Neanderthals

R E V I E W A R T I C L E

The ripples of modernity: How we can extend paleoanthropology with the extended evolutionary synthesis

Marc Kissel1 | AgustÍn Fuentes2

1Appalachian State University, Boone,

North Carolina

2Princeton University, Princeton, New Jersey

Correspondence

Marc Kissel, Appalachian State University,

Boone, NC.

Email: [email protected]

Funding information

Appalachian State University; University of

Notre Dame; Princeton University

Abstract

Contemporary understandings of paleoanthropological data illustrate that the search

for a line defining, or a specific point designating, “modern human” is problematic. Here we lend support to the argument for the need to look for patterns in the paleo-

anthropological record that indicate how multiple evolutionary processes intersected

to form the human niche, a concept critical to assessing the development and pro-

cesses involved in the emergence of a contemporary human phenotype. We suggest

that incorporating key elements of the Extended Evolutionary Synthesis (EES) into

our endeavors offers a better and more integrative toolkit for modeling and assessing

the evolution of the genus Homo. To illustrate our points, we highlight how aspects

of the genetic exchanges, morphology, and material culture of the later Pleistocene

complicate the concept of “modern” human behavior and suggest that multiple evo- lutionary patterns, processes, and pathways intersected to form the human niche.

K E Y W O R D S

extended evolutionary synthesis, hominin evolution, modern human origins, niche construction

1 | INTRODUCTION

How we approach the “typical” in our science is influenced by how we frame our research questions. For example, it has been recently dem-

onstrated that primatological fieldwork is focused on a few particular

taxa from a small number of field sites, biasing the broader perspective

of what primates do.1,2 Similarly, there is a bias in paleoanthropology

that privileges Western voices and the hypothetico-deductive model

of knowledge construction.3 As others have shown there is a bias in

where we dig, what we publish, and how we talk and think about

human evolution.4 However, recent work in biological anthropology

has focused attention on both regions and scholars whose contribu-

tions were often ignored, overlooked, or marginalized.2,5 And recently

discovered core evidence falling outside of standard expectations is

offering new insights and possibilities for paleoanthropology. For

example, Homo luzonensis,6 a 65,000 year old hominin from the Philip-

pines, offers critical novel information in part due to its discovery out-

side the “core” regions of human evolution. Similar work at Flores, Rising Star, and other sites have pushed the boundaries of not just

what is known about the variation in hominin morphology but with

how we conceptualize hominin species.

Patterns of bias set by preexisting expectations and assumptions

are robustly evident when we consider the quest for establishing

when humans became “modern” behaviorally and phenotypically. His- torically, paleoanthropological research has often focused on when

and where the suite of morphological and behavioral characteristics

that define contemporary humans evolved. This is not to say that all

paleoanthropologists have followed this “human revolution” model, and indeed many archeologists have pushed against this model for the

past few decades.7–17 As Shea noted in 2011 “The earliest H. sapiens were no less complete versions of us than we are incomplete versions

of whatever our species will look like 200,000 years from now. We

are merely different from one another.”8 Moreover, recent (and not so recent) discoveries have shown that material cultures and behav-

iors previously solely associated with modern humans seem to have

been present in some Neandertal populations.13,18–24 These data sug-

gest that previous hypothesis that separated the populations into

“modern” vs “archaic” no longer work.

Received: 9 November 2019 Revised: 5 September 2020 Accepted: 4 January 2021

DOI: 10.1002/evan.21883

84 © 2021 Wiley Periodicals LLC Evolutionary Anthropology. 2021;30:84–98.wileyonlinelibrary.com/journal/evan

Despite the recent and substantive push against a firm boundary in

defining “modern” humans or a specific time/place where they emerged in the Pleistocene, the concept of “modern” humans emerging due to a specific set of traits that resulted in higher fitness relative to other mem-

bers of the genus Homo persists across the broad field of human evolu-

tion. This perspective remains robust due to the majority of research

papers and overviews in this area relying heavily on evolutionary theory

developed during the New Synthesis25 and deploying the toolkit of

the Standard Evolutionary Theory (SET). Such an approach is not

always best suited to engaging the complexities of the human evolution-

ary record (or that of many other organisms).26–28 For this reason, exam-

inations of human evolution, particularly in the context of the later

FIGURE 1 One of the many hypothesized phylogenies of hominins. Image originally created by John Hawks

KISSEL AND FUENTES 85

Pleistocene, sometimes overlook or underplay the interactive and func-

tional roles of gene flow, genetic drift, hybridization, niche construction

and symbolic inheritance (But see10,29–31 for exceptions, as well as

the work of Mary Stiner32 and Terry Deacon33). While this pattern is

changing34 there remains a significant lack of incorporating key ele-

ments of the Extended Evolutionary Synthesis (EES) toolkit into studies

of human origins. In this paper we discuss how the EES may be useful in

paleoanthropological approaches and why its inclusion can help us to

more effectively conceptualize the processes by which earlier members

of the genus Homo became human. To illustrate our points we highlight

aspects of aDNA studies, morphology, and the concept of “modern” human behavior to demonstrate how the concept of niche construction

can facilitate a better, more integrated paleoanthropology.35 In sum, we

argue that we need to look for the patterns in the paleoanthropological

record that illustrate how multiple evolutionary processes intersected to

create the modern human phenotype.

2 | WHAT IS A HUMAN?

There is considerable disagreement over how many species are repre-

sented in our lineage and how they relate to one another.36–38 We

have no consistent species definition for past hominins, especially for

members of genus Homo, nor solid agreement among researchers on

how to develop one.9,38,39 There is, however, near unanimous agree-

ment that by about 1 million years ago, all populations of hominins on

the planet belonged to the genus Homo, with all other hominin lineages

having gone extinct. There is also widespread agreement that there is

substantial morphological variation in populations of the genus Homo

over the last million years, with many different morphotypes living in

temporal and occasionally geographical overlap. Whether these differ-

ences reflect species level distinctions is up for debate (Figure 1).

For the last half century paleoanthropologists and archeologists

relied on two major developments as having “identified” the emer- gence of contemporary humans: behavioral modernity and anatomical

modernity.7,8,40–42 Anatomical modernity (fossils that are morphologi-

cally contiguous with contemporary humans) was initially used as a

core marker of “being human.” But the dates of such fossils are highly variable, going from �100,000 years ago, to 180,000 years ago, to �300,000 years ago, depending on which fossils and which morpho- logical markers one uses. The concept of behavioral modernity relies

on a “human revolution”7,8,43 in which significant cognitive changes created a disjuncture between Homo sapiens (true humans) and our

closest hominin relatives (other members of the genus Homo). Until

recently, this shift was identified by the appearance of “symbolic” artifacts in the archeological record. If an ancient population made

symbolic items, it was cognitively human. The timing of this event

has been variously pegged to the appearance of cave art and carved

figures (�65–40 kya), to specific types of stone tool technologies (�75 kya), and more recently to the use of ochre for engravings and pigments (�180–80 kya).

As the above dates show, it is difficult to pinpoint when in the

Pleistocene some populations of Homo became contemporary humans

(“modern”) relative to others. This may be due to the problems inher- ent in delineating specific behaviors or anatomical traits that separate

“modern” from “archaic” forms. Determining the First Appearance Date of a behavior, especially artifacts that are ephemeral and equivo-

cal (and the processes that created them equifinal), is often based on

an SET perspective that sees the environment producing changes that

necessitate a new behavior. But calculating when and how the fitness

of engraving on ochre, for example, became a significant selective

pressure on Homo is difficult, and may not even be the right question.

As Wilkins recently demonstrated in regard to Named Stone Tool

Industries (NASTIEs), appropriately designed research agendas that

are divorced from NASTIEs as the significant units of analysis and

more focused on the processes and patterns of the production and

use of the various tools and component items themselves may better

address many of the questions relevant to understanding the creators

and users of said tools.44

Each passing year sees an expansion of the dataset for Pleisto-

cene Homo and heralds yet another change to the criteria for dividing

“true” humans and other human-like members of genus Homo. The package of morphological traits we once labeled “anatomically modern” shows up in varying forms, in varying places, and in different populations of Homo across Africa and Eurasia over the last

400,000–300,000 years.7 Almost every type of material evidence, of

“symbol” or other indicators of substantive and repetitive meaning- making,45 that were considered indicators of uniquely modern human

cognition also show up associated with populations that do not have

contemporary human morphology.42 It has become increasingly clear

that what makes us human is not the emergence of a chin, more verti-

cal frontal bones or a high rounded cranium, nor is it the creation of

symbolic artifacts, language, conscious thought, or anything of that

nature. Rather, what makes us human is the shared evolutionary line-

age of Homo sapiens.

Another problem is the confusion caused by referring to samples

as “modern.” If a sample can be fully modern does that mean another population is only partially modern? In other words, is modernity

something that has levels of variation and suites of behavior? Once a

“modern” form evolves what can we call the non-modern forms that flourished alongside it? Finally, what does the presence of not-fully-

modern samples tell us about the evolutionary processes acting on the

human niche? It would seem to support an accretion of traits associ-

ated with the mixing of different samples, including unknown ghost

samples.46,47 In other words, hybridization.29,48 But it leads to more

questions: Can one sample can really be more “modern” than another and how would we measure that? Are some populations less modern

because they have many, but not all, of the specific traits that we con-

sider to be the shared derived characteristics of Homo sapiens sapiens

(contemporary humans)? The very concept of “modern” is problematic both theoretically and practically when applied to most populations of

Homo that lived in the terminal Pleistocene.

We also need to be aware of how language affects this discourse.

Just as the terms “New World” and “Old World” are problematic (new to who? And old to who?), “modern” and “non-modern” can set the stage for “grades” of humanity approaches used to justify colonial

86 KISSEL AND FUENTES

and racist assertions and actions. The very concept of modern is prob-

lematic from an evolutionary perspective.

Simply put, delineating the time and place that we became human

is rooted in a narrative of human evolution that tracks the “hero's journey.”49 Post-Holocene humans are often the comparison point of other populations, such as the Neandertals. Becoming human was and

is an evolutionary process; there is no clear line in the last half million

years where we can state with absolute certainty “this group of fossils are our one and only direct ancestors.” The evidence suggests, on the contrary, that many populations in the genus Homo contributed to

contemporary humanity.10,50 As our knowledge of the human fossil

and archeological records expands, and as our ability to develop more

robust genetic and evolutionary models increases (as we will note

especially via incorporation of the EES), we can demonstrate that the

last half million years is a time of major transitions in genus Homo's

biology and behavior, not simply the emergence of the “true” human. Rather than seeing changes as radical shifts and boundary cross-

ing events in material cultures that indicate new and distinctive cogni-

tive capacities, and fitness values, and thus a new species, we can see

them as ongoing processes in the human niche. Contemporary Homo

sapiens' presence was not due to a set of specific morphological or

material adaptations but rather a suite of changes in how they per-

ceived and interacted with the world and each other: a change in the

human niche.51,52 Across the Pleistocene the genus Homo underwent

significant changes in physiology, ecology and behavior developing a

distinctively human niche.51–56 Over the last 500,000 years the com-

plexity (materially, behaviorally and culturally) of this niche ratcheted

up in increasingly dynamic ways affording the patterns we see in con-

temporary humanity.

Many of our models are predicated on looking for speciation

events. As demonstrated by recent advances in aDNA,47,57–62 archaic

admixture and introgression, mixed with purifying selection that can

create the appearance of “archaic deserts,”59 has had a profound and salient impact on the modern human genome. If we stopped using

“modern” as a sample types/identifier what would happen? We may find ourselves talking about populations changing. Omo, Jebel Irhoud,

Apdima, Florisbad, and Kabwe are not modern in the contemporary

sense, but they were ‘modern’ for their time and the distinctions between them and us may predominantly be their temporal position

and the fact that they lack some derived traits we have, and maybe

we lack traits/behaviors they had. We need to be clear that as humans

evolve and our niche changes, so do we. In other words, the human

niche (both behaviorally and anatomically) is dynamic and thus we

need a dynamic evolutionary approach to best understand and model

it in the past.

2.1 | The EES is necessary to better understand human evolution

In most approaches rooted in the SET the actions of natural selection

and the resultant functional changes (adaptations) are the key to the

origins and mechanisms of evolutionarily relevant traits, behaviors

and structures. It is quite common in explanations of human evolu-

tionary processes and patterns to invoke specific selection events,

such as extreme climatological pressures, sexual selection and specific

fitness enhancing scenarios, or direct competition between hominin

species in setting up adaptive trajectories (seen as the most valid

explanations) for patterned changes in the fossil and archeological

record of Pleistocene Homo.

Be they explanations of morphological, behavioral or ecological

shifts, the primary “go to” explanatory scenario tends to be selection acting on a specific trait or set of traits as the key to understanding

the shift in the features of interest.63 For example, this plays out in

broad scale assertions for violence and aggression with traditional

camps arguing for specific selection focused scenarios based on intra-

group control of violence and intergroup competition,64,65 in the

explanations for the disappearance of certain Homo morphotypes and

archeological assemblages,66 in the explanations for variation in body

size dimorphism via targeted sexual selection and monogamy,67,68 in

fitness signaling explanations for the Acheulean toolkit,69 and even

for the emergence of the use and control of fire.70

However, there is also a substantial body of work that demon-

strates that the actual fossil and archeological record reflect more

complex and more diverse assemblages, processes and patterns than

are inferred and asserted by the trait-focused, selection-driven sce-

narios above.53,71–74 Contemporary evolutionary theory, termed the

Extended Evolutionary Synthesis (EES),75 does not limit evolutionary

inquiry to a focus on natural selection as the sole architect of function.

Nor does it focus only on one mode or level of evolution (biological

and cultural, genic, individual and group). Rather, it includes a plurality

of evolutionary processes, from selection to niche construction to

developmental plasticity, and others, as potentially mutually inter-

acting in evolutionarily relevant and reciprocally causal or mutually

influential modes, and thus relevant in the analyses of evolutionary

patterns and trajectories.26,76 Such a dynamic is open to causally het-

erogeneous processes and thus melds more effectively than selection

only (or mostly) explanations with the complexities and dynamics cur-

rently evident in the fossil and archeological records of Homo; espe-

cially in the context of the emergence of contemporary human

processes and patterns over the terminal Pleistocene.

For example, historically, descriptions of human evolution, in par-

ticular, often ignore or downplay the possibility that significant and

substantive phenotypic variation and change can be primarily affected

by movement and mating (gene flow) and genetic drift as major evolu-

tionary processes. But much current work highlights these processes

as primary forces in many cases.31,77–81 The shift from a search

for selection on “genes” to a recognition of genomic/epigenomic/ developmental dynamics as potentially central explanatory pathways

challenges the primacy of DNA sequence variation (“genes” in the SET) as our target and opens our toolkit to more diverse explanatory

inquiry options. In the EES context, as in the SET, genetic mutation

introduces genetic variation. However, in the EES one explicitly, and

causally, recognizes that these new sequences interact not only with

one another, but with the inner workings of cells and other systems

(epigenetic systems) that affect how DNA functions. Also in the EES

KISSEL AND FUENTES 87

there is explicit recognition that such interactions are drawn into, and

potentially shaped by, the range of developmental processes.82,83

Suites of interactions, from DNA to epigenetics to the developmental

processes of bodily systems, produce biological variation in organisms

that may be passed from generation to generation. Genes are never

alone or static “combatants,” nor are they necessarily the ultimate arbitrator of whether or not evolution is happening.

It is well understood that natural selection shapes the details and

patterns of genetic and epigenetic variation from generation to gener-

ation in response to specific constraints and pressures in the environ-

ment. But, it is equally understood that the patterns and processes of

genomic and epigenomic and developmental interfaces can also pro-

duce the patterns observed in the fossil, and archeological, record

without having to default to specific and focused selection models as

the ultimate explanandum.27,84–86

Gene flow and genetic drift have recently been demonstrated to

be extremely important in later Pleistocene genus Homo evolution

and thus should be central aspects of any explanatory frameworks

applied to our lineages' evolution. Selection, gene flow and genetic

drift are all central features of evolutionary processes, but even they

are not the only, or always the most relevant, processes available for

our toolkit. Genetic variation is the basal material that core evolution-

ary processes work on. However, it is clear from the Pleistocene fossil

and archeological record that much more than patterns of genetic

variation have played substantive roles in the trajectories and intrica-

cies of the evolutionary histories of the genus Homo.35,36,53,54,80

Engaging the EES enables a more comprehensive, and thus effective,

evolutionary toolkit for the study of human evolution, one that explic-

itly is open to the possibilities that other than genic evolution, and

more than targeted selection, may be playing central, and causal or

facilitatory, roles in shaping the details and the trajectories of evolu-

tionary patterns.

Specifically, the processes of niche construction, the patterns

and capacities of phenotypic plasticity, and the fact that multiple

modes of inheritance can be evolutionarily relevant creates a dynamic

wherein traditional processes of the SET (genetic mutation, genetic

inheritance, gene flow, genetic drift, natural selection) interface with

additional modalities (developmental processes, niche construction,

developmental bias and plasticity, phenotypic accommodation, epige-

netic, ecological, behavioral, and cultural inheritances) presenting

a multi-process model that is well suited to the complexities evident

in the Homo fossil and archeological record. The basic parameters of

the EES are well outlined by Laland and colleagues,75 in their Figure 2,

and the outcomes, definitions and expectations well reviewed in

tables 1–3 of that publication (see also26,27,87). We offer a very brief

summary of the key EES factors specifically of interest to human evo-

lutionary studies here in order to illustrate how they provide a robust

template for assessing and understanding human evolution.

FIGURE 2 Some of the middle Pleistocene crania from Africa in oblique (3/4) view. Starting in the upper left corner: Eliye Springs (KNM-ES 11693); Jebel Irhoud 1; Jebel Irhoud 2; Kabwe; Florisbad; LES1; DH3; DH1. Image credit John Hawks

88 KISSEL AND FUENTES

Niche construction is the building, modifying, and destroying of

niches via the mutual interactions between organisms and their imme-

diate environments, which can sometimes change both. As Laland et al.

state; the EES “views evolutionary causation as reciprocal and hence that organisms co-evolve with their environments. Environments modi-

fied by organisms viewed as qualitatively different from independent

environmental states. Niche construction treated as a process that

directs evolution by non-random modification of selective environ-

ments. Niche construction may result from acquired characters, by-

products and the accumulated outputs of multiple species.”75 The effects of niche construction can shape the patterns and intensity of

natural selection and other evolutionary processes75 and create ecolog-

ical inheritances in the form of altered ecologies passed down across

generations.88,89 Both of these outcomes can change the evolutionary

pressures on subsequent generations. The Pleistocene record of the

genus Homo is rife with examples of these types of process and out-

comes as central to the lives of the genus Homo. See Box 1.

Social environments are as susceptible, if not more susceptible, to

niche construction than material environments. “Through niche con- struction organisms not only influence the nature of their world, but

also in part determine the selection pressures to which they and their

descendants are exposed, and they do so in a non-random manner.”103

For contemporary humans the human niche is the ecology involving

the spatial, social, and perceptual landscapes of humans, our social

partners, perceptual contexts, and ecologies of individuals and commu-

nities, including the many other species sympatric with humans. The

human niche is the context for the lived experience of humans and

their communities, where they share kinship and social and ecological

histories, as well as shared knowledge, social and structural security,

and development across the lifespan.104 Thus, understanding the

developmental details and processual dynamics of this contemporary

human niche is a key in understanding the transition to contemporary

Homo sapiens from earlier Homo populations across the Pleistocene.

Plasticity and flexibility (or lack thereof) across developmental pro-

cesses manifests in the lived experiences of organisms and shapes the

patterns, the structures and the production of evolutionarily relevant

outcomes.82 Given the extensive patterns of morphological9,36–38 and

behavioral variation40,41 across the Pleistocene for members of the

genus Homo, plasticity and flexibility in behavior, bodies, and develop-

ment may also be of significant evolutionary relevance to our assess-

ments and models.53,94,104 For example, the substantial extension of

the juvenile period and the post-partum neurobiological growth and

development facilitates a wide range of behavioral, cognitive, and mor-

phological variation and dynamism that emerges from the potential

and structural plasticity in such patterns of growth.105 Regardless of

whether this variability stems from direct selection, genetic drift or

gene flow, the specific affordances of local ecologies (social and

material), and/or a wide latitude of developmental constraints on “suc- cessful” form (e.g., variation in the Dmanisi hominins or the range of contemporary middle Pleistocene Homo morphotypes), its existence

may act, in and of itself, as a processes enabling and/or constraining

particular evolutionary changes and trajectories.

Finally, recent recognition of the fact that there are multiple

modes for the inheritance of evolutionarily relevant variation from

generation to generation (genetic, epigenetic, behavioral and cultural/

symbolic),87 mandates that attention must be paid in our investiga-

tions of Homo evolution specifically to the transmission of variation

across genetic, epigenetic, and behavioral avenues.35,75 This is under-

way with the augmented study of aDNA and paleoproteins,50,106,107

with the analyses and inferences of life history shifts and develop-

mental processes via fossil remains108 and via increased attention to

specific modulations and modification of material and ecological indi-

cators of behavior in the archeological record.97 Because humans can

also create and inherit symbols, perceptions and beliefs, which can be

evolutionarily relevant109–111 such processes should be included in

models of human evolution. The extant data suggest that, especially in

the last 400,000–300,00 years, such modes of transmission of poten-

tially evolutionarily relevant information are ubiquitous, contiguous,

and yet variable in the specifics of the content and modalities, across

the entire range of Homo populations.

The view of evolution we review here includes a plurality of

casual processes and the possibilities of reciprocal causation among

them, and does not require trait or trait-complex adaptive fitness

modeled via natural selection as ultimate arbiter of the validity and

power of a casual explanation (but does not exclude such explanations

as options). In sum, evolution occurs via a complex of dynamic interac-

tions by which populations of organisms both shape and are shaped

by many aspects of their environment, behavior, genomes, morphol-

ogies and histories. The interfaces between these dynamics produce

niches that are co-constructed, inherited and altered across space

and time.

The Homo fossil and archeological records reveal increasing brain

sizes and changing neurobiological capabilities, and myriad changes to

morphology and behavior as reflected by material remains across evo-

lutionary time. The development of the human niche is the process by

which the bodies, minds, and lives of the members of the genus Homo

have changed.51,55 It is the ongoing dynamics in the human niche that

sets the stage for the context in which we find, and need to explain,

the patterns and processes of the evolution of the genus Homo, and

the emergence of the specific patterns characterizing contemporary

Homo sapiens. It should be clear from this brief overview that the EES

offers a wider range of evolutionary processes with which to engage

the data from the fossil and archeological record of Homo across the

Pleistocene. Below we briefly illustrate three particular areas where

engagement with the EES might add to our capacities to develop bet-

ter models and augment the depth and effectives of our understand-

ings of how we become human.

2.2 | Becoming human: Patterns, process, and complexities in three examples

2.2.1 | What does it mean to be genetically modern?

For the past three decades there has been a consistent set of two

main predictions as to what the genetics of the genus Homo over

the terminal Pleistocene would show if we had a complete record.

KISSEL AND FUENTES 89

Box 1 Examples of niche construction in the Pleistocene

Following the definition of niche construction as the building, modifying, and destroying of niches via the mutual interactions between

organisms and their immediate environments, we can see that hominins have been engaged in significant modification of their niches at

a level that seemingly surpasses, or is at least distinctive from, nonhuman primates. Examples include: early stone tool development and

the modifications to diet and behavior made possible with those tools,90 the emergence of intensive cooperative investment in caretak-

ing and food sharing,91,92 the successful geographic expansion of the genus Homo,93 changes in life history strategies that altered social

and ecological interfaces,94 the development of more and more complex tool types and greater diversity of materials used, the develop-

ment of increasingly diverse extra-somatic modes of modifying material items and local ecologies,95,96 the emergence of long-distance

transport and possibly trade,97 and the innovation, creation, and sharing of meaning-laden materials. These are all documented in the

Pleistocene Homo record.

All of these aspects (and more, see below) in the genus Homo can be seen as actions/outcomes that result in the non-random modi-

fication of selective environments creating ecological inheritances in the form of altered ecologies passed down across generations. This

is niche construction, and it is increasingly dense and substantial in impact in later Pleistocene Homo compared to nearly all other organ-

isms, and likely has structural and shaping effects on phenotypes, genotypes, developmental processes and thus evolutionary

systems.36,54,88,98,99

A particularly salient example comes from the use and control of fire. Natural fires were part of the early hominin niche, and for

most modern humans it is both required for cooking and embedded in the fabric of social interactions.95,100 Chazan95 argues for a

three-stage development of the use of fire by humans, from opportunistic interaction, enhanced and sophisticated maintenance of fire

at base camps by 200,000 years ago, and the enclosure of fire with hearths and the habitual use of techniques to create fire. As he

argues “The concept of a long prehistory of fire moves away from viewing technology as an endowment made possible by favorable genetic mutations toward a more complex conception that looks at the interplay between genetics and culture in driving hominin

evolutions.” While much debate still exists as to the timing of when hominins could produce and control fire it seems clear that its effects were

multitudinous, and niche altering. Fire allows Homo to protect themselves from predators, keep warm, and obtain more energy from

foods (Wrangham's cooking hypothesis101 suggests that fire allows for an increase in the amount of energy that can be acquired from

food and reduces the need for dietary adaptations). Moreover, social interactions and information sharing around the fire may have

changed the social landscape and thus enacted a major change in the human niche. Wiessner102 notes that the talk at night over firelight

for the Ju/'hoan is focused on dancing, singing, religious activities, and telling stories, rather than discussions about subsistence or idle

gossip. These campfire stories describe the workings of society, linking individuals from distinct bands into larger “imagined communi- ties.” She argues that humans were using firelight for intimate, economically unproductive conversations since perhaps 300,000–200,000 years ago. These nighttime conversations, made possible through altering the human niche in a novel way that

allowed more time to interact socially during a previously unproductive time when other tasks may not be possible, could be critical in

the social and cooperative, and technological, abilities of humans. Apprenticeship and other forms of learning would have been

ratcheted up, as peers shared stories and discussed people far away, linking these more distant people to the local band members in a

manner not done before.

A non-genetic behavioral and ecological change (fire use) altered the social and material environment in which humans existed.

They then passed this novel environment down (symbolic, behavioral, and ecological inheritance), affecting the way evolutionary pro-

cesses interacted with the human phenotype. “[S]hifts in technology might have altered the selective advantage of traits already existing in populations, leading over time to changes in allele frequencies and ultimately to speciation.”95 It also produced non-genetic changes in the human phenotype. Humans were co-evolving with the new landscape they created and not just in terms of changes in jaw struc-

ture and teeth (though these are as important in both the EES and the SET)

As we note in the text, social environments are as susceptible to niche construction.

The recognition that MSA hominins at Olorgesailie procured obsidian from �50 km away reflects a level of innovation in behavior. The creation and maintenance of these likely trade networks allow not just the mitigation of risk but also increases social connections.

These changing social networks and patterns of material exchange are, like fire use, a change in the human niche. It produces changes in

the way humans interact with their social and material environments in distinctive manners. For instance, the increase in the use of

“symbolically” mediated artifacts such as ochre, shell beads, engraved artifacts, and so forth. between 300–200 ka, and possibly earlier, may correlate with these new ways of seeing how to interact with people that might not be directly known to the people they are trad-

ing with. But it also opens up ideas about increasing the circle of who you see as a member of your group, building community, and

changing how you interact with strangers.

90 KISSEL AND FUENTES

The first sees a population (or a few connected populations) in Africa

that coalesced and spread out of Africa in the last 300,000–

50,000 years and is the basis for the majority of genetic variation in

contemporary Homo sapiens. The second sees all contemporary Homo

sapiens sharing an African origin, but suggests different geographic

regions have developed genetic trajectories that helped shape con-

temporary human patterns.

Recent work in aDNA, archeology and fossil discoveries reveal

that second model is incorrect in the sense of Pleistocene Homo having

genomic “regional continuity” with contemporary populations and that first model is overly simplistic.3,50 Twenty years ago, Alan Templeton

offered an alternative to these two positions, and since then others

have also emerged. Templeton proposed the “lattice” model,112 where he pointed out that patterned exchange of genetic materials appears

to have been sporadically present across populations of the genus

Homo throughout the Pleistocene, rendering both models insufficient

and misleading. However, even Templeton's lattice model appears to

underrepresent the dynamics of our evolutionary past.48,113

A broad consensus is developing (but not quite there yet) that

in the time period between 500,000 and 100,000 years ago large

African meta-populations of the genus Homo, with some connectivity

to populations outside of Africa, form the genomic basis for contempo-

rary Homo sapiens. However, this must also be connected to the

increasing evidence of substantive genetic exchange between a myriad

of populations of the genus Homo, not connected directly to contem-

porary Homo sapiens, and those African meta-populations or their

descendants across the terminal portions of the Pleistocene.48 There is

also strong evidence for complex histories of structuring across all of

these populations and little clear archeological or other evidence for

any pattern of more “effective,” “advanced” or “better fit” technolo- gies, behaviors or other population specific characteristics that would

indicate any form of out-competition or direct replacement models.

To put it succinctly, the genetic data we have available make it

unclear if we can accurately label different Homo populations across

the latter Pleistocene as different species, as genetically “better” or “worse” adapted, as our “direct” ancestors, or to exclude them all together from genomic connectivity to contemporary humanity

(although the Homo floresiensis and Homo naledi may be good candi-

dates for such classifications). This suggests that searching for a suite

of genetic patterns that were targeted by selection and resulted in a

higher fitness value population (or populations) relative to other Homo

populations emerging as the ancestral pool for contemporary Homo

sapiens is both a likely oversimplification of evolutionary processes

and not reflective of the patterns of genomic processes across

much of the later Pleistocene Homo. There is no clear genetic Rubicon

of “modernity” for Pleistocene Homo populations. If this is the case across all measures of terminal Pleistocene Homo history (as it seems

to be, see morphology and behavior sections below) we cannot rely

on straight-forward selection models of inter-specific or inter-group

competition to explain the emergence of contemporary humans.

Rather, we suggest that the existing complexity in ancient genomic

data and the evidence for multiple events and potentially extensive

genetic mixing of extinct populations in contemporary humans, in

dialogue with the archeological and fossil data, necessitates the use of

an expanded evolutionary toolkit.

Rather than relying solely on selection or gene flow models, it is

clear that genetic drift, niche construction and patterns of ecological

inheritance (plus increasingly complex models of cultural evolution)

were at play in shaping the genomes of populations of the genus

Homo (globally) during the terminal Pleistocene.9,35,52–54,94,113 Per-

haps, rather than identifying a suite of specific genetic changes/adap-

tations that made contemporary humans “more fit” than other populations, we could deploy the concept of a dynamic human

niche51,54,55,104 occupied by many populations of Homo, to varying

degrees of uniformity. Such an approach fits better with the current

conundrums presented by the genomic data.107 Under an EES model

niches change and are inherited. The plasticity of the human niche

(of which multiple populations of the genus Homo were a part)

suggests that we should expect extensive genetic structuring in

populations. As Premo and Hublin114 and Scerri et al.50 have shown,

structured populations may explain the low genetic diversity in con-

temporary humans, the patterns of complexity evident in the aDNA,

and the evidence for ancient genetic exchanges that we do have.107

The EES offers this broader toolkit with which to model such pro-

cesses and enables a more diverse engagement of all the paleo-data

with contemporary biology (see details below).

2.2.2 | What do “modern” humans look like?

What does it mean to be “modern” in the anatomical sense? It is far from clear which fossils should be placed into the category of Homo

sapiens, especially as many of the samples come from uncertain and

poorly dated contexts. Proponents of what Colin Renfrew has called

the Sapiens Paradox begin with the theory that behavioral modernity

happened after anatomical modernity. Klein,43,115,116 Hoffecker117

and others proposed various mechanisms for how this would occur.

But we need to be clear what is meant by anatomical modernity.

Hublin and colleagues118 drew distinctions between early anatomi-

cally modern humans and recent, but not contemporary, modern

humans. For these workers, samples such as LH 18, Omo 2, and

Qafzeh 6 & 9, are distinguished from mid-Pleistocene populations

such as the Neandertals by having a short face that is retraced under

the braincase. The brow ridge in particular has received much atten-

tion, partly due to the fact that its presence on Neandertals was an

obvious difference between that group and living humans. Other

researchers119,120 have argued that the Homo sapiens clade is defined

by a bipartite brow ridge, a small face with thin cranial bones, and a

vaulted neurocranium. A series of publications121,122 argued that the

brow of Neandertals and H. sapiens is very different. However,

Athreya123 has argued that only contemporary Homo sapiens stand

out in their brow ridge morphology, with other Homo taxa showing

overlap in metric traits. This suggests that the phylogenetic utility of

the frontal bone is questionable for most Pleistocene human fossils.

The human fossil record of the Middle Pleistocene has famously

been described as the “Muddle in the Middle.”124 There have been

KISSEL AND FUENTES 91

numerous proposed hominin species to account for the variation within

this sample125–127 including Homo heidelbergensis Homo erectus, Homo

rhodesiensis, Homo mauritanicus, and Homo helmei. Recent publications,

such as the announcement of Homo luzonensis6 from the Philippines and

Homo naledi128 from South Africa have demonstrated that the Middle

Pleistocene and the beginning of the Late Pleistocene may have been

more species rich, or at least morphologically dynamic, than previously

believed. These finds have tipped the balance in favor of the hypothesis

that Homo sapiens should not unilaterally be applied to fossils that are

simply younger than 300 ka.

One lesson from the last few decades is that there is a lot of mor-

phological diversity in Homo populations over the last 300 ka.

Schwartz129 takes this as evidence that we should not simply assume

that if a fossil is recent it must be Homo sapiens. If, according to

Schwartz, we define the H. sapiens clade with a true chin, a “ES” brow, a small lower face, and a tall, vaulted cranium then this may mean that

Neandertals and other clades should not be in the Homo group, and

thus we need to reestablish the genera rich ideas of the past. But, one

could ask why we need to do this at all? After all, we created the

Homo sapiens category, and when we continue to (re)define it as more

and more discrete are we accurately reflecting the available data? See-

ing human becoming as a process of expansion of the human niche

may help to answer the question by dismantling, rather than circum-

venting, morphological species definitions.

Two examples of this difficulty can be seen in the phylogenetic

significance of the Florisbad and Kabwe fossils. The Florisbad sample

includes the frontal bone and much of the right side of the face, and

part of the parietals, and the rM3 dated to 259,000 ± 35,000 bp. The

association between the molar and the rest of the material is unclear

and some have suggested that the ESR date for the molar may be

incorrect.130 The fossil was originally described by Dreyer131 who,

based on the width of the frontal bone and other “primitive” traits, proposed the name Homo (Africanthropus) helmei. As the Florisbad

skull was removed without modern excavation techniques, its associa-

tion with the archeological record is questionable. There is some evi-

dence to suggest that the fauna, including the hominin fossils, were

accumulated due to carnivore action.132 A wooded “implement” dated to around 121,000 ± 6,000 (though may be as old as the skull itself),

with alleged cutmarks on it was recovered during later excavations in

1952.133 Clark134 argued it was the lower end of a throwing club, an

assessment that may be correct, though difficult to prove.133

The Kabwe cranium, whose site has been mined away, was dis-

covered in 1921. Sadly, many of the associated artifacts and bones

(including a hominin clavicle) have been lost over the years. Clark135

excavated an area �250 yard from where the cave used to be and dis- covered a series of proto-Stillbay, Sangoan, and Achulean deposits.

The association of the fossils with each other is controversial136 and

the age and the context of the samples is uncertain. For example,

some interpretations suggest the bulk of the fossils are from a higher

level than the skull, which would in turn suggest that the fauna and

archeological remains may not be associated with the cranium.137

The cranium itself has a rather large cranial capacity, estimated at

1280 cm3, with an expanded midvault. Rightmire138 notes its large

cranial capacity and less strongly curved occipital suggests a different

form from H. erectus, arguing it either belongs to H. heidelbergensis

or H. rhodesiensis. The face is forwardly placed and has a heavy supra-

orbital torus and the cranial base is not as flexed as it is in most mod-

ern humans.139 Klein140 noted that the fauna are similar to those

from Upper Bed II through Bed IV at Olduvai. Millard141 used this

connection to date the deposits to no younger than 490 ka (though

depending on the dating one uses from Olduvai it could also be older

than 990 ka). Biostratigraphic data suggest it is similar in age to Bodo

and Elandsfontein (�800–600 kya). A recent study (published while this paper was in review) suggest a date of 299 ± 25 thousand

years.142

There were also several bone tools reported.137 These tools were

noted by White in his 1908 description of the materials. However,

many of them have subsequently been lost. Barham and colleagues143

located three bone tools from the collections. Clark also notes the

presence of a “One small piece of weathered haematite”137 that seems to have been brought into the cave, though he notes there is

no use-wear on it (as far as we know, this piece has been lost).

As both these crania suggest, it is currently difficult to trace a

clear “path” as to which fossils belong to the Homo sapiens clade. While many would question if either are in the H. sapiens sample, the

problematic nature of their dating suggests that we have a tendency

to conflate modernity with recency. For example, the re-dating of the

Jebel Irhoud shows this well. Originally argued to be Neandertal,144

new TL dates place the sample at �300 ka. This, alongside morpho- logical features of the face, has scholars claiming it is H. sapiens.118

“Even approximately 300 ka ago their facial morphology is almost indistinguishable from that of more RMH (recent modern humans),

corroborating the interpretation of the fragmentary specimen from

Florisbad (South Africa) as a primitive H. sapiens tentatively dated to

260 ka.”118

It is unclear just how useful phrases like “primitive,” “early ana- tomically modern humans,” “archaic humans” etc… really are. Writing in 1995, Tobias noted:

“Yet many investigators have continued to use this term, ‘anatomically modem humans’, as though it could be applied to all living and recent human beings, that

is, to all members of the living subspecies H. sapiens

sapiens. This author pleads guilty to using the term

unthinkingly not long ago (Tobias 1992). If the term

cannot be defined it should be discarded (Wolpoff

1986). Instead of speaking of ‘anatomically modern human beings’, we should speak of ‘modern’ or ‘recent’ humans, using a temporal not a morphological descriptor (Tobias 1993). After all, we are not in the

habit of speaking of ‘anatomically modern elephants’ or ‘anatomically modern hippopotami.’”145

While we agree that it is a problematic term, we would extend

Tobias' comments to the notion of modern as well. What makes a

fossil modern does not seem to have a strict definition. Much like

92 KISSEL AND FUENTES

thinking about modern human behavior, modern human anatomy has

implications beyond the quest to find the first appearance of our spe-

cies. We need to ask modern to whom? Or in comparison to what?

The history of the field146–148 has shown that paleoanthropologists

have often been complicit in racist, sexist, and colonialist narratives,

with “modern” being synonymous with “advanced” and deployed to other and de-humanize non-European groups.

According to Schwartz129 the idea that chronology should take

precedence over morphology is what lead to terms like “archaic” and “anatomically modern.” Allocating specimens to one group or the other has become almost arbitrary. In theory, the archaic group were

distinguished from the AMH group by being more robust with larger

faces and jaws, but this is not often quantified. For Schwartz, no

archaic specimen has anything like the brow ridge seen in extant

Homo sapiens. But what does this tell us? Should we expect a sample

that lived over 200 ka look similar to humans today, especially in light

of morphological changes in the Holocene? A better question is what

patterns of variation looked like in the past versus the patterns of var-

iation that we see now.

Wolpoff and Caspari149 ask if modern features on a fossil make the

sample modern. As they note, if you assume that modern humans are a

distinct species then these features may imply modernity. However, that

assumption is one that we might question. As shown by Ackermann and

colleagues113 many “species” (that is, fossil populations of the genus Homo) have hybridized over the Pleistocene. This can lead to different

behaviors and morphs of populations. As Wolpoff and Caspari note

“The main problem with modernity, we think, is reflected in the fact that there is no worldwide definition of moderns that simultaneously

includes all modern humans and excludes all archaics.”149

If human behavior arose over the long term and was critical in

shaping, and being shaped by, human morphology; if there was a slow

burn to Homo sapiens, then we might expect to find samples with a

mixture of modern and archaic features. As noted above, the criteria

dividing “true human” from “not-quite human” is ever-changing. Stud- ies of introgression between Late Pleistocene populations in Eurasia

has shown multiple hybridization events.47,62,113,150

As noted recently by Smith and Wood, “Every snowflake that has ever fallen is different from every other one. Every modern human is

different from every other modern human. But this does not stop us

from studying snowflakes or modern humans as groups.”151 They go on to note that the task of studying the twigs on the Tree of Life

exposes us to both ask, and also attempt to answer, unrealistic ques-

tions. “There is much we would like to know about human evolution- ary history, but wanting to know something does not make it

knowable.”151 Attempting to find the moment hominins morphologi- cally became Homo sapiens, while possibly a laudable goal, is compli-

cated by the fact that any claim of the earliest trait/behavior/tool will,

as the history of the field attests, be soon replaced by yet another

spectacular find.

If we move away from a focus on specific cranial morphological

plasticity/variation in Homo as needing to reflect some form of cana-

lized adaptive significance or a sign of mating isolation to demarcate

species boundaries dividing “modern” and “archaic” we can shift to a

view of such plasticity as part of the processes of the Homo niche.

It may be that the dynamics of such plasticity in cranial (and post-

cranial) morphology acted as a crucial template of constraints and

affordances facilitating aspects of the broad ecological and behavioral

expansions and innovations we see in the terminal Pleistocene Homo

populations across much of the world.

2.2.3 | Are “art” and symbol creation/use “modern”?

What, then, does modern human behavior mean? While we are guilty

of using that phrase, we agree with Shea8 and others that it is prob-

lematic. It is also regressive. Being human is not a matter of being able

to engrave on various media. Not all humans do these things today,

yet all contemporary Homo sapiens are fully modern humans. Leslie

White argued that the symbol was the basic unit of human behavior:

“Man uses symbols; no other creature does. A creature either uses symbols or he does not; there are no intermediate stages.” To prove his point, White points to “rare cases of children who grew up without symbols because of deafness and blindness, such as those of Laura

Bridgman, Helen Keller and Marie Heurtin, are instructive. Until they

‘got the idea’ of symbolic communication they were not human beings, but animals, they did not participate in behavior which is

peculiar to human beings. They were ‘in’ human society as dogs are, but they were not of human society.”.152 This type of ableist exceptionalism would not be accepted by scholars today. However,

paleoanthropologists still often assume that symbolic thought is a

“you-have-it-or-you-do-not” trait, leaving us with a mentality that sees these differences as facts of nature rather than aspects of histori-

cal and cultural processes. Recent research refutes this view. The

processes of becoming human, in the aspects of the creation of

meaning-laden materials, are far more complex than previously

believed. We find evidence of engravings on clam shells by

430,000 ya,153 ornamentation by 130 ka,154 ochre at 200 ka,155 and

“art” by �300–200 ka.156,157 All of these examples come from sites/ populations/samples not usually considered to be created by H. sapi-

ens. Creative human behaviors are more common, and older, than once

believed.

As with the fossil and genetic data, we cannot pinpoint the

moment our species became behaviorally modern. This is because the

niche of behavioral modernity has not stopped evolving. As we have

argued previously45 the move to identify “symbolic” behavior before 100,000 ya is complicated by the lack of detailed information about

the culture that created these artifacts. After 100,000 years ago mate-

rials classified as “symbolic” such as beads, engraved objects, ochre, etc. due to their recognizability as contemporary human symbols

begin to make up a significant component of the material lives of

many members of the genus Homo. But, as we and others have

argued, calling them ‘symbols’ is problematic.45,158–160 From a semi- otic perspective, a sign is symbolic if the connection between it

and whatever it stands for is based on convention, rather than by

similarity (iconic) or contiguity (indexical). For example, everyone

KISSEL AND FUENTES 93

agrees/learns that a red light means stop rather than red meaning

‘stop’ due to its intrinsic properties. Humans communicate with and through signs. We can ask how

specific signs such as beads, engraved ochres, and pendants func-

tioned without giving a culturally-laden meaning to them.

However, to know if something is a symbol we must be aware of

the cultural context it was created in, something we do not have

access to or most of the Pleistocene. We simply do not have access to

the systems of meaning (cultures) of Pleistocene populations of the

genus Homo. In its place, we argue we should think about how a

sign functions by itself, which requires a different type of semiotic

analysis.45,161

Centering questions not on what these objects meant to early

humans, but rather how they were able to mean something, may allow

us to escape the constant debate about whether something is or is

not symbolic, and thus move away from the “symbol” as the dividing line between “modern” and other humans. As Wilkins writes in regard to stone tool typologies “Lithicists structure their research according to NASTIES, not necessarily because it is meaningful or useful, but

because we are building on a long tradition of doing it that way.”44

It might be useful to refer to different classes of objects as symbolic

but that does not mean that it can help to answer the questions we

currently have about Pleistocene populations. The ability to create

objects that not only have meaning, but that are created with the

intent to produce a specific meaning/response in the mind of another

person, is a critical part of the human niche and shows up in a dynamic

range of places, times, and populations across the Pleistocene.

We suggest moving our focus away from the “symbol” and the explanation of potential fitness enhancing benefits it offers and

toward the details of how, when and where evidence of meaning

making (via material remains) appears associated with populations

of Homo. If we do this, and connect the data from such an approach

to the concepts of niche construction and multiple modes of evolu-

tionarily relevant inheritance, we leave space open for models of

reciprocal causation between meaning-making activities, bodies and

ecologies. In such scenarios fitness enhancing outcomes may arise

from multiple processes but do so as components of a larger ongoing

dynamic including ecological and behavioral inheritances and neurobi-

ological and cognitive feedback cycles featuring complex relationships

between behavior, morphology, intra- and intergroup interactions and

a myriad of potential social ecologies.

2.3 | Becoming human: Connecting the dots via the EES

Contemporary evolutionary theory, in the form of the Extended Evo-

lutionary Synthesis (EES), does not limit evolutionary inquiry to a

focus on natural selection as the sole architect of function. It does

not negate the central role of selection but does not isolate it as the

point of validity, the key explanandum, for evolutionary models.

Rather, such an approach assumes diverse and multiple evolutionary

processes as the baseline for inquiry into evolving systems. In doing

so one does not focus only on a single mode or level of evolution (bio-

logical and cultural, genic, individual and group), but includes a plural-

ity of evolutionary processes, from selection to niche construction

to developmental plasticity, and others, as potentially mutually inter-

acting in evolutionarily relevant and reciprocally causal or mutually

influential modes, and thus relevant in the analyses of evolutionary

patterns and trajectories.

We have argued that the genetic, fossil and archeological data

indicate that the search for a line defining, or specific point for, mod-

ern humans is problematic. This, we argue, is why the EES can be a

beneficial frame for investigating human evolution. By deploying a

toolkit that enables us to think about human evolution in the holistic,

and integrative, sense we remember that humans not only make tools,

create symbols and alter ecologies, we inherit them; creating new

landscapes of selection and structures of affordances and constraints

that we shape and are shaped by. Such processes need to be included

in models of human evolution. Our morphologies, physiologies and

neurobiologies are enmeshed in a dynamic suite of processes that

resists simple analyses and defies, in many cases, straightforward

adaptive-trait explanations and models.

The search for our origin is complicated by the very nature of

the question. Contemporary human behavior is very different from

the human behavior of 200,000 years ago and of 30,000 years ago.8

Changes in how humans obtain food, adaptations to local environ-

ments, and the acceleration of human evolution162 have produced

remarkable changes in the human phenotype and genotype such that

what we might call modernity now is different from what we could

honestly call modernity even in the recent past. Rather than try to find

ways around this complication, the EES lets us embrace this.

The human niche is embodied as humans navigate social and eco-

logical landscapes. Human bodies and minds acquire particular motor

and social skills in a particular context, which includes a set of beliefs,

ideologies, practices, materials and meanings. Humans embody the

specifics of a language, particular modes of movement and behavior,

appropriate mannerisms, and the use of and interface with clothing,

food, and patterns of socializing, rules, laws, and customs. Humans are

also immersed in the beliefs and practices of their home community

and are influenced by those of the places and peoples they encounter.

Human minds and bodies are shaped by all of these experiences. This

is as true today as it was in the past, but it did not emerge fully-blown.

Such a niche evolved.

If becoming human is indeed a process, then the concept of a

Rubicon or some defining line, which, once passed, makes us human,

becomes less important. The greater importance then lies in modeling

the processes in which the human niche emerges, functions and

changes across time and how those patterns relate to the material evi-

dence (bones/fossils, DNA sequences, and archeological artifacts)

paleoanthropologists work with. Expanding on selection-focused and

inter-population or inter-specific contest models of human evolution

via the incorporation of the EES facilitates a more dynamic, and likely

more accurate, lens and toolkit.

Debating which members of later Pleistocene Homo are “really” human has not proven to be a particularly successful, or scientifically

94 KISSEL AND FUENTES

viable, endeavor. Moving toward the understanding of processes and

patterns of a human niche and away from definitional tropes of “mod- ern” or not better fit the current datasets. Such approaches place paleoanthropological inquiry in more intensive dialogue with contem-

porary evolutionary theory and a broader anthropological practice,

thus getting us closer to a better science of why and how we are

human.

ACKNOWLEDGMENTS

We thank Robert Benitez and John Murray for inviting us to the SAA

symposium that produced this volume and all the participants of the

session for their thought-provoking and stimulating discussions. We

also thank the three reviewers for their extensive and insightful com-

ments and critiques on the various versions of this paper. Thanks to

Jacob Heller for comments on the manuscript draft, John Hawks for

use of the images, and Princeton University, the University of Notre

Dame and Appalachian State University for support while writing this

paper.

DATA AVAILABILITY STATEMENT

Data sharing is not applicable to this article as no new data were cre-

ated or analyzed in this study.

ORCID

Marc Kissel https://orcid.org/0000-0002-4004-1996

AgustÍn Fuentes https://orcid.org/0000-0003-0955-8214

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AUTHOR BIOGRAPHIES

Marc Kissel is an assistant professor of anthropology at Appalachian

State University where he works on the evolution of human symbolic

thought and the evolutionary arc of human warfare. His latest book is

Emergent Warfare in the Evolutionary Past (Routledge) co-written with

Nam Kim.

Agustín Fuentes is a Professor of Anthropology at Princeton Univer-

sity. His current foci include cooperation and creativity in human evo-

lution, ethnoprimatology and multispecies anthropology, evolutionary

theory, and public perceptions of, and interdisciplinary approaches to,

human nature(s). His latest book is Why We Believe: evolution and the

human way of being (Yale).

How to cite this article: Kissel M, Fuentes A. The ripples of

modernity: How we can extend paleoanthropology with the

extended evolutionary synthesis. Evolutionary Anthropology.

2021;30:84–98. https://doi.org/10.1002/evan.21883

98 KISSEL AND FUENTES