Elevated rates of horizontal gene transfer in the industrialized human microbiome.

Industrialization has impacted the human gut ecosystem, resulting in altered microbiome composition and diversity. Whether bacterial genomes may also adapt to the industrialization of their host populations remains largely unexplored. Here, we investigate the extent to which the rates and targets of horizontal gene transfer (HGT) vary across thousands of bacterial strains from 15 human populations spanning a range of industrialization. We show that HGTs have accumulated in the microbiome over recent host generations and that HGT occurs at high frequency within individuals. Comparison across human populations reveals that industrialized lifestyles are associated with higher HGT rates and that the functions of HGTs are related to the level of host industrialization. Our results suggest that gut bacteria continuously acquire new functionality based on host lifestyle and that high rates of HGT may be a recent development in human history linked to industrialization.

Reconstructing Prehistoric African Population Structure.

We assembled genome-wide data from 16 prehistoric Africans. We show that the anciently divergent lineage that comprises the primary ancestry of the southern African San had a wider distribution in the past, contributing approximately two-thirds of the ancestry of Malawi hunter-gatherers ∼8,100-2,500 years ago and approximately one-third of the ancestry of Tanzanian hunter-gatherers ∼1,400 years ago. We document how the spread of farmers from western Africa involved complete replacement of local hunter-gatherers in some regions, and we track the spread of herders by showing that the population of a ∼3,100-year-old pastoralist from Tanzania contributed ancestry to people from northeastern to southern Africa, including a ∼1,200-year-old southern African pastoralist. The deepest diversifications of African lineages were complex, involving either repeated gene flow among geographically disparate groups or a lineage more deeply diverging than that of the San contributing more to some western African populations than to others. We finally leverage ancient genomes to document episodes of natural selection in southern African populations. PAPERCLIP.

Entwined African and Asian genetic roots of medieval peoples of the Swahili coast.

The urban peoples of the Swahili coast traded across eastern Africa and the Indian Ocean and were among the first practitioners of Islam among sub-Saharan people1,2. The extent to which these early interactions between Africans and non-Africans were accompanied by genetic exchange remains unknown. Here we report ancient DNA data for 80 individuals from 6 medieval and early modern (AD 1250-1800) coastal towns and an inland town after AD 1650. More than half of the DNA of many of the individuals from coastal towns originates from primarily female ancestors from Africa, with a large proportion-and occasionally more than half-of the DNA coming from Asian ancestors. The Asian ancestry includes components associated with Persia and India, with 80-90% of the Asian DNA originating from Persian men. Peoples of African and Asian origins began to mix by about AD 1000, coinciding with the large-scale adoption of Islam. Before about AD 1500, the Southwest Asian ancestry was mainly Persian-related, consistent with the narrative of the Kilwa Chronicle, the oldest history told by people of the Swahili coast3. After this time, the sources of DNA became increasingly Arabian, consistent with evidence of growing interactions with southern Arabia4. Subsequent interactions with Asian and African people further changed the ancestry of present-day people of the Swahili coast in relation to the medieval individuals whose DNA we sequenced.

Ancient DNA and deep population structure in sub-Saharan African foragers.

Multiple lines of genetic and archaeological evidence suggest that there were major demographic changes in the terminal Late Pleistocene epoch and early Holocene epoch of sub-Saharan Africa1-4. Inferences about this period are challenging to make because demographic shifts in the past 5,000 years have obscured the structures of more ancient populations3,5. Here we present genome-wide ancient DNA data for six individuals from eastern and south-central Africa spanning the past approximately 18,000 years (doubling the time depth of sub-Saharan African ancient DNA), increase the data quality for 15 previously published ancient individuals and analyse these alongside data from 13 other published ancient individuals. The ancestry of the individuals in our study area can be modelled as a geographically structured mixture of three highly divergent source populations, probably reflecting Pleistocene interactions around 80-20 thousand years ago, including deeply diverged eastern and southern African lineages, plus a previously unappreciated ubiquitous distribution of ancestry that occurs in highest proportion today in central African rainforest hunter-gatherers. Once established, this structure remained highly stable, with limited long-range gene flow. These results provide a new line of genetic evidence in support of hypotheses that have emerged from archaeological analyses but remain contested, suggesting increasing regionalization at the end of the Pleistocene epoch.

Biomechanical and taxonomic diversity in the Early Pleistocene in East Africa: Structural analysis of a recently discovered femur shaft from Olduvai Gorge (bed I).

Recent Plio-Pleistocene hominin findings have revealed the complexity of human evolutionary history and the difficulties involved in its interpretation. Moreover, the study of hominin long bone remains is particularly problematic, since it commonly depends on the analysis of fragmentary skeletal elements that in many cases are merely represented by small diaphyseal portions and appear in an isolated fashion in the fossil record. Nevertheless, the study of the postcranial skeleton is particularly important to ascertain locomotor patterns. Here we report on the discovery of a robust hominin femoral fragment (OH 84) at the site of Amin Mturi Korongo dated to 1.84 Ma (Olduvai Bed I). External anatomy and internal bone structure of OH 84 were analyzed and compared with previously published data for modern humans and chimpanzees, as well as for Australopithecus, Paranthropus and Homo specimens ranging from the Late Pliocene to Late Pleistocene. Biomechanical analyses based on transverse cross-sections and the comparison of OH 84 with another robust Olduvai specimen (OH 80) suggest that OH 84 might be tentatively allocated to Paranthropus boisei. More importantly, the identification of a unique combination of traits in OH 84 could indicate both terrestrial bipedalism and an arboreal component in the locomotor repertoire of this individual. If interpreted correctly, OH 84 could thus add to the already mounting evidence of substantial locomotor diversity among Early Pleistocene hominins. Likewise, our results also highlight the difficulties in accurately interpreting the link between form and function in the human fossil record based on fragmentary remains, and ultimately in distinguishing between coeval hominin groups due to the heterogeneous pattern of inter- and intraspecific morphological variability detected among fossil femora.

Perception of strength, attractiveness and aggressiveness of Maasai male faces calibrated to handgrip strength: Evidence from a European sample.

OBJECTIVES: Previous research showed that male and female members of the Maasai from Northern Tanzania judge images of facial morphs calibrated to greater handgrip strength (HGS) higher on strength and attractiveness, but lower on aggressiveness than those calibrated to lower HGS. The accurate assessment of male physical strength from facial information may be adaptive as suggested by the evidence on health and fitness-related benefits linked to high muscular strength. METHODS: This study extends previous work by obtaining European female (n = 220) and male (n = 51) assessments of HGS-calibrated Maasai male faces. Participants rated five facial morphs for strength, attractiveness, and aggressiveness on computer screens. RESULTS: Perceived physical strength increased with morphs calibrated to higher HGS. The lowest and highest HGS morphs were judged lower in attractiveness than the others, and rated aggressiveness decreased in morphs calibrated to higher HGS. CONCLUSIONS: Given the high similarity between the current study findings and those previously reported from intra-population assessments of Maasai faces calibrated to HGS, we suggest that strength and aggressiveness perceptions of facial features associated with male physical strength may be universal. Attractiveness assessments of strength-related information in the faces of (very) strong men were less consistent across populations, possibly attributable to cultural and ecological contexts.

Sitting, squatting, and the evolutionary biology of human inactivity.

Recent work suggests human physiology is not well adapted to prolonged periods of inactivity, with time spent sitting increasing cardiovascular disease and mortality risk. Health risks from sitting are generally linked with reduced levels of muscle contractions in chair-sitting postures and associated reductions in muscle metabolism. These inactivity-associated health risks are somewhat paradoxical, since evolutionary pressures tend to favor energy-minimizing strategies, including rest. Here, we examined inactivity in a hunter-gatherer population (the Hadza of Tanzania) to understand how sedentary behaviors occur in a nonindustrial economic context more typical of humans' evolutionary history. We tested the hypothesis that nonambulatory rest in hunter-gatherers involves increased muscle activity that is different from chair-sitting sedentary postures used in industrialized populations. Using a combination of objectively measured inactivity from thigh-worn accelerometers, observational data, and electromygraphic data, we show that hunter-gatherers have high levels of total nonambulatory time (mean ± SD = 9.90 ± 2.36 h/d), similar to those found in industrialized populations. However, nonambulatory time in Hadza adults often occurs in postures like squatting, and we show that these "active rest" postures require higher levels of lower limb muscle activity than chair sitting. Based on our results, we introduce the Inactivity Mismatch Hypothesis and propose that human physiology is likely adapted to more consistently active muscles derived from both physical activity and from nonambulatory postures with higher levels of muscle contraction. Interventions built on this model may help reduce the negative health impacts of inactivity in industrialized populations.

Microbial biomarkers reveal a hydrothermally active landscape at Olduvai Gorge at the dawn of the Acheulean, 1.7 Ma.

Landscape-scale reconstructions of ancient environments within the cradle of humanity may reveal insights into the relationship between early hominins and the changing resources around them. Many studies of Olduvai Gorge during Pliocene-Pleistocene times have revealed the presence of precession-driven wet-dry cycles atop a general aridification trend, though may underestimate the impact of local-scale conditions on early hominins, who likely experienced a varied and more dynamic landscape. Fossil lipid biomarkers from ancient plants and microbes encode information about their surroundings via their molecular structures and composition, and thus can shed light on past environments. Here, we employ fossil lipid biomarkers to study the paleolandscape at Olduvai Gorge at the emergence of the Acheulean technology, 1.7 Ma, through the Lower Augitic Sandstones layer. In the context of the expansion of savanna grasslands, our results represent a resource-rich mosaic ecosystem populated by groundwater-fed rivers, aquatic plants, angiosperm shrublands, and edible plants. Evidence of a geothermally active landscape is reported via an unusual biomarker distribution consistent with the presence of hydrothermal features seen today at Yellowstone National Park. The study of hydrothermalism in ancient settings and its impact on hominin evolution has not been addressed before, although the association of thermal springs in the proximity of archaeological sites documented here can also be found at other localities. The hydrothermal features and resources present at Olduvai Gorge may have allowed early hominins to thermally process edible plants and meat, supporting the possibility of a prefire stage of human evolution.

Molecular and isotopic evidence for milk, meat, and plants in prehistoric eastern African herder food systems.

The development of pastoralism transformed human diets and societies in grasslands worldwide. The long-term success of cattle herding in Africa has been sustained by dynamic food systems, consumption of a broad range of primary and secondary livestock products, and the evolution of lactase persistence (LP), which allows digestion of lactose into adulthood and enables the milk-based, high-protein, low-calorie diets characteristic of contemporary pastoralists. Despite the presence of multiple alleles associated with LP in ancient and present-day eastern African populations, the contexts for selection for LP and the long-term development of pastoralist foodways in this region remain unclear. Pastoral Neolithic (c 5000 to 1200 BP) faunas indicate that herders relied on cattle, sheep, and goats and some hunting, but direct information on milk consumption, plant use, and broader culinary patterns is rare. Combined chemical and isotopic analysis of ceramic sherds (n = 125) from Pastoral Neolithic archaeological contexts in Kenya and Tanzania, using compound-specific δ13C and Δ13C values of the major fatty acids, provides chemical evidence for milk, meat, and plant processing by ancient herding societies in eastern Africa. These data provide the earliest direct evidence for milk product consumption and reveal a history of reliance on animal products and other nutrients, likely extracted through soups or stews, and plant foods. They document a 5,000-y temporal framework for eastern Africa pastoralist cuisines and cultural contexts for selection for alleles distinctive of LP in eastern Africa.

Human burials at the Kisese II rockshelter, Tanzania.

OBJECTIVES: The Late Pleistocene and early Holocene in eastern Africa are associated with complex evolutionary and demographic processes that contributed to the population variability observed in the region today. However, there are relatively few human skeletal remains from this time period. Here we describe six individuals from the Kisese II rockshelter in Tanzania that were excavated in 1956, present a radiocarbon date for one of the individuals, and compare craniodental morphological diversity among eastern African populations. MATERIALS AND METHODS: This study used standard biometric analyses to assess the age, sex, and stature of the Kisese II individuals. Eastern African craniodental morphological variation was assessed using measures of dental size and a subset of Howells' cranial measurements for the Kisese II individuals as well as early Holocene, early pastoralist, Pastoral Neolithic, and modern African individuals. RESULTS: Our results suggest a minimum of six individuals from the Kisese II collections with two adults and four juveniles. While the dating for most of the burials is uncertain, one individual is directly radiocarbon dated to ~7.1 ka indicating that at least one burial is early Holocene in age. Craniodental metric comparisons indicate that the Kisese II individuals extend the amount of human morphological diversity among Holocene eastern Africans. CONCLUSIONS: Our findings contribute to a growing body of evidence that Late Pleistocene and early Holocene eastern Africans exhibited relatively high amounts of morphological diversity. However, the Kisese II individuals suggest morphological similarity at localized sites potentially supporting increased regionalization during the early Holocene.

Physical activity and time budgets of Hadza forager children: Implications for self-provisioning and the ontogeny of the sexual division of labor.

OBJECTIVES: To determine the effects of age and sex on physical activity and time budgets of Hadza children and juveniles, 5-14 years old, including both in-camp and out-of-camp activities. METHODS: Behavioral data were derived from ~15 000 hourly in-camp scan observations of 76 individuals and 13 out-of-camp focal follows on nine individuals. The data were used to estimate energy expended and percentage of time engaged in a variety of routine activities, including food collection, childcare, making and repairing tools, and household maintenance. RESULTS: Our results suggest that (1) older children spend more time in economic activities; (2) females spend more time engaged in work-related and economic activities in camp, whereas males spend more time engaged in economic activities out of camp; and (3) foraging by both sexes tends to net caloric gains despite being energetically costly. CONCLUSIONS: These results show that, among the Hadza, a sexual division of labor begins to emerge in middle childhood and is well in place by adolescence. Furthermore, foraging tends to provide net caloric gains, suggesting that children are capable of reducing at least some of the energetic burden they place upon their parents or alloparents. The findings are relevant to our understanding of the ways in which young foragers allocate their time, the development of sex-specific behavior patterns, and the capacity of children's work efforts to offset the cost of their own care in a cooperative breeding environment.

Polymorphisms of dopamine receptor genes DRD2 and DRD4 in African populations of Hadza and Datoga differing in the level of culturally permitted aggression.

The key regulator in the control of aggressive behavior is dopamine receptors. Association of variants in these genes with aggression has been shown in modern populations. However, these studies have not been conducted in traditional cultures. The aim of our study was to investigate population features in distributions of allele and genotype frequencies of DRD2 rs1800497, DRD4 120 bp Ins, and DRD4 exon III polymorphisms and their associations with aggressive behavior in the traditional African populations of Hadza and Datoga, which display a contrast in their culturally permitted aggression. Overall, 820 healthy unrelated Hadza and Datoga individuals were studied. Self-rated scores of aggression were collected using Buss and Perry's Aggression Questionnaire. Polymerase chain reaction-Restriction fragment length polymorphism (PCR-RFLP) was used to determine the genotype of each individual. We show that the Hadza and the Datoga differed significantly in allele and genotype frequencies of all studied loci. Our association analysis detected that only ethnicity and sex of individuals significantly influenced their aggression rank, but we failed to identify any associations of DRD2 rs1800497, DRD4 120 bp Ins, or DRD4 exon III polymorphisms with aggression. Thus, our data have no strong evidence to support the involvement of polymorphisms of DRD2 and DRD4 in controlling aggressive behavior.

Chronotype variation drives night-time sentinel-like behaviour in hunter-gatherers.

Sleep is essential for survival, yet it also represents a time of extreme vulnerability to predation, hostile conspecifics and environmental dangers. To reduce the risks of sleeping, the sentinel hypothesis proposes that group-living animals share the task of vigilance during sleep, with some individuals sleeping while others are awake. To investigate sentinel-like behaviour in sleeping humans, we investigated activity patterns at night among Hadza hunter-gatherers of Tanzania. Using actigraphy, we discovered that all subjects were simultaneously scored as asleep for only 18 min in total over 20 days of observation, with a median of eight individuals awake throughout the night-time period; thus, one or more individuals was awake (or in light stages of sleep) during 99.8% of sampled epochs between when the first person went to sleep and the last person awoke. We show that this asynchrony in activity levels is produced by chronotype variation, and that chronotype covaries with age. Thus, asynchronous periods of wakefulness provide an opportunity for vigilance when sleeping in groups. We propose that throughout human evolution, sleeping groups composed of mixed age classes provided a form of vigilance. Chronotype variation and human sleep architecture (including nocturnal awakenings) in modern populations may therefore represent a legacy of natural selection acting in the past to reduce the dangers of sleep.

The evolution of human sleep: Technological and cultural innovation associated with sleep-wake regulation among Hadza hunter-gatherers.

Sleep is necessary for the survival of all mammalian life. In humans, recent investigations have generated critical data on the relationship between sleep and ecology in small-scale societies. Here, we report the technological and social strategies used to alter sleep environments and influence sleep duration and quality among a population of hunter-gatherers, the Hadza of Tanzania. Specifically, we investigated the effects that grass huts, sound levels, and fire had on sleep. We quantitatively compared thermal stress in outdoor environments to that found inside grass hut domiciles to test whether the huts function as thermoregulated microhabitats during the rainy season. Using physiological equivalent temperature (PET), we found that the grass huts provide sleep sites with less overall variation in thermal stress relative to outside baseline environments. We also investigated ambient acoustic measures of nighttime environments and found that sound significantly covaried with sleep-wake activity, with greater sound levels associating with less sleep. Finally, after controlling for ecological variables previously shown to influence sleep in this population, fire was shown to neither facilitate nor discourage sleep expression. Insofar as data among contemporary sub-tropical foragers can inform our understanding of past lifeways, we interpret our findings as suggesting that after the transition to full time terrestriality, it is likely that early Homo would have had novel opportunities to manipulate its environments in ways that could have significantly improved sleep quality. We further conclude that control over sleep environment would have been essential for migration to higher latitudes away from equatorial Africa.

Hadza sleep biology: Evidence for flexible sleep-wake patterns in hunter-gatherers.

OBJECTIVES: Cross-cultural sleep research is critical to deciphering whether modern sleep expression is the product of recent selective pressures, or an example of evolutionary mismatch to ancestral sleep ecology. We worked with the Hadza, an equatorial, hunter-gatherer community in Tanzania, to better understand ancestral sleep patterns and to test hypotheses related to sleep segmentation. METHODS: We used actigraphy to analyze sleep-wake patterns in thirty-three volunteers for a total of 393 days. Linear mixed effects modeling was performed to assess ecological predictors of sleep duration and quality. Additionally, functional linear modeling (FLM) was used to characterize 24-hr time averaged circadian patterns. RESULTS: Compared with post-industrialized western populations, the Hadza were characterized by shorter (6.25 hr), poorer quality sleep (sleep efficiency = 68.9%), yet had stronger circadian rhythms. Sleep duration time was negatively influenced by greater activity, age, light (lux) exposure, and moon phase, and positively influenced by increased day length and mean nighttime temperature. The average daily nap ratio (i.e., the proportion of days where a nap was present) was 0.54 (SE = 0.05), with an average nap duration of 47.5 min (SE = 2.71; n = 139). DISCUSSION: This study showed that circadian rhythms in small-scale foraging populations are more entrained to their ecological environments than Western populations. Additionally, Hadza sleep is characterized as flexible, with a consistent early morning sleep period yet reliance upon opportunistic daytime napping. We propose that plasticity in sleep-wake patterns has been a target of natural selection in human evolution.

Physical activity patterns and biomarkers of cardiovascular disease risk in hunter-gatherers.

OBJECTIVES: Time spent in moderate-to-vigorous physical activity (MVPA) is a strong predictor of cardiovascular health, yet few humans living in industrialized societies meet current recommendations (150 min/week). Researchers have long suggested that human physiological requirements for aerobic exercise reflect an evolutionary shift to a hunting and gathering foraging strategy, and a recent transition to more sedentary lifestyles likely represents a mismatch with our past in terms of physical activity. The goal of this study is to explore this mismatch by characterizing MVPA and cardiovascular health in the Hadza, a modern hunting and gathering population living in Northern Tanzania. METHODS: We measured MVPA using continuous heart rate monitoring in 46 participants recruited from two Hadza camps. As part of a larger survey of health in the Hadza, we measured blood pressure (n = 198) and biomarkers of cardiovascular health (n = 23) including C-reactive protein, cholesterol (Total, HDL, and LDL), and triglycerides. RESULTS: We show that Hadza participants spend large amounts of time in MVPA (134.92 ± 8.6 min/day), and maintain these activity levels across the lifespan. In fact, the Hadza engage in over 14 times as much MVPA as subjects participating in large epidemiological studies in the United States. We found no evidence of risk factors for cardiovascular disease in this population (low prevalence of hypertension across the lifespan, optimal levels for biomarkers of cardiovascular health). CONCLUSIONS: Our results provide evidence that the hunting and gathering foraging strategy involves high levels of MVPA, supporting the evolutionary medicine model for the relationship between MVPA and cardiovascular health.

Evidence of Levy walk foraging patterns in human hunter-gatherers.

When searching for food, many organisms adopt a superdiffusive, scale-free movement pattern called a Lévy walk, which is considered optimal when foraging for heterogeneously located resources with little prior knowledge of distribution patterns [Viswanathan GM, da Luz MGE, Raposo EP, Stanley HE (2011) The Physics of Foraging: An Introduction to Random Searches and Biological Encounters]. Although memory of food locations and higher cognition may limit the benefits of random walk strategies, no studies to date have fully explored search patterns in human foraging. Here, we show that human hunter-gatherers, the Hadza of northern Tanzania, perform Lévy walks in nearly one-half of all foraging bouts. Lévy walks occur when searching for a wide variety of foods from animal prey to underground tubers, suggesting that, even in the most cognitively complex forager on Earth, such patterns are essential to understanding elementary foraging mechanisms. This movement pattern may be fundamental to how humans experience and interact with the world across a wide range of ecological contexts, and it may be adaptive to food distribution patterns on the landscape, which previous studies suggested for organisms with more limited cognition. Additionally, Lévy walks may have become common early in our genus when hunting and gathering arose as a major foraging strategy, playing an important role in the evolution of human mobility.

Energy expenditure and activity among Hadza hunter-gatherers.

OBJECTIVES: Studies of total energy expenditure, (TEE; kcal/day) among traditional populations have challenged current models relating habitual physical activity to daily energy requirements. Here, we examine the relationship between physical activity and TEE among traditional Hadza hunter-gatherers living in northern Tanzania. METHODS: Hadza adults were studied at two camps, with minimal intervention so as to monitor energy expenditure and activity during normal daily life. We measured daily walking distance and walking speed using wearable GPS units for 41 adults. For a subset of 30 adults, we measured TEE using doubly labeled water, three indices of work load (foraging return rate, maternal status, and number of dependent children), and urinary biomarkers of metabolic activity and stress (8-hydroxydeoxyguanosine, cortisol, and testosterone). RESULTS: Fat-free mass was the single strongest predictor of TEE among Hadza adults (r(2) = 0.66, P < 0.001). Hadza men used greater daily walking distances and faster walking speeds compared with that of Hadza women, but neither sex nor any measure of physical activity or work load were correlated with TEE in analyses controlling for fat-free mass. Compared with developed, industrial populations, Hadza adults had similar TEE but elevated levels of metabolic stress as measured by 8-hydroxydeoxyguanosine. CONCLUSION: Our results indicate that daily physical activity may not predict TEE within traditional hunter-gatherer populations like the Hadza. Instead, adults with high levels of habitual physical activity may adapt by reducing energy allocation to other physiological activity.

Honey, Hadza, hunter-gatherers, and human evolution.

Honey is the most energy dense food in nature. It is therefore not surprising that, where it exists, honey is an important food for almost all hunter-gatherers. Here we describe and analyze widespread honey collecting among foragers and show that where it is absent, in arctic and subarctic habitats, honey bees are also rare to absent. Second, we focus on one hunter-gatherer society, the Hadza of Tanzania. Hadza men and women both rank honey as their favorite food. Hadza acquire seven types of honey. Hadza women usually acquire honey that is close to the ground while men often climb tall baobab trees to raid the largest bee hives with stinging bees. Honey accounts for a substantial proportion of the kilocalories in the Hadza diet, especially that of Hadza men. Cross-cultural forager data reveal that in most hunter-gatherers, men acquire more honey than women but often, as with the Hadza, women do acquire some. Virtually all warm-climate foragers consume honey. Our closest living relatives, the great apes, take honey when they can. We suggest that honey has been part of the diet of our ancestors dating back to at least the earliest hominins. The earliest hominins, however, would have surely been less capable of acquiring as much honey as more recent, fully modern human hunter-gatherers. We discuss reasons for thinking our early ancestors would have acquired less honey than foragers ethnographically described, yet still significantly more than our great ape relatives.

Hadza Landscape Burning.

We present the first published ethnographic description of landscape burning by Hadza hunter-gatherers of northern Tanzania and identify environmental, social, and cultural influences on Hadza landscape burning, thereby broadening the ethnographic record of anthropogenic burning practices described for hunter-gatherer communities. We report interview data collected in 2022 and 2023, describing their practices and attitudes regarding the causes and consequences of burning. We provide context by comparing our observations with those recorded for hunting and gathering populations in Africa, Australia, and North America. Hadza landscape burning is generally a solitary and male-dominated activity, contrary to ethnographic accounts of Indigenous landscape burning from North America and Australia. The primary goals stated by Hadza for landscape burning were improved hunting, reduced hazards from dangerous animals, and to reduce the density of livestock. Firsthand observations suggest that landscape burning has decreased over the past 20 years, and this historical trend is supported by interviews. Satellite imagery also suggests an overall decrease in burning activity in the region from 2001 to 2022. Among the Hadza, landscape burning is a culturally influenced and strongly gender-biased activity that is rapidly disappearing. Because burning can radically transform landscapes, these practices often generate or amplify conflicts of interest between groups with different land use strategies. Hadza report serious social conflict with pastoralists over landscape burning, and our study suggests this tension has constrained the practice in the past two decades.