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Beyond the here and now: hunter–
gatherer socio-spatial complexity and the
evolution oflanguage
Brian M. Wood1,2, David A. Raichlen3, Herman Pontzer4,5, Jacob A. Harris6, M.
Katherine Sayre7, Bunga Paolo8, Mariamu Anyawire8 and Audax Z. P. Mabulla9
1Department of Anthropology, University of California, Los Angeles, CA, USA
2Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology,
Leipzig, Germany
3Department of Biological Sciences and Anthropology, University of Southern California, Los Angeles, USA
4Department of Evolutionary Anthropology, and 5Duke Global Health Institute, Duke University, Durham, NC, USA
6School of Interdisciplinary Forensics, Arizona State University, Tempe, AZ, USA
7Department of Anthropology, University of California, Santa Barbara, CA, USA
8Hadza fund, Mangola, Tanzania
9Department of Archaeology and Heritage, University of Dar es Salaam, Dar es Salaam, Tanzania
BMW,0000-0002-8187-9429; DAR,0000-0002-4940-7886; HP,0000-0003-2397-6543;
JAH,0000-0001-5398-7871; MKS,0000-0003-2554-4058; AZPM,0000-0001-9591-5497
Human evolutionary ecology stands to benefit by integrating theory
and methods developed in movement ecology, and in turn, to make
contributions to the broader field of movement ecology by leveraging
our species’ distinct attributes. In this paper, we review data and
evolutionary models suggesting that major changes in socio-spatial
behaviour accompanied the evolution of language. To illustrate and explore
these issues, we present a comparison of GPS measures of the socio-spatial
behaviour of Hadza hunter–gatherers of northern Tanzania to those of olive
baboons (Papio anubis), a comparatively small-brained primate that is also
savanna-adapted. While standard spatial metrics show modest differences,
measures of spatial diversity, landscape exploration and spatiotemporal
displacement between individuals differ markedly. Groups of Hadza
foragers rapidly accumulate a vast, diverse knowledge pool about places
and things over the horizon, contrasting with the baboon’s narrower
and more homogeneous pool of ecological information. The larger and
more complex socio-spatial world illustrated by the Hadza is one where
heightened cognitive abilities for spatial and episodic memory, navigation,
perspective taking and communication about things beyond the here and
now all have clear value.
This article is part of the theme issue ‘The spatial–social interface: a
theoretical and empirical integration’.
1. Introduction
Evolutionary anthropologists, linguists and cognitive scientists have
suggested that changes in socio-spatial behaviour accompanied the evolu-
tion of key attributes of Homo sapiens, including our large brains, advanced
cognitive capabilities and language [1–3]. These evolutionary models motivate
research into functional relationships between spatial behaviour, social
structure, cognition and communication, aligned with the socio-spatial
interface framework advocated by Webber et al. [4]. Humans and our hominin
ancestors are extreme outliers in our dependence on socially transmitted
information [5]. Following the causal paths outlined by Webber et al. [4],
we thus expect distinct patterns of spatial behaviour to have emerged in
© 2024 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution
License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original
author and source are credited.
Research
Cite this article: Wood BM, Raichlen DA, Pontzer
H, Harris JA, Sayre MK, Paolo B, Anyawire M,
Mabulla AZP. 2024 Beyond the here and now:
hunter–gatherer socio-spatial complexity and the
evolution of language. Phil. Trans. R. Soc. B 379:
20220521.
https://doi.org/10.1098/rstb.2022.0521
Received: 16 January 2024
Accepted: 15 July 2024
One contribution of 14 to a theme issue ‘The
spatial–social interface: a theoretical and
empirical integration’.
Subject Areas:
behaviour, evolution
Keywords:
hunter–gatherers, human movement ecology,
displacement, Hadza, olive baboon, evolution of
language
Author for correspondence:
Brian M. Wood
e-mail: brianwood1@gmail.com
our species, relative to other primates. Specifically, we hypothesize that patterns of spatial behaviour have arisen that facilitate
increased collection and sharing of ecological information. To examine this idea, Part 1 of this paper presents a targeted
review of relevant theory and data. In Part 2, we provide an empirical comparison, using GPS data collected at a similar scale
and resolution, of the movement and interaction patterns of human hunter–gatherers and olive baboons living in a similar
savanna–woodland habitat.
(a) Part I: the evolution of human spatial behaviour and language
Reconstructing the evolution of hominin spatial behaviour is challenging because data attesting to ancestral human landscape
use is scant and fragmentary. Tentative models of the past are built through a merging of theory with data derived from
studies of primatology, fossil anatomy, geology, archaeology and ethnography. Primatological research documents the range
of challenges that early hominins likely confronted, inspiring hypotheses about how adaptations to these challenges shaped
human evolution. Studies of great apes are particularly relevant for phylogenetic reconstructions of early hominins.
Chimpanzees, bonobos and gorillas all specialize in acquiring ripe fruit and prefer rainforest habitats with short dry seasons
[6]. The last common ancestor of humans and African apes likely had similar dietary and habitat preferences [7]. Since the Late
Miocene, global cooling, drying and increased seasonality have led to the spread of grasslands and open woodlands across
much of Africa [8]. Stable carbon isotopes from fossil soils indicate that over the past 6 million years, hominins in eastern Africa
lived in open environments with less than 40% woody cover [9].
Remains of early hominins in the period between 7 and 4 Mya have been found in central and east Africa, and have
been placed within the genera Sahelanthropus, Orrorin and Ardipithecus [10,11]. Anatomical interpretations of these earliest
hominins remain a focus of debate, but they appear to have been bipedal, with the skulls of Sahelanthropus and Ardipithecus
indicating great ape-sized brains [12,13]. Unambiguous evidence for bipedalism is found in the anatomy of Australopithecus
species after 4 Mya [14]. When modelling how these early hominins made a living and ranged through landscapes, large
primates living in open environments are especially relevant. In a less fruit-rich environment, one strategy is to consume large
amounts of lower-quality vegetation. When facing seasonal fruit shortfalls, mountain gorillas, for instance, focus on abundant
but low-quality fibrous leaves and terrestrial herbaceous vegetation (THV) and maintain smaller daily travel distances than
other apes [15–18]. A similar strategy might have been adopted by the megadont hominin Paranthropus group (3–1 Mya), which
likely exploited low-quality C4 vegetation [19,20].
Another strategy in response to decreased fruit abundance is to expand one’s search for higher quality foods. Evidence for
an analogous strategy is seen in comparisons of chimpanzee communities. Compared with those living in fruit-rich rainforests,
chimpanzees at the far western and eastern edges of the species’ range, in the savanna woodlands of Senegal and Tanzania (Mt.
Assarik, Fongoli and Ugalla, Tanzania), cover more territory and have the largest home ranges recorded for any non-human
primate [21,22].
Baboons are also a widely used primate model for early hominins [23,24]. They are an apt model for considering the
ranging and sociality of australopithecines because both taxa are large-bodied, sexually dimorphic, catarrhine primates [25].
Olive baboons are ecologically diverse and widespread, inhabiting both forest and savanna habitats across Africa. Many
Australopithecus remains have been recovered from the East African Rift Valley [26], a region where today baboons thrive, and
no great ape populations are found. For thinking about how the risks, resources and physical features of this habitat would
have influenced the spatial and social behaviour of australopithecines, further consideration of the baboon model is warranted.
Comparing the spatial behaviour of humans and baboons today may provide insights into how our species’ unique cognitive
abilities, technologies and language have changed the manner in which we make adaptive use of these landscapes, relative to a
more primitive ancestral species.
Language is our species’ most distinctive adaptation [27]. A core feature of language is that it permits efficient communi-
cation about spatially and temporally remote events beyond the here and now [28–30]. The linguist Charles Hockett [30]
argued that an exceptional feature of human language was its capacity for displacement—the ability to communicate about
things that are out of sight or in the past or future. By contrast, signals used in non-human communication systems typically
refer to things in the immediate environment of the sender or receiver, such as the presence of a predator or a food source.
Hockett considered some capacity for displaced communication to be a key precursor to the development of more complex
symbolic communication. More recently, linguist Derek Bickerton [29] highlighted the extreme rarity of displacement in animal
communication systems. He argued that this feature was pivotal in the early evolution of human language. Bickerton proposed
that the capacity for displacement likely evolved for sharing information about food sources located beyond the direct sensory
perception of message recipients. Displacement is the feature of language we focus on here because it refers to the where and
when of meanings being expressed in language, and the adaptive benefits of this rare, essential language feature hinge on how
individuals interact across space and time. We hypothesize that this core feature of language is necessary only in social groups
where individuals interact with others who have recently acquired dissimilar ecological and spatial information. Below, we test
the prediction that human hunter–gatherer movement patterns more strongly satisfy this criterion than those observed in olive
baboons.
(b) Part 2: human hunter–gatherer and olive baboon movement patterns
Motivated by an interest in spatial information acquisition and sharing, we use GPS measures to estimate the spatial informa-
tion that individuals are exposed to. Strandburg-Peshkin et al. [31] deployed GPS collars and tracked the movement of a troop
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of olive baboons at Kenya’s Mpala field station over 14 days, and then shared the GPS data publicly via moveBank [32]. These
baboon movement data now provide a valuable benchmark for cross-species and cross-community comparisons. No such data
are available for any great ape. The Hadza hunter–gatherer GPS data that we analyse here is the same sample used in Wood
et al. [33], which records the movement of 179 Hadza research participants (87 females and 92 males) over 2048 person-days
of travel, ranging in age from 2 to 84 years (mean = 36, s.d. = 19). We refer readers to that open-access publication for full
details of the sample and methods. In studies of people, ethical considerations limit the open distribution of detailed location
data, highlighting the importance of quantitative, standardized data summaries in order to balance the goals of knowledge
dissemination with privacy and ethical concerns.
2. Results
We next compare measures of daily travel, inter-individual proximity, inter-individual differences in exposure to spatial
information and collective measures of landscape exploration.
(a) Daily travel and inter-individual proximity
The average day range for the Mpala baboons was 10.58 km (n = 250, s.d. = 1.81), higher than the day ranges reported for this
species in prior research [34], likely owing to the high temporal resolution of the GPS data. This value is quite similar to the
average day range of adult Hadza, which is 11 km on average for adults (males and females combined) between the ages of
18 and 50 [33]. In figure 1, we plot the track of the baboon whose day range most closely matched the sample average and her
proximity to other group members throughout the day.
The Mpala baboons were central place foragers whose travel was usually tethered to the sleeping sites from which they
departed in the morning and returned at the end of the day. Across the baboon sample, the median distance between a day’s
start and end points of travel was only 58 m (s.d. = 85). Olive baboon sleeping sites are usually carefully selected for their safety
and proximity to water and are often on cliffs or high in trees, where group members are afforded greater visibility and safety
from predators [35].
In an early study of wild baboons, Washburn & DeVore [36] wrote that ‘whether by day or night, individual baboons do
not wander away from the troop, even for a few hours ... once an animal is separated from the troop the chances of death are
high’ (ibid: 66). Indeed, the Mpala baboons seldom ventured far from one another (figure 1b). In the baboon sample, the median
inter-individual distance was 23.1 m (mean = 33.5, s.d. = 32.9, max = 407.2, n = 18 881 268). Among the Hadza, the median
inter-individual distance was 301.5 m (figure 2a; mean = 1545.8, s.d. = 2341.2, max = 17 347.3, n = 106 429 818).
In Hadza settlements, or camps, it is normal for people to depart camp in the early morning, travelling in parties of variable
sizes, searching for and harvesting resources, followed by a return to camp in the afternoon or evening. A small subset of camp
members might stay in the bush hunting all night, or leave on short visits to neighbouring camps [37]. These typical patterns
of movement mean that the splitting and merging of Hadza social groups, reflected in inter-individual proximities, are highly
structured across time, forming a general pattern of early day aggregation, daytime dispersal and evening re-aggregation. This
forms a notable contrast with baboons, where cohesive groups are observed across all hours of the day (figure 2b); there is even
a trend seen in the baboon GPS data of greater dispersion at dawn and in the evening.
Hadza camps are inviting places where a range of activities occur including rest, food preparation, meals, childcare,
socializing, play, tool maintenance, conversation and storytelling [37]. The importance of these in-camp social activities is
reflected in the greater amount of time that Hadza spent very near their day’s first GPS point, which was usually at the wearer’s
hearth (figure 3). Twenty-five per cent of the Hadza’s total GPS points (i.e. 25% of their total observed time) was within 24 m of
their day’s starting point, and 50% of their total time was spent within 88 m of this point (figure 3).
By contrast, in the olive baboon sample, the first quartile of their recorded distances extends to locations 243 m distant from
their day’s starting point, and the median logged distance was 679 m from that point. These data also attest to how much further
the Hadza travel from their ‘central places’. No baboon travelled further than 2.1 km from their day’s starting point, whereas
17% of the Hadza’s time was spent in locations more distant than this, and the maximum distance reached by a Hadza in this
sample was 12.8 km. In summary, these data show that Hadza both spend more time very close to their central place and more
time very far from that place (figure 3).
(b) Inter-individual differences in exposure to spatial information
Here we present measures of whether individuals explore the same or different parts of the landscape on each day, which
we consider a proxy for differences in exposure to spatial and ecological information. These analyses are based on raster
representations of the landscape, in which we record every 10 m2 cell visited by each individual, each day. For each dyad on
each day, the fraction of their landscape use that is shared is that fraction of the total visited landscape that was visited by both
individuals, and the fraction that is different is that proportion which was visited by one of the dyad members but not both. Our
calculations show that dyads of Mpala olive baboons are much more similar in their patterns of landscape use and exposure to
spatial information than are dyads of Hadza hunter–gatherers. The median shared fraction of the landscape visited per day was
0.35 in the Mpala baboon dyads and just 0.04 in the Hadza dyads (figure 4).
These data show that Hadza who live in the same camp experience much greater spatial displacement from one another
each day (figure 2) and that dyads of Hadza who live and interact daily in the same group visit highly distinct areas of the
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landscape, relative to baboons (figure 4). This confirms our prediction that within Hadza groups, individuals would acquire
more individually distinct (i.e. dissimilar) sets of spatial and ecological information. The Hadza’s spatial behaviour thus creates
more possibilities for individuals to share information that is novel to others, because it was beyond others’ range of travel and
direct sensory perception that day.
UTM Northing
39400
39000
(a)
Hour of Day
300 m
38600
268100
268500
UTM Easting
06
07
08
09
10
11
12
13
14
15
16
17
268900
Distance (m)
100
200
300
06:00
09:00
12:00
15:00
18:00
Time
(b)
Figure 1. (a) The path of an adult female olive baboon at Mpala who travelled 10.6 km on 12 August 2012, over the course of 12 h. Her path on this day began at
the location indicated by the red dot and ended at that shown by the blue dot, only 20 m distant. (b) Proximity between this female and all other group members
throughout the day, sampled at 10-min intervals for visual clarity. Each line in (b) represents her proximity to a different group member.
15000
Hadza Inter-Individual Distance by Hour
Quantile
Max
Inter-Individual Distance (m)
10000
5000
0
6 7 8 9 10 11 12 13 14 15 16 17 18
Hour of Day
6 7 8 9 10 11 12 13 14 15 16 17 18
Hour of Day
400
Baboon Inter-Individual Distance by Hour
Median
Q25
Q75
Q95
Inter-Individual Distance (m)
300
200
100
0
Quantile
Max
Median
Q25
Q75
Q95
(a) (b)
Figure 2. (a) Hadza inter-individual proximities by hour (n = 102 854 437) and (b) Mpala baboon inter-individual proximities by hour (n = 18 881 268). Please note
the large difference in y-axis scales.
Distance (m)
10000
5000
–5000
–10000
0
10000
5000
–5000
–10000
0
Hadza Hunter–Gatherers
–10000 –5000 0
Distance (m)
5000 10000 –10000 –5000 0
Distance (m)
5000 10000
Mpala Baboons
(a) (b)
Figure 3. Time spent at different distances from each day’s starting point in the Hadza hunter–gatherer and Mpala baboon samples. The black circles in the centre
of each plot encompass 50% of all GPS points, i.e. 50% of all recorded time, of each sample. The white circles encompass 75% of all GPS points, and the blue circles
encompass 100% of each sample.
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(c) Collective measures of landscape exploration
We next consider how spatial exploration, and by extension, ecological and spatial information, accumulates in the group across
individuals. We calculated the cumulative sum of the total unique land visited each day, progressively considering how this
value changes as we sum from 1 to N individuals whose travel was monitored each day.
The cohesive ranging of baboons creates a relatively homogeneous spatial and ecological experience for group members.
The low slope of the trend line in figure 5a means that additional group members provide little gain in spatial exposure, or
by extension, unique spatial knowledge, at the collective level. Conversely, the Hadza’s more diverse travel results in a much
steeper gain of exposure to unique areas of the landscape, producing a larger and more diverse pool of spatial information at
the group level.
(d) Sex differences in landscape use
A sexual division of labour, in which each gender is associated with different economic roles, is a universal feature of hunter–
gatherer societies [38,39]. The sexual division of labour is one factor that helps explain why hunter–gatherers like the Hadza
are expected to exhibit greater intra-group diversity in patterns of landscape use compared to non-human primates. Hadza men
focus on hunting more widely dispersed and mobile resources (mammals, birds and wild bee colonies), whereas Hadza women
focus on gathering immobile and more abundant plant resources (tubers, fruit and greens). A prior study of Hadza movement
ecology [33] found that the paths that women followed while foraging out of camp were shorter and more linear, while those
of Hadza men were longer and more sinuous. Here, we present a comparison of geographic segregation by sex/gender. Using
raster analysis, we calculated the total landscape visited and then partitioned it into the fraction only visited by males, only
visited by females, and that visited by both males and females.
Fraction of Visited Landscape
Hadza Dyads Baboon Dyads
1.00 1.00
0.75
0.50
0.25
0.00
0.75
0.50
0.25
0.00
Different Shared Different Shared
(a) (b)
Figure 4. Dyadic measures of similarity and difference in daily landscape use by (a) Hadza hunter–gatherers (n = 13 656 dyads) and (b) Mpala baboons (n = 2240
dyads). See §4d for details of how these values were calculated.
(a)(b)
Unique Land Explored (km2)
0.5
1.5
1.0
0.0
0
Mpala Baboons
10 20
N Individuals
30
1.5
1.0
0.5
0.0
Hadza Hunter-Gatherers
0 10
N Individuals
20 30
Figure 5. The cumulative amount of unique land explored per day, as a function of group size. Each line represents a unique calendar day, and its slope represents the
relationship between the unique land explored and additional group members. The black line represents a generalized additive model of the expected trend, fit to the
data using a cubic spline.
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Figure 6 shows that gender strongly structures patterns of Hadza landscape use, and on average only 13.6% of the total
landscape visited was visited by both males and females. This pattern arises because Hadza men travelled further, and usually
travelled alone, whereas Hadza women travelled in groups and to fewer areas of the landscape [33]. Sex is much less predictive
of landscape use in baboons, and both males and females visited 79.1% of the total visited landscape at Mpala.
3. Discussion and conclusion
While both Hadza hunter–gatherers and Mpala baboons inhabit similar environments in the Rift Valley and engage in central
place foraging with similar daily travel distances, notable differences exist in their social interactions, travel diversity and the
accumulation of spatial and ecological knowledge at the group level. The Hadza’s diverse travel patterns create opportunities
for frequent interactions where individuals can share ecological information that others are unaware of. By contrast, among
Mpala baboons, the ‘ecological news’ gathered by one group member is largely equivalent to others’. The evolution of more
Hadza-like patterns, we suggest, would generate conditions more conducive to communication about places and events beyond
the here and now, a key adaptive feature of language.
The scenario we envision as conducive to the evolution of language involves central place foragers who travel widely and
disperse during the day, and then aggregate afterwards. Under what conditions would it be beneficial for such individuals
to share ecological information? We have not focused on that question here, but Bickerton [29] argued that a hominin dietary
shift towards more hunting and scavenging would have generated new opportunities for mutualistic cooperation, and thus a
context where individuals who could communicate with and recruit conspecifics for the defence, processing and carrying of
large animal carcasses would benefit. Because hunter–gatherers cooperate in many foraging activities, the evolution of language
to coordinate joint action for harvesting resources is a compelling idea [40–42]. Theoretically, one can imagine different temporal
and spatial scales of dispersal and aggregation, different sorts of ecological features and adaptive challenges that may warrant
cooperation and communication, and differences in the social composition of groups that would impact the costs and benefits
of sharing news. This is all ripe territory for modelling, and agent-based models of social learning and information transmission
are well suited to exploring these possibilities (e.g. Garg et al. [43]).
How did the highly diverse ranging patterns of hunter–gatherers arise? As noted by Marlowe [44], the evolution of technol-
ogy—including sharpened sticks, pikes and spears would have improved hominin extractive foraging and hunting, predator
defence and likely changed patterns of travel. The Hadza’s bows, arrows, knives, axes and digging sticks both make their
hunting and gathering more effective and protect them from the same predators that afflict baboons. The development of
such technologies is likely to have co-evolved with greater individual spatial autonomy and socio-spatial diversity, and thus,
generated more contexts for the adaptive sharing of ecological information, recruitment and spatial coordination in general.
A shift towards more technologically aided extractive foraging is likely to have also selected for larger brains [1]. Rosati [45]
provides several examples of how foraging strategies predict cognitive traits of primates and calls for renewed attention to
how diet, foraging strategies, and ranging behaviours might influence cognition. Rosati also notes that human hunter–gatherers
appear exceptional in terms of their ranging and the degree to which socially acquired information (culture) is employed in
foraging strategies.
Language and storytelling are human universals, and many ethnographic studies have documented storytelling in hunter–
gatherer camps (e.g. [46]). Marlowe describes Hadza storytelling as both a form of entertainment and a way to convey vital
information [37, p 66]. Scalise Sugiyama [47] argues that acquiring locally adapted foraging knowledge is a key function of
narrative storytelling in hunter–gatherers. In her study of Ju/’hoansi storytelling, Wiessner [48] notes that economic plans are
a frequent topic discussed during daylight hours and that events of the day are also retold by firelight at night. In their study
of Agta storytelling, Smith et al. [49] note that narrative stories often convey messages that are important for coordinating
behaviour and planning foraging activities. These observations align closely with our experiences in Hadza camps, where,
regardless of one’s luck in foraging, everyone returns to camp with a story to share.
Males
only
8.3%
Females
only
12.6%
Both males
and females
79.1%
Olive Baboons
Females
only
10.9%
Males
only
75.5%
Both
genders
13.6%
Hadza Hunter-Gatherers
Figure 6. Similarity and difference in landscape use, aggregated by gender/sex. The Hadza measures are the average values in a study of 12 camps [33].
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4. Material and method
All the code needed to reproduce this paper’s figures and text-reported results are shared via the Open Science Foundation
(https://osf.io/c6gr5/ and doi: 10.17605/OSF.IO/C6GR5).
(a) Hadza GPS data
Before participating in the study, all participants were informed about the research and gave their consent. This research
received authorization from the Institutional Review Boards at Harvard University, Yale University, Hunter College, the
University of Arizona and the University of California, Los Angeles, as well as from the Tanzania Commission for Science
and Technology and the National Institute for Medical Research in Tanzania. GPS data were collected in 15 Hadza camps
between 2005 and 2018 where the residents were subsisting from hunting and gathering for the vast majority of their diet (figure
7). The sample includes 2078 person-days of travel, and 179 participants (87 female, 92 male, mean age = 36). The GPS data
record individuals’ locations every 5 s. On average, devices were put on at 07:46 and stopped recording at 18:58. Full details of
the methods are shared in open-access publication Wood et al. [33].
(b) Mpala olive baboon GPS data
The baboon GPS data were collected in August 2012 and shared in moveBank. The original raw data recorded individual
locations once per second, and we have resampled the data to a resolution of one location per five seconds, in order to make the
temporal resolution equivalent to the Hadza data. In the moveBank data, there is one individual who has spatial data but has
no corresponding demographic data provided, which is individual 2459. This individual has been dropped from the analyses.
Four other days of GPS data were excluded: the GPS data of individual 2452 on 14 August 2012 were excluded because the GPS
readings were clearly in error, and the device only recorded locations for 9.5 h that day, while all other individuals had their
locations recorded for 11.9 h. The locations of individual 2432 on 5 August 2012 were excluded because this track only recorded
for 1.55 h. The locations of individual 2450 on 5 August 2012 were excluded because they only recorded positions for 4.57 h; the
locations of individual 2433 on 6 August 2012 were excluded because they only recorded 7.1 h of data.
(c) Inter-individual proximities
We calculated inter-individual proximities every 5 s on each day, for every possible dyad of individuals. Using this large
dataset, we then made simple calculations of the mean, median and standard deviation in proximity across all times and dyads,
within each study location. Data from each study location were then stratified by hour (e.g. hour 7 covers 7:00:00 until 7:59:59)
and quantiles of dyad distances were calculated for each hour.
(d) Dyadic measure of landscape visitation
The landscape visited by each individual on each day (Li,d) was calculated from the GPS data using the function rasterize in
the R package raster [50]. Using these raster representations, we then measured the similarity and difference in landscape areas
visited each day for each dyad. For this calculation, each 10 m2 raster cell in the landscape was analysed for each day and for
each dyad (i, j) and placed into one of four sets:
— a) Visited by neither i nor j.
— b) Visited only by i
— c) Visited only by j
— d) Visited by both i and j.
Figure 7. Co-authors BP and MA collecting GPS data using lightweight Canmore GPS devices.
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Counts of the raster cells in each of these sets were made (na, nb, nc, nd), and a count of all cells visited by any member of the
dyad (ne = nb + nc+ nd). The measure ‘fraction different’ represents the fraction of the visited landscape that was visited by only
one member of the dyad, and is calculated as (nb+nc)/ne. The measure ‘fraction similar’ is calculated as nd/ne and represents the
fraction of the dyad-visited landscape that was visited by both members of the dyad.
(e) Cumulative measures of landscape exploration
For each study community and each day, we assessed the relationship between the number of individuals included in the
analysis and the cumulative size of the landscape visited by that number of considered individuals. Within each day, we
generated a random order of individual IDs that dictated the order by which subjects’ GPS data would be entered into the
analysis. For the first individual considered within a day, all the 10 m2 raster cells intersected by this individuals’ path of travel
are included in the cumulative metric of total landscape visitation. For the second individual, we carried out a union of the first
and second individuals' rasters of land visitation and then summed the number of raster cells in that union. We continued this
process for each day until all the paths of travel for all individuals had been entered into the cumulative sum.
(f) Sex differences in landscape use
For the Mpala baboon data, we identified all the 10 m2 raster cells intersected by all male tracks and all the cells intersected by
all the female tracks. Set operations were then used to calculate the amount of visited landscape that was visited only by males,
only by females or by both males and females. The same analyses were carried out for 12 different Hadza camps and the results
across these samples averaged [33, table 1].
Ethics. Before participating in the study, all participants were informed about the research and gave their consent. This research received
authorization from the Institutional Review Boards at Harvard University, Yale University, Hunter College, the University of Arizona, and the
University of California, Los Angeles, as well as from the Tanzania Commission for Science and Technology and the National Institute for
Medical Research in Tanzania.
Data accessibility. All the code and data needed to reproduce the text-reported results and figures are available at the Open Science Foundation [51].
Declaration of AI use. B.M.W. used chatGPT 4.0 while devising some of the boiler-plate code used for making figures 1–3. He continued to refine the
code after receiving the initial suggestions.
Authors’ contributions. B.M.W.: conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, project
administration, resources, software, supervision, visualization, writing—original draft, writing—review and editing; D.A.R.: funding
acquisition, investigation, writing—review and editing; H.P.: funding acquisition, investigation, writing—review and editing; J.A.H.:
investigation, writing—review and editing; M.K.S.: investigation, writing—review and editing; B.P.: investigation; M.A.: investigation; A.Z.P.M.:
project administration, supervision.
All authors gave final approval for publication and agreed to be held accountable for the work performed therein.
Conflict of interest declaration. We declare we have no competing interests.
Funding. This work was funding by the US National Science Foundation (grant nos 1062879, 1440671, 2200221), the Leakey Foundation, the
National Geographic Society, and the Max Planck Institute for Evolutionary Anthropology.
Acknowledgements. We thank the Hadza community for their hospitality and support, D. Peterson, T. Peterson, C. Schmelling, N. Dowling and C.
Wood. We thank A. Strandburg-Peshkin, D. Farine, I. Couzin, and M. Crofoot for collecting and sharing the Mpala Olive Baboon data.
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