David R Samson

University of Toronto | U of T · Department of Anthropology

Over the past four decades, scientists have made substantial progress in understanding the evolution of sleep patterns across the Tree of Life.[1, 2] Remarkably, the specifics of sleep along the human lineage have been slow to emerge. This is surprising, given our unique mental and behavioral capacity and the importance of sleep for individual cogn...

The daily construction of a sleeping platform or "nest" is a universal behavior among large-bodied hominoids. Among chimpanzees, most populations consistently select particular tree species for nesting, yet the principles that guide species preferences are poorly understood. At Semliki, Cynometra alexandri constitutes only 9.6% of all trees in the...

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 te...

The nightly construction of an arboreal sleeping platform (SP) has been observed among every chimpanzee's population studied to date. Here, we report on bioclimatic aspects of SP site choice among dry-habitat chimpanzees (Pan troglodytes schweinfurthii) at the Toro-Semliki Wildlife Reserve, Uganda. We placed a portable weather monitor within 1 m of...

Of the extant primates, only 20 non-human species have been studied by sleep scientists. Notable sampling gaps exist, including large-bodied hominoids such as gorillas (Gorilla gorilla), orangutans (Pongo spp.) and bonobos (Pan paniscus), for which data have been characterized as high priority. Here, we report the sleep architecture of three female...

The function of dreams is a longstanding scientific research question. Simulation theories of dream function, which are based on the premise that dreams represent evolutionary past selective pressures and fitness improvement through modified states of consciousness, have yet to be tested in cross-cultural populations that include small-scale forage...

Sleep quality is an important contributor to health disparities and affects the physiological function of the immune and endocrine systems, shaping how resources are allocated to life history demands. Past work in industrial and post-industrial societies has shown that lower total sleep time (TST) or more disrupted nighttime sleep are linked to fla...

Evolutionary theories suggest that dreams function as a world simulator of events that maximizes our ability to surmount social and threat-related challenges critical to survivorship and reproduction. Here, in contrast to the incorporation continuity hypothesis, we test the (1) social bias hypothesis, which states that dreams will overrepresent pos...

Background and objectives Sleep is a vulnerable state in which individuals are more susceptible to threat, which may have led to evolved mechanisms for increasing safety. The sentinel hypothesis proposes that brief awakenings during sleep may be a strategy for detecting and responding to environmental threats. Observations of sleep segmentation and...

Sleep duration, quality, and rest-activity pattern—a measure for inferring circadian rhythm—are influenced by multiple factors including access to electricity. Recent findings suggest that the safety and comfort afforded by technology may improve sleep but negatively impact rest-activity stability. According to the circadian entrainment hypothesis,...

Given the contributions of sleep to a range of health outcomes, there is substantial interest in ecological and environmental factors, including psychosocial contexts, that shape variation in sleep between individuals and populations. However, the links between social dynamics and sleep are not well-characterized beyond Euro-American settings, repr...

Social status among group-living mammals can impact access to resources, such as water, food, social support, and mating opportunities, and this differential access to resources can have fitness consequences. Here, we propose that an animal's social status impacts their access to sleep opportunities, as social status may predict when an animal slee...

There are limited studies investigating the combined effects of biological, environmental, and human factors on the activity of the domestic dog. Sled dogs offer a unique opportunity to examine these factors due to their close relationship with handlers and exposure to the outdoors. Here, we used accelerometers to measure the activity of 52 sled do...

Characteristics of the sleep-site are thought to influence the quality and duration of primate sleep, yet only a handful of studies have investigated these links experimentally. Using actigraphy and infrared videography, we quantified sleep in four lemur species (Eulemur coronatus, Lemur catta, Propithecus coquereli, and Varecia rubra) under two di...

The human sleep pattern is paradoxical. Sleep is vital for optimal physical and cognitive performance, yet humans sleep the least of all primates. In addition, consolidated and continuous monophasic sleep is evidently advantageous, yet emerging comparative data sets from small-scale societies show that the phasing of the human pattern of sleep–wake...

Sleep studies in small-scale subsistence societies have broadened our understanding of cross-cultural sleep patterns, revealing the flexibility of human sleep. We examined sleep biology among BaYaka foragers from the Republic of Congo who move between environmentally similar but socio-ecologically distinct locations to access seasonal resources. We...

Characteristics of the sleep-site are thought to influence the quality and duration of primate sleep, yet only a handful of studies have investigated these links experimentally. Using actigraphy and infrared videography, we quantified sleep in four lemur species ( Eulemur coronatus, Lemur catta, Propithecus coquereli, and Varecia rubra ) under two...

Sleep in the primate order remains understudied, with quantitative estimates of sleep duration available for less than 10% of primate species. Even fewer species have had their sleep synchronously quantified with meteorological data, which have been shown to influence sleep-wake regulatory behaviors. We report the first sleep duration estimates in...

The COVID-19 pandemic and its associated stressors have impacted the daily lives and sleeping patterns of many individuals, including university students. Dreams may provide insight into how the mind processes changing realities; dreams not only allow consolidation of new information, but may give the opportunity to creatively “play out” low-risk,...

Objectives To characterize sleep and circadian rhythms of a sample population of healthy, dog-owning adults from North Carolina, USA. Methods Actigraphy was used to analyze sleep-wake patterns in forty-two dog owners from the Raleigh area in North Carolina. Sleep quotas, including sleep duration, efficiency, and fragmentation were measured alongsi...

The study of companion (pet) dogs is an area of great translational potential, as they share a risk for many conditions that afflict humans. Among these are conditions that affect sleep, including chronic pain and cognitive dysfunction. Significant advancements have occurred in the ability to study sleep in dogs, including development of non-invasi...

Objectives Remarkably, the specifics of sleep along the human lineage have been slow to emerge, which is surprising given our distinct mental and behavioral capacity and the importance of sleep for individual health and cognitive performance. Largely due to difficultly of measuring sleep outside a controlled, clinical, and laboratory study in ambul...

Human sleep is linked with nearly every aspect of our health and wellbeing. The question whether and to what extent human sleep is in a state of evolutionary mismatch has gained recent attention from both clinical and biological science researchers. Here, I use a comparative Bayesian approach aimed at testing the sleep epidemic hypothesis – the ide...

Objectives The pooling of energetic resources and food sharing have been widely documented among hunter‐gatherer societies. Much less is known about how the energetic costs of daily activities are distributed across individuals in such groups, including between women and men. Moreover, the metabolic physiological correlates of those activities and...

The pathophysiology of insomnia remains poorly understood, yet emerging cross-disciplinary approaches integrating natural history, observational studies in traditional populations, gene-phenotype expression and experiments, are opening up new avenues to investigate the evolutionary origins of sleep disorders, with the potential to inform innovation...

Sleep is essential for survival, yet it represents a time of extreme vulnerability, including through exposure to parasites and pathogens transmitted by biting insects. To reduce the risks of exposure to vector-borne disease, the encounter-dilution hypothesis proposes that the formation of groups at sleep sites is influenced by a “selfish herd” beh...

The original version of this article unfortunately contained a mistake in the authorgroup section.

In humans, pain due to osteoarthritis has been demonstrated to be associated with insomnia and sleep disturbances that affect perception of pain, productivity, and quality of life. Dogs, which develop spontaneous osteoarthritis and represent an increasingly used model for human osteoarthritis, would be expected to show similar sleep disturbances. F...

Primates spend almost half their lives asleep, yet little is known about how sleep influences their waking cognition. We hypothesized that diurnal and cathemeral lemurs differ in their need for consistent, non-segmented sleep for next-day cognitive function—including long-term memory consolidation, self-control, foraging efficiency, and sociality....

Sleep is a critically important dimension of primate behavior, ecology, and evolution, yet primate sleep is under-studied because current methods of analyzing sleep are expensive, invasive, and time-consuming. In contrast to electroencephalography (EEG) and actigraphy, videography is a cost-effective and non-invasive method to study sleep architect...

Objectives: The lunar cycle is expected to influence sleep-wake patterns in human populations that have greater exposure to the environment, as might be found in forager populations that experience few environmental buffers. We investigated this “moonlight” hypothesis in two African populations: one composed of hunter-gatherers (with minimal enviro...

Objective: Despite widespread interest in maternal–infant co-sleeping, few quantified data on sleep patterns outside of the cultural west exist. Here, we provide the first report on co-sleeping behavior and maternal sleep quality among habitually co-sleeping hunter-gatherers. Design: Data were collected among the Hadza of Tanzania who live in domic...

Elevated blood pressure presents a global health threat, with rates of hypertension increasing in low and middle-income countries. Lifestyle changes may be an important driver of these increases in blood pressure. Hypertension is particularly prevalent in African countries, though the majority of studies have focused on mainland Africa. We collecte...

Demographic data, as related to lifestyle and household attributes. (PDF)

Comparison of the first and third blood pressure readings from 2016 and 2017. The third measurement is lower than the first. (EPS)

Cohort demographics, where SBP and DBP are the third readings. (PDF)

Predictors of blood pressure, as related to lifestyle and household attributes, from 2015 data (N = 47). (PDF)

SBP (R2 = 0.186, p<0.001) and DBP (R2 = 0.067, p<0.001) increases with age. The dashed line indicates the minimum blood pressure value for hypertension. (PDF)

Objectives Primates spend almost half their lives asleep, yet we know little about how evolution has shaped variation in the duration or intensity of sleep (i.e., sleep regulation) across primate species. Our objective was to test hypotheses related to how sleeping site security influences sleep intensity in different lemur species. Methods We use...

Objectives: Primates vary in their sleep durations and, remarkably, humans sleep the least per 24-hr period of the 30 primates that have been studied. Using phylogenetic methods that quantitatively situate human phenotypes within a broader primate comparative context, we investigated the evolution of human sleep architecture, focusing on: total sl...

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 hunte...

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 investig...

Global and evolutionary perspectives on sleep Sleep Health Request for Papers (RFP) 2017-2018 Guest editors: David R. Samson & Gandhi M. Yetish Modernization has rapidly transformed sleep environments worldwide. This transformation has been marked by the expansion of artificial lighting, screen-based digital media, and controlled, temperature-cons...

Cathemerality, or activity throughout the 24-hr cycle, is rare in primates yet relatively common among lemurs. However, the diverse ecological conditions under which cathemerality is expressed complicates attempts to identify species-typical behavior. For example, Lemur catta and Varecia have historically been described as diurnal, yet recent studi...

Objectives: We studied sleep in a rural population in Madagascar to (i) characterize sleep in an equatorial small-scale agricultural population without electricity, (ii) assess whether sleep is linked to noise levels in a dense population, and (iii) examine the effects of experimentally introduced artificial light on sleep timing. Methods: Using...

Objective: To compare different scoring parameter settings in actigraphy software for inferring sleep and wake bouts for validating analytical techniques outside of laboratory environments. Design: To identify parameter settings that best identify napping during periods of wakefulness, we analyzed 137 days on which participants reported daytime...

Sleep is essential to cognitive function and health in humans, yet the ultimate reasons for sleep - i.e., why sleep evolved - remain mysterious. We integrate findings from human sleep studies, the ethnographic record, and the ecology and evolution of mammalian sleep to better understand sleep along the human lineage and in the modern world. Compare...

The nightly construction of arboreal sleeping platforms or "nests" has been observed among every great ape population studied to date. However, this behavior has never been reported in any other nonhuman primate and comparisons between ape and monkey sleep illuminate the link between sleeping substrates, positional behavior, and sleep efficiency. H...

The nightly construction of a 'nest' or sleeping platform is a behavior that has been observed in every wild great ape population studied, yet in captivity, few analyses have been performed on sleep related behavior. Here, we report on such behavior in three female and two male captive orangutans (Pongo spp.), in a natural light setting, at the Ind...

Researchers have suggested that the ability of male primates to emit long-distance vocalizations is energetically costly and potentially incurring important adaptive consequences upon the calling individuals. Here, we present the first preliminary data on captive orangutan (Pongo spp.) nocturnal long calls, generated at the Indianapolis Zoo. We use...

The great apes, humans included, are unique in that they share the universal trait of sleeping platform building. Even primates characterized by large body and brain mass (e.g., Papio and Mandrillus) and/or high levels of intelligence (e.g., Cebus) do not build nightly platforms on which to sleep. Therefore, a direct comparison between a large-bodi...

It has been hypothesized that with the advent of the Miocene, apes began to manufacture complex sleeping platforms to create more comfortable and stable sleeping environments which resulted in a lengthening of sleep architecture and augmented cognition. The cognitive effects of quality sleep in large bodied hominoids have yet to be tested. We hypot...

Great apes spend half of their lives in a nightly "nest" or sleeping platform (SP), a complex object created by modifying foliage, which functions as a stable substrate on which to sleep. Of the several purported functions of SPs, one hypothesis is that they protect against parasitic infection. Here we investigate the role of SP site choice in avoi...

The nightly construction of a sleeping platform (SP) or "nest" is widely regarded as a universal behavior among great apes, yet SP structural morphology has been incompletely quantified to date. This is in part due to the inherent difficulties of gathering empirical data on arboreally sited SPs. I gathered quantitative structural data on SPs (n = 6...

From the works of Broca and Krogman to modern-day Jantz and Buikstra, the orbit has been used for both quantitative and qualitative sex and race estimation. This study evaluates the practical value of these estimations. Orbital height and breadth were measured to determine the orbital index and assess differences between men and women or black peop...

The function of the Acheulean handaxe is controversial. Several competing usage theories are currently being debated amongst paleoanthropologists. One such hypothesis is the lethal projectile theory. Past experimentation has indicated that the handaxe could have been used as a lethal projectile thrown from a distance to hunt prey. This actualistic...