presented, followed by a discussion of the relationship between brain expansion and tool use, Broca's area and the parietaloccipital-temporal junction (POT).

Although features of the dentition figure prominently in discussions of early hominid phylogeny, remarkably little is known of the developmental basis of the variations in occlusal morphology and dental proportions that are observed among taxa. Recent experiments on tooth development in mice have identified some of the genes involved in dental patterning and the control of tooth specification. These findings provide valuable new insight into dental evolution and underscore the strong developmental links that exist among the teeth and the jaws (...) and cranium. The latter has important implications for cladistic studies that traditionally consider features of the skull independently from the dentition. BioEssays 23:481–493, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

the unprecedented measures regarding population mobility and dwelling that have been taken by states across the world have led the philosopher Giorgio Agamben to wonder whether the coronavirus pandemic represents the perfect opportunity for governments worldwide to take advantage of "collective panic" and instate the use of a state of exception as "a normal paradigm". Agamben's intervention in the global conversation about the impact of the pandemic has been met with outright criticism among some commentators for at least two reasons. (...) First, it seemed that he gave in too easily to the temptation of reading the reality of the quarantine zone containing potentially infected... (shrink)

In this response to essays by Barbara J. King, Gregory R. Peterson, Wesley J. Wildman, and Nancy R. Howell, I present arguments to counter some of the exciting and challenging questions from my colleagues. I take the opportunity to restate my argument for an interdisciplinary public theology, and by further developing the notion of transversality I argue for the specificity of the emerging theological dialogue with paleoanthropology and primatology. By arguing for a hermeneutics of the body, I respond to criticism (...) of my notion of human uniqueness and argue for strong evolutionary continuities, as well as significant discontinuities, between primates, humans, and other hominids. In addition, I answer critical questions about theological methodology and argue how the notion of human uniqueness, theologically restated as the image of God, is enriched by transversally appropriating scientific notions of species specificity and embodied personhood. (shrink)

Abstract. The concept of human uniqueness has long played a central role within key interpretations of the hominid fossil record and within numerous theological understandings of the imago Dei. More recently, the status of humans as evolutionarily unique has come under strong criticism owing to the discovery of certain nonhuman hominids who, as language and culture-bearing beings, lived as contemporaries with early anatomically modern humans. Nevertheless, many scholars, including those in the field of religion and science, continue to interpret (...) the remains of these other hominids in light of empirically ungrounded implicit assumptions about human uniqueness, which the author calls “anthropocentrism of the gaps.” This paper argues that “anthropocentrism of the gaps” is philosophically unwarranted and thus should not be assumed by scholars in religion and science when evaluating contemporary findings in paleoanthropology. (shrink)

Even as paleoanthropology becomes increasingly sophisticated in revealing both the broad contours and the details of the deep evolutionary history of Homo sapiens, it continues to be informed by lingering pre-evolutionary residues. Specifically, the goal of prior research was to demonstrate that the influence of the ancient Scala Naturae as an organizing principle significantly contributed to the scientific community’s delayed acceptance of Australopithecus as a plesiomorphic member of the Hominidae. The present study extends this research through a selective examination of (...) non-primary source material reporting on significant early hominid discoveries over the last century, beginning with Australopithecus africanus and ending with Ardipithecus ramidus. It is argued that these accessible sources reify to varying degrees the perception among the non-expert public that human beings are an inevitable culmination of the evolutionary process. This culturally transmitted schema of human exceptionalism continues to impact other life on Earth in profound ways, in some cases with calamitous results. (shrink)

Since the discovery of the Neandertal bones 1856, the extremely old, fragmentary fossil remains of hundreds of man-like bodies have been discovered in Europe, Asia, and Africa. Even the oldest ones - usually the most incomplete - look man-like and „un-apish", even to a layman, if compared with a modem apish and human correlate. Sometimes, in the vicinity of these remains, primitive stone tools or the evidence of their production have been found. At present, it seems absolutely certain — within (...) the limits of our present physical and biological knowledge - that at least four million years ago, in Africa, some creatures resembling modern man were living, and that at least two and half million years ago, in Africa, stone tools were produced. In contrast with the firm, scientifically-arguable belief that all modem human tribes - however different they are - belong to a single species, in paleoanthropology an equally firm scientific belief is maintained that the extinct man-like forms belong to several different, „presapient", „prehuman'', more ape-like species. (shrink)

Since the discovery of the Neandertal bones 1856, the extremely old, fragmentary fossil remains of hundreds of man-like bodies have been discovered in Europe, Asia, and Africa. Even the oldest ones - usually the most incomplete - look man-like and „un-apish", even to a layman, if compared with a modem apish and human correlate. Sometimes, in the vicinity of these remains, primitive stone tools or the evidence of their production have been found. At present, it seems absolutely certain — within (...) the limits of our present physical and biological knowledge - that at least four million years ago, in Africa, some creatures resembling modern man were living, and that at least two and half million years ago, in Africa, stone tools were produced. In contrast with the firm, scientifically-arguable belief that all modem human tribes - however different they are - belong to a single species, in paleoanthropology an equally firm scientific belief is maintained that the extinct man-like forms belong to several different, „presapient", „prehuman'', more ape-like species. (shrink)

The question of the origin of ‘natural’ human language has fascinated the scientific world for a very long time and seems to be generating a renewed level of interest. This paper will show that all elements converge to indicate a long and slow process of separation by which the hominids very progressively became distinguished from the other higher primates and more generally from other animal species. Biological and neurological developments created favourable structures for the future emergence of human languages. (...) These developments were further potentialized by the appearance of new forms of co-operation within human communities. Such anthropological, socio-cultural and ‘political’ elements were determinant in allowing the transition to the specifically human functions of language. If these elements are not taken into consideration, researchers are reduced to imaging the appearance of a mutation from which solely Homo sapiens would have benefited and from whichHomo neanderthalensis would have been excluded, as must equally be excluded any intermingling between the various varieties of hominids. (shrink)

Paleoanthropologists have long worked with the assumption that bipedism and brain enlargement evolved together in a cycle of cause and effect powered by the production of tools and instrumental manipulation. Rather, this paper argues, following the work of Paul Shepard, that discernments, or specific kinds of mentalities, arise from the relations that mammals and hominids form with their environments, other species and within their own social groupings.

One implication of Laland, Odling-Smee & Feldman's niche construction model concerns the significance of the role of behavioural or cultural traits in comparative analysis. In this commentary it is suggested that cladistic methods already recognise this importance, and that behavioural characters may play a key role in hominid speciation and the definition of species.

Cognition is readily seen to be connected to evolution through plots of the ratio of cranial capacity to body size of hominids which show two regions of sharply increasing ratios beginning at 2.5 and 0.5 million years ago – precisely the critical times inferred by the author from his study of tools. A similar correlation exists between current human brain growth spurts and the onsets of the Piagetian stages of reasoning development. The first goal of the author's target article (...) is stated to be “to make a case for the relevance of archeological contributions to studies of the evolution of cognition” (sect. 1, Introduction). His analysis focuses on spatial cognition. (shrink)

This article reconsiders the early hominid ‘‘lithic niche’’ by examining the social implications of stone artifact making. I reject the idea that making tools for use is an adequate explanation of the elaborate artifact forms of the Lower Palaeolithic, or a sufficient cause for long-term trends in hominid technology. I then advance an alternative mechanism founded on the claim that competency in making stone artifacts requires extended learning, and that excellence in artifact making is attained only by highly skilled individuals (...) who have been taught and practiced for extensive periods. Consequently both competency and expertise in knapping comes at a high learning cost for both the individual learner and the social group to which they belong. Those high intrinsic costs of learning created contexts in which groups selected cost-reducing forms of social learning and teaching, and in which specialization could develop. Artifacts and their manufacturing processes probably acquired functions as social signals—as honest signals of valuable capacities. The magnification of these signals, through competition between knappers and through inspiring later craftspeople, may account for a substantial amount of the accumulated elaboration visible in the archaeological record. Consequently lithic artifacts operated as material symbols from an early time in hominid evolution. (shrink)

Within the historical times, which roughly corresponds with the Holocene epoch, the whole of mankind is believed to be a single species. Homo sapiens. But the human genealogical tree is populated by a really astounding number of paleontological species and paleontological genera: Ardipithecus ramidus, Australopithecus anamensis, Australopithecus afarensis, Australopithecus africanus, Paranthropus robustus, Paranthropus boisei, Homo habilis, Homo georgicus. Homo erectus, Homo ergaster, Homo antecessor, Homo heidelbergensis, Homo neanderthalensis, Homo sapiens.. In fact there are many more but Foley, quite reasonably, states (...) that the evidence for their existence is, at present, insufficient. The existence of these multiple forms is beyond any doubt. The doubt, however arises concerning the human or „prehuman" status of them. Were they really true specific forms, half-way between the apes and Holocene man? Is it possible that they constitute a number of different ecotypes within the same natural species of Homo sapiens? (shrink)

Within the historical times, which roughly corresponds with the Holocene epoch, the whole of mankind is believed to be a single species. Homo sapiens. But the human genealogical tree is populated by a really astounding number of paleontological species and paleontological genera: Ardipithecus ramidus, Australopithecus anamensis, Australopithecus afarensis, Australopithecus africanus, Paranthropus robustus, Paranthropus boisei, Homo habilis, Homo georgicus. Homo erectus, Homo ergaster, Homo antecessor, Homo heidelbergensis, Homo neanderthalensis, Homo sapiens.. In fact there are many more but Foley, quite reasonably, states (...) that the evidence for their existence is, at present, insufficient. The existence of these multiple forms is beyond any doubt. The doubt, however arises concerning the human or „prehuman" status of them. Were they really true specific forms, half-way between the apes and Holocene man? Is it possible that they constitute a number of different ecotypes within the same natural species of Homo sapiens? (shrink)

A crucial design feature of language useful for determining when grammatical language evolved in the human lineage is our ability to combine meaningless units to form a new unit with meaning (combinatoriality) and to further combine these meaningful units into a larger unit with a novel meaning (compositionality). There is overlap between neural bases that underlie hierarchical cognitive functions required for compositionality in both linguistic and nonlinguistic contexts (e.g., tool use). Therefore, evidence of compositional tool use in the archaeological record (...) should signify, at the very least, the cognitive capacity for grammatical language by that point in time. We devise a novel system to evaluate the level of hierarchical nesting of tool components in single tool use activities. In the application of this system, we demonstrate that nonhuman primates, and by extension, the last common ancestor shared by Pan and Homo, are capable of basic combinatoriality; however, their technology does not approach the compositionality observable in modern human tool use. The prehistoric archaeological record supports a continuous evolution of combinatorial tool use into compositional tool use, with evidence for human-like levels of by 0.93 million years ago (Ma), or possibly as early as 1.7 Ma. While compositional language could have lagged behind compositional tool use, if language and technology coevolved according to the Technological Origin for Language hypothesis, which proposes a feedback system between the two, then evidence for hierarchical tool use structures implies a similar level of complexity in linguistic structures. (shrink)

To most people it seems obvious that there are major mental differences between ourselves and other species, but there is considerable debate over exactly how special our minds are, in what respects, and which were the critical evolutionary events that have shaped us. Some researchers claimlanguage as a solely human, even defining, attribute, while others claim that only humans are truly conscious. These questions have been explored mainly by archaeologists and anthropologists until recently, but this volume aims to show what (...) psychologists have to say on the evolution of mind. The book begins with a thorough overview of what is known of the non-primate mind and its evolution. Following this, an international range of experts discuss in temporal sequence the human mind at various stages of evolution, beginning with the pre-hominids of 20 million years ago and ending withcontemporary human behaviour. Accessible to students and researchers alike in psychology, anthropology, evolution, archaeology, and ethology, The Descent of Mind provides a range of provocative answers to the timeless question of what it means to be human. (shrink)

In contrast to many other models of human evolution the "balance of power" theory of Alexander has a clear answer to the question why a runaway selection process for unique social and moral capacities occurred in our ancestry only and not in other species: "ecological dominance" is hypothesized to have diminished the effects of "extrinsic" forces of natural selection such that within-species, intergroup competition increased (Alexander, 1989). Alexander seems to be wrong, however, in his claim that already the common HUCHIBO (...) (Humans, Chimps, Bonobo's)-ancestor has crossed the ecological dominance barrier. In this paper an adapted version of Alexander's model is presented and several different ways are proposed to make this adapted version testable. A preliminary survey of the available paleontological and paleoecological data suggests that there is some evidence of a less vulnerable position towards predators in early Homo and that there are clear signs related to a crossing of the ecological dominance barrier in Homo sapiens sapiens. (shrink)

'... this book to open up exciting new dimensions in the study of human evolution' Robin Dunbar School of Biological Sciences, Liverpool 'The book is billed as being of interest to a multi-disciplinary audience and meets its aim of befitting advanced students and researchers in evolutionary psychology, anthropology, evolution and palaeontology' QJEP Section BTo most people it seems obvious that there are major mental differences between ourselves and other species, but there is considerable debate over exactly how special our minds (...) are, in what respects, and which were the critical evolutionary events that have shaped us. Some researchers claim language as a solely human, even defining, attribute, while others claim that only humans are truly conscious. These questions have been explored mainly by archaeologists and anthropologists until recently, but this volume aims to show what psychologists have to say on the evolution of mind. The book begins with a thorough overview of what is known of the non-primate mind and its evolution. Following this, an international range of experts discuss in temporal sequence the human mind at various stages of evolution, beginning with the pre-hominids of 20 million years ago and ending with contemporary human behaviour. Accessible to students and researchers alike in psychology, anthropology, evolution, archaeology, and ethology, The Descent of Mind provides a range of provocative answers to the timeless question of what it means to be human. (shrink)

Researchers studying primate brain allometry often focus on departures from allometry more than the allometric relationships themselves because only the former reveal what brain regions and behavioral-cognitive abilities were the focus of selection. Allometric departures for the human brain provide insights into hominid brain evolution and cast doubt on the suggestion that the large human cerebral cortex is a.

The article analyzes the neural and functional grounding of language skills as well as their emergence in hominid evolution, hypothesizing stages leading from abilities known to exist in monkeys and apes and presumed to exist in our hominid ancestors right through to modern spoken and signed languages. The starting point is the observation that both premotor area F5 in monkeys and Broca's area in humans contain a “mirror system” active for both execution and observation of manual actions, and that F5 (...) and Broca's area are homologous brain regions. This grounded the mirror system hypothesis of Rizzolatti and Arbib (1998) which offers the mirror system for grasping as a key neural “missing link” between the abilities of our nonhuman ancestors of 20 million years ago and modern human language, with manual gestures rather than a system for vocal communication providing the initial seed for this evolutionary process. The present article, however, goes “beyond the mirror” to offer hypotheses on evolutionary changes within and outside the mirror systems which may have occurred to equip Homo sapiens with a language-ready brain. Crucial to the early stages of this progression is the mirror system for grasping and its extension to permit imitation. Imitation is seen as evolving via a so-called simple system such as that found in chimpanzees (which allows imitation of complex “object-oriented” sequences but only as the result of extensive practice) to a so-called complex system found in humans (which allows rapid imitation even of complex sequences, under appropriate conditions) which supports pantomime. This is hypothesized to have provided the substrate for the development of protosign, a combinatorially open repertoire of manual gestures, which then provides the scaffolding for the emergence of protospeech (which thus owes little to nonhuman vocalizations), with protosign and protospeech then developing in an expanding spiral. It is argued that these stages involve biological evolution of both brain and body. By contrast, it is argued that the progression from protosign and protospeech to languages with full-blown syntax and compositional semantics was a historical phenomenon in the development of Homo sapiens, involving few if any further biological changes. Key Words: gestures; hominids; language evolution; mirror system; neurolinguistics; primates; protolanguage; sign language; speech; vocalization. (shrink)

How does evolution grow bigger brains? It has been widely assumed that growth of individual structures and functional systems in response to niche-specific cognitive challenges is the most plausible mechanism for brain expansion in mammals. Comparison of multiple regressions on allometric data for 131 mammalian species, however, suggests that for 9 of 11 brain structures taxonomic and body size factors are less important than covariance of these major structures with each other. Which structure grows biggest is largely predicted by a (...) conserved order of neurogenesis that can be derived from the basic axial structure of the developing brain. This conserved order of neurogenesis predicts the relative scaling not only of gross brain regions like the isocortex or mesencephalon, but also the level of detail of individual thalamic nuclei. Special selection of particular areas for specific functions does occur, but it is a minor factor compared to the large-scale covariance of the whole brain. The idea that enlarged isocortex could be a a by-product of structural constraints later adapted for various behaviors, contrasts with approaches to selection of particular brain regions for cognitively advanced uses, as is commonly assumed in the case of hominid brain evolution. (shrink)

The strong predominance of right-handedness appears to be a uniquely human characteristic, whereas the left-cerebral dominance for vocalization occurs in many species, including frogs, birds, and mammals. Right-handedness may have arisen because of an association between manual gestures and vocalization in the evolution of language. I argue that language evolved from manual gestures, gradually incorporating vocal elements. The transition may be traced through changes in the function of Broca's area. Its homologue in monkeys has nothing to do with vocal control, (...) but contains the so-called “mirror neurons,” the code for both the production of manual reaching movements and the perception of the same movements performed by others. This system is bilateral in monkeys, but predominantly left-hemispheric in humans, and in humans is involved with vocalization as well as manual actions. There is evidence that Broca's area is enlarged on the left side in Homo habilis, suggesting that a link between gesture and vocalization may go back at least two million years, although other evidence suggests that speech may not have become fully autonomous until Homo sapiens appeared some 170,000 years ago, or perhaps even later. The removal of manual gesture as a necessary component of language may explain the rapid advance of technology, allowing late migrations of Homo sapiens from Africa to replace all other hominids in other parts of the world, including the Neanderthals in Europe and Homo erectus in Asia. Nevertheless, the long association of vocalization with manual gesture left us a legacy of right-handedness. Key Words: cerebral dominance; gestures; handedness; hominids; language evolution; primates; speech; vocalization. (shrink)

For a biological anthropologist interested in the prehistory of religion, J. Wentzel van Huyssteen's book is welcome and resonant. Van Huyssteen's central thesis is that humans' capacity for spirituality emerges from a transformation of cognition and emotions that takes place in the symbolic realm, within Homo sapiens and apart from biology. To his thesis I bring to bear three areas of response: the abundant cognitive and emotional capacities of living apes and extinct hominids; the role of symbolic ritual in (...) the evolutionary history of Homo sapiens; and the closely intertwined nature of biology and culture in the workings of evolutionary change. (shrink)

According to some psychological studies, women approaching ovulation feel the increased desire to have short-term sexual affairs with “sexy cads” while they are in long-term relations with “good dads.” I argue that this psychological property is a vestige of our evolutionary history. Early hominid females occasionally acquired good genes from top-ranking males while they were in long-term relations with low-ranking males. The Paleolithic living conditions indicate that women with the foregoing psychological trait were more likely to have viable children than (...) those without it. Sexy cads are the descendents of the top-ranking males, and good dads are the descendents of the low-ranking males. Sexy cads and good dads will continue to coexist in the future, developing better methods to detect cheaters and to escape detection. (shrink)

The first traces the production of numerous stone tools from the period of the Plio-Pleistocene represent a deep antiquity technical processes in the context of human evolution. Determining cognitive ability needed to convey the first hominids manufacture of stone tools is a challenge for the cognitive archaeology. Currently, thanks to archaeological discoveries and the development of cognitive science we can try to restore all the necessary treatments aimed at the production and use of stone tools along with a broad (...) understanding of their underlying cognitive processes. Analyses based on empirical data derived from Lokalalei – one of the oldest archaeological sites – indicate that the hominids comprehensive understanding of the principles of producing stone tools already at their very beginning. (shrink)

Hominid-like morphology in habiline cranial endocasts does not necessarily imply the presence of language capacity. The cortical zone in question is not associated exclusively with language in humans, and its emergence in habilines might indicate the evolution of other cognitive functions special to humans that were preconditions for the later evolution of language.

Since the nineteenth century, hominid palaeontology has offered critical information about prehistoric humans and evidence for human evolution. Human fossils discovered at a time when there was growing agreement that humans existed during the Ice Age became especially significant but also controversial. This paper argues that the techniques used to study human fossils from the 1850s to the 1870s and the way that these specimens were interpreted owed much to the anthropological examination of Stone, Bronze, and Iron Age skeletons retrieved (...) by archaeologists from prehistoric tombs throughout Europe. What emerged was the idea that a succession of distinct human races, which were identified using techniques such as craniometry, had occupied and migrated into Europe beginning in the Ice Age and continuing into the historic period. This marks a phase in the history of human palaeontology that gradually gave way to a science of palaeoanthropology that viewed hominid fossils more from the perspective of evolutionary theory and hominid phylogeny. (shrink)

The emergence of the hominids, more than five million years ago, marked the start of the human odyssey through space and time. This book deals with the last stage of this fascinating journey: the exploration of cyberspace and cybertime. Through the rapid global implementation of information and communication technologies, a new realm for human experience and imagination has been disclosed. Reversely, these postgeographical and posthistorical technologies have started to colonize our bodies and minds. Taking Homer's Odyssey and Kubrick's 2001: (...) A Space Odyssey as his starting point, the author investigates the 'informatization of the worldview', focusing on its implications for our culture-arts, religion, and science-and, ultimately, our form of life. Moving across a wide range of disciplines, varying from philosophical anthropology and palaeontology to information theory, and from astrophysics to literary, film and new media studies, the author discusses our 'cyberspace odyssey' from a reflective position beyond euphoria and nostalgia. His analysis is as profound as nuanced and deals with issues that will be high on the agenda for many decades to come. In 2003 a Dutch Edition of Cyberspace Odyssey received the Socrates Prize for the best philosophy book published in Dutch. (shrink)

Bipedalism in the earliest hominid specimens is always accompanied by the reduction of projecting canine teeth. Body size is smaller than chimpanzees or humans, but molar teeth are markedly larger. Use of a pointed stick for defensive purposes on the one hand, and digging for USOs on the other, may be why bipedalism was selected for. Passing such learned behavior to the next generation may have played a role in selecting for language.