The Sweaty Origins of Human Thermal Resilience
Sedentism, the practice of settling in a place over extended periods of time, has had a long history in some parts of the world as one concurrent with agricultural intensification, food domestication, and sociopolitical development.1 Earlier theories of sedentism frame it as a driver, even prerequisite for chronological progress from simple hunter-gatherer subsistence to more complex social systems.2 Yet, over the past four decades, archeological studies across prehistoric sites have challenged this myth, framing the complex evolution of sedentism as a habitation pattern initially driven by changes in climate, and maintained by technological innovation and labor hierarchies.3
After humans spread from the African continent, recent studies on their foraging patterns in Asia and the tropical Americas have revealed the importance of transitory periods of oscillation between tropical forest biomes and open, arid grassland savannahs. Such movements from one bioclimatic context to another were long, drawn-out processes where a mixture of mobile and sedentary practices occurred simultaneously. During these early transitory periods to sedentary settlements, humans developed physiological capacities around thermal comfort and survival that supported such movement between these two environments.4 Whereas in the pre-Holocene environment, the human body was largely surrounded by trees and shaded from the sun in the mixed humid forests of tropical biomes, open grassland environments and the eventual exploitation of forest resources presented them with an overwhelming, stressful environmental challenge: the direct glare of the sun.
As the body enters warmer environments and engages the direct glare of the sun, human blood vessels expand to as much as ten times in width in order to transport heat to the skin’s surface where it is expelled mainly through the evaporation of sweat.5 Compared to human respiration, where the body expels 40 grams of moisture and roughly 28 watts of heat every hour, sweat glands can produce up to 2 to 3 liters of water per hour, expelling 675–700 watts of heat from the skin’s surface.6 Maintained by constant blood flow and sweat secretion, this dissipation of heat maintains the human body’s surface temperature under 40 degrees Celsius, and core temperature around 37 degrees Celsius.7
With over two million eccrine glands lying beneath the skin’s dermis layer, the human capacity to rapidly diffuse heat from the body surpasses that of most mammals.8 While other mammals sweat through localized or significantly fewer apocrine glands that secrete thick, protein-rich fluids primarily in response to stress, humans leverage the evaporation of water from this distributed network to effectively thermoregulate. Given the evaporation of 1 liter of sweat rids the body of approximately 700 watts of energy per hour, the sweating human performs cooling work comparable to that of a small window air-conditioning unit.9 Existing hypotheses attribute this super-cooling capacity to part of a vital adaptation strategy, allowing humans to hunt and explore during the hottest parts of the day when predatory mammals were hiding from the sun.10
Apart from water, the release of fractional percentages of salts, urea, heavy metals, electrolytes, fats, metabolites, and volatile compounds in human sweat during exercise has long been understood as symptoms of human circulatory, lymphatic, and immune system health.11 Historically used as visual and olfactory evidence of the underlying emotional, metabolic, and health states of the human body, sensing sweat was essentially used as a form of social communication.12 Today, sweat is a dirty word in a world of comfort, evoking a broad spectrum of largely negative emotional states, like stress, panic, fear, and shame. The social stigmatization of sweat has become closely associated with indicators of health, hygiene, and socioeconomic class.13 Even in the context of exercise, during which the human body produces between one to three liters of sweat, its visual and olfactory presence is often masked and quickly eliminated through a broad range of strategies: antiperspirants, deodorants, sweat-absorbing fabrics, sweat-repelling towels, fans, air fresheners, air conditioning, and cooling technologies. This chemical and technological landscape designed to prevent sweat has socialized a complex aspirational culture of comfort continuously reinforced by a culture of increasing indoor lifestyles and sedentism.
Comfort Sickness: Costs of the Sweatless Interior
The sedentary human body has played a central role in the historical development of modern thermal comfort. Early thermal comfort research in the 1910s by industrial engineers, physiologists, and academics in the United States and Europe sought to define human comfort across a growing range of built environments, from indoor industrial factories to ventilated civic buildings in colonized contexts. Over the next few decades, experiments conducted in “climate chambers,” where key environmental variables could be acutely controlled, allowed researchers to develop a quantitative framework for defining indoor human comfort.14 However, in doing so, researchers focused primarily on controlling indoor air temperature and humidity, and largely ignored the impacts of air movement and human activity—two critical environmental and human precursors for healthy sweating.15 In the 1960s, the first ASHRAE-55 (American Society of Heating, Refrigerating and Air-Conditioning Engineers) thermal comfort standard was optimized for thermal neutrality, reducing or eliminating sweating by keeping the sedentary body’s average skin temperature at 34 degrees Celsius through the recommended use of air conditioning.16
It was not until the 1980s that seminal studies began to look at the impacts of airflow through occupant-controlled mechanical fans and elevated temperatures characteristic of hot-arid and hot-humid environments. As a result, thermal comfort researchers advocated for new allowable air flow limits in summer periods.17 A decade later, spearheaded by Richard de Dear and Gail Brager, researchers embarked on a large-scale project consisting of field studies in office buildings across diverse climates. While air velocity was not the primary variable in these studies, it was accounted for in the way occupants in naturally-ventilated buildings used fans or opened windows to expand comfort at a broader range of temperatures.18 For buildings designed to promote airflow, de Dear and Brager’s project advocated for establishing a direct relationship between indoor operative temperature and a broader set of historical and real-time contextual adaptations that modify an individual’s preference and expectations. Resulting in “The Adaptive Standard,” this alternative model of thermal comfort allowed for an understanding of how human occupants experience comfort in dynamic, non-steady-state thermal environments through physiological and behavioral regulatory mechanisms.19 Albeit limited, by accounting for the human’s experience of outdoor temperatures and their active use of airflow devices, such studies opened the door for human thermal agency to be reflected in ASHRAE comfort standards.20
Sixty years after the first comfort standards were established, emergent patterns of indoor occupation have substantially reduced daily human movement and outdoor activity. Despite the incrementally expanding understanding of diverse human adaptive thermal capacities, environmental control technologies have shaped new, reinforcing cultures of interiority. With humans spending over 90 percent of their time indoors, attendant shifts in sedentary lifestyles have driven an epidemic of cardiovascular disease and obesity.21 Spared from heat exposure and movement in outdoor air conditions, the human body in thermoneutral environments has demonstrated declining resilience patterns across human populations. In adult men, reduced exposure to cold environments has been correlated to reduction of brown adipose tissue responsible for weight and body fat regulation.22 For children who also spend 90 percent of time indoors, opportunities to repeatedly activate sweating during the early years of growth limits their acclimatization to local outdoor climates, alongside the development of immune system resilience and cardiorespiratory endurance.23
Continuous indoor occupancy has also driven high building energy demands and associated operational costs. Contemporary mechanical heating, ventilation, and air conditioning (HVAC) systems account for over half of buildings’ energy consumption. In addition to cooling air, a significant amount of energy spent is on removing moisture from building air streams depending on the climate.24 Qualitatively, the impact of this mechanical processing of high moisture loads has led to highly pathogenic interior air streams, leading to widespread acute and chronic respiratory illness as well as sick building syndrome.25 And with shifting American national standards requiring higher ventilation rates to compensate for poor indoor air quality, moisture—which already forms up to 87 percent of ventilation loads—will drive even higher energy consumption rates by HVAC systems.
Sweaty Skins: Towards Architectures of Acclimatization
In as much as the prevention of sweat has been the subject of environmental control technologies since the 1960s, a parallel shift has taken place in prevailing trends of modern architecture from hygrothermally active building envelopes to sealed, mineral based systems.26 Across varied climatic contexts throughout the world, exterior hygroscopic building technologies like green roofs, earthen thermal mass, or biomass roof assemblies typically relied on diurnal swings in outdoor climates to condition indoor spaces. From the thick adobe walls of stepped Pueblo houses in the arid desert climate of the Southwestern United States to the porous, plant-fiber walls of the tropical kampung architecture across Southeast Asia, humans have historically wrapped themselves and their houses with multitudes of sweaty soil, plant, and animal materials to defend against climatic forces. While passive hygrothermally active strategies are comparatively slow and climate-dependent relative to mechanical conditioning systems, designing with the hygrothermal performance of porous materials can offer dual passive cooling capacities in buildings: sorbing significant amounts of moisture from humid outdoor air at certain times of the day and evaporating during the following day to provide a range of cooling effects.27 Through the proper sizing of wall thickness, density, and effective integration, hygrothermally active building envelopes can significantly drive down a building’s operational energy over time.
For example, in the last decade, renewed studies on exterior fiberboards developed from coconut agricultural wastes have shown great potential for intrinsic evaporative cooling and indoor humidity control in contemporary tropical buildings. Studies demonstrate hygrothermally active coconut fiberboards effectively diminishing moisture building loads from humid air, and driving an average daytime evaporative cooling effect of approximately 50 watts per square meter for walls and 15 watts per square meter for roof surfaces.28 With substantially reduced humidity loads, a combination of natural ventilation, shading, and lower-energy mechanical technologies can be used to address high temperatures.
Extending this to the building material’s whole life cycle, celebrating porosity as a desirable component of building-material performance not only reopens up the participation of a broad range of low-carbon biomass streams to engage in thermal adaptability, but enables probiotic material circularity. Contemporary approaches that extend the durability or fire performance of contemporary building products by pumping material products with synthetic glues and additives often leads to high embodied carbon footprints and enduring legacy of toxicity across material life cycles.29 In opposition to such “material botox” approaches that prioritize mechanical strength and moisture resistance over porosity, breathable materials ensure the non-toxic reuse, recycling, and ultimately healthy degradation of materials.30
Built for Sweat: Cultures of Inhabiting Heat
From Indigenous Mesoamerican Indian temazcals (sweat lodges) and hammams to Eskimo steam baths, social rituals of sweating have been linked to improved acclimatization and health. Regularized practices induce a range of physiological adaptations in resting core body temperature, heart rate, sweat rate, and blood flow, effectively improving the thermoregulatory efficiency of the human body. Coupled with practices of detoxification, healing, and cleansing, socialization within sweating rituals trains the young to withstand and normalize thermal stress, shaping the mind’s relationship to thermal discomfort. In cultures where sweating practices are habitual, repeated human exposure to contrasting thermal environments also allows for spatial and temporal thermal alliesthesia—how a person may experience pleasure based on their thermal state and the environments they experience.31
When community life became condensed in the subarctic polar during winter months, a diverse range of Eskimo cultures practiced sweat baths daily in indoor qasgiqs. Qasgiqs were semi-subterranean structures primarily occupied by men where celebratory communal events, training, and religious rituals took place.32 From a central pit, direct heat supplied from burning wood was used to heat an entire room. Using smoke holes and a hole in the well-insulated sod roof, indoor heat was controlled to reach temperatures of about 255 degrees Fahrenheit. Following a round of sweating, men would wash themselves outside with cold water or snow where temperatures were typically well below 25 degrees Fahrenheit.33 Over rounds of sweating, participants developed a cultural tolerance of extreme heat and cold.34
Similarly, in hot-arid climates, hammams have long been carefully designed to socialize sweating. Stemming from the Arabic word “al-Hamma,” meaning hot spring, the hammam bathhouse employs a range of strategies to engage the human body’s psychological capacity to withstand thermal changes comfortably.35 Ancient Persian medical and religious texts and encyclopedias dating back to the tenth century refer to sweating induced by herbs as well as a range of hot and dry bathing conditions.36 From an open entrance space where visitors change into absorbent towels or wrap materials, the tempered progression from a moderately hot space (68 to 86 degrees Fahrenheit) provides an opportunity for heat preexposure adjustments before entering the core sauna where temperatures reach 100 to 120 degrees Fahrenheit. After exposure in the sauna, the use of a buffer room typically integrating a cold-water feature provides an opportunity to rinse and decrease metabolic rates. The final phase includes a resting, socializing space where water and tea is typically offered to bathers.
Exploring the hammam as a rich sensorium, the anthropologist Julie Peteet frames the acoustic, olfactory, lighting, tactile, and tasting components of the bathhouse typology as an intersensorial approach to human thermal regulation.37 As one progresses through the hammam, human senses are heightened and soothed through culturally mediated “synesthesia”—sensory intermingling over time.38 For example, the distinct smell of “heat,” or the recognizable “musky odors” formed from the interaction of stone, oils, sweat, and soap, can over time trigger familiarity and relaxation. Viewed in this light, the heated spaces in the hammam are not merely tolerable but in some cases evolve to become pleasurable as one moves through them.
Given that the regular activation of the human sweat glands improve over time—reducing sweating rates by 50–60 percent or from 2 to 3 liters to under 1 liter per hour—revitalizing sweating may offer an important frontier for practicing and overcoming human discomfort. Learning from qasgiq and hammam cultures, heat-therapy practices offer different models for conditioning the human body and mind in an era of climate extremes. In extremely cold climates where heat conservation is the utmost priority, the daily practice of oscillating between an extremely hot room and the cold outside enables the human body to withstand temperature differentials of 280 degrees Fahrenheit. In arid climates, where temperatures fluctuate between 40–50 degrees Fahrenheit between day and night, heat tolerance is cultivated through a relatively gentle progression towards temperatures just above peak daytime temperatures. Similar to our ancestors’ transitions from forest to savannah during the Pleistocene era, longstanding sweating practices remind us that human thermal adaptation is a cultivated relationship between mind, body, and changing environments.
G. K. Dow and C. G. Reed, “The Origins of Sedentism: Climate, Population, and Technology,” Journal of Economic Behavior & Organization 119 (2015): 56–71.
T. Douglas Price, “Social Inequality at the Origins of Agriculture,” in Foundations of Social Inequality (Boston, MA: Springer US, 1995), 129–51. See also R. Lewin, “A Revolution of Ideas in Agricultural Origins,” Science 240, no. 4855 (1988): 984; T.D. Price and J.A. Brown, “Aspects of Hunter-Gatherer Complexity,” in Prehistoric Hunters-Gatherers (Academic Press, 1985), 3–20; Robert L. Kelly, The Lifeways of Hunter-Gatherers: The Foraging Spectrum (Cambridge University Press, 2013).
In particular, climate change during the Holocene period, which led to decreased variance in environmental conditions, has emerged as the most important driver in human habitation shifts, driving the transition from temporary, “mobile foraging” nomadism to permanent “sedentary foraging” settlements.
Eleanor M. Scerri et al., “Tropical Forests in the Deep Human Past,” Philosophical Transactions of the Royal Society B 377, no. 1849 (2022): 2–4.
In hand and feet extremities, blood flow rates can vary by a factor of thirty. B. W. Olesen, “Thermal Comfort,” Technical Review 2 (1982): 30.
Olesen, “Thermal Comfort,” 6–12; S. Robinson and A.H. Robinson, “Chemical Composition of Sweat,” Physiological Reviews 34, no. 2 (1954): 202–03; R. W. Newman, “Why Man is Such a Sweaty and Thirsty Naked Animal: A Speculative Review,” Human Biology 42, no. 1 (1970): 17.
W. Berry Lyons et al., “The Hydrogeochemistry of Shallow Groundwater from Lut Desert, Iran: The Hottest Place on Earth,” Journal of Arid Environments 178 (2020): 1; Paul J. Chestovich et al., “Temperature Profiles of Sunlight-Exposed Surfaces in a Desert Climate: Determining the Risk for Pavement Burns,” Journal of Burn Care & Research 44, no. 2 (2023): 438–45; P.O. Fanger, “Assessment of Man’s Thermal Comfort in Practice,” Occupational and Environmental Medicine 30, no. 4 (1973): 315.
Andrew Best et al., “Diversity and Evolution of Human Eccrine Sweat Gland Density,” Journal of Thermal Biology 84 (2019): 332.
Small window air-conditioners use between 400–700 watts per hour.
Daniel E. Lieberman, “Human Locomotion and Heat Loss: an Evolutionary Perspective,” Comprehensive Physiology 5, no. 1 (2015): 99.
A broad range of human sweating rates and changes in sweat composition are primarily driven by individual temperature thresholds and thermal sensitivity, modified by individual factors such as age, diet, menstrual states, health states, genetic traits, and environmental factors including altitude and microgravity. Lindsay B. Baker, “Physiology of Sweat Gland Function: The Roles of Sweating and Sweat Composition in Human Health,” Temperature 6, no. 3 (2019): 216.
Laura Caitlyn Hatcher, “Chemical Communication: The Effects of Stress-Induced Apocrine Sweat on Human Perceptions and Interactions,” (PhD diss., Louisiana State University and Agricultural & Mechanical College, 2016); Hannah Della Bosca, “Sweat Speaks: Stories of Embodiment, Emotion, and Erasure on a Heating Planet,” Emotion, Space and Society 53 (2024): 101051.
Gordon Waitt and Elyse Stanes, “Sweating Bodies: Men, Masculinities, Affect, Emotion,” Geoforum 59 (2015): 30–38.
Mae-ling Lokko, “Hot Air Rising,” Digestion (e-flux Architecture, September 2022), ➝. See also Olesen, “Thermal Comfort,” 19; Health of Munition Workers Committee, Final Report: Industrial Health and Efficiency (London: HMSO, 1918); G. A. Atkinson, “Building in the Tropics,” Royal Institute of British Architects Journal 57 (1950); G. A. Atkinson, “Warm Climates and Building Design,” Colonial Building Notes 12 (1953).
Indoor air movement was restricted to a maximum of 0.24 m/s to avoid complaints about draft. C.P. Yaglou, “The Comfort Zone for Men at Rest and Stripped to the Waist,” Transactions of the American Society of Heating and Ventilating Engineers 33 (1927): 165–79; F. C. Houghten and C. P. Yaglou, “Determination of the Comfort Zone,” Transactions of the American Society of Heating and Ventilating Engineers 29 (1923); M. Fountain and E. A. Arens, “Air Movement and Thermal Comfort,” ASHRAE Journal 35, no. 8 (1993): 27.
Olesen, “Thermal Comfort,” 6.
Apart from initial increases in the 1970s and 80s to account for summer conditions, which increased air velocities to 0.36 and 0.25 m/s respectively, air movement limits in the ASHRAE-55 comfort standard remained a conservative 0.15 m/s into the 1990s. F. H. Rohles et al., “Ceiling Fans Extenders of the Summer Comfort Envelope,” ASHRAE Transactions 89 (1983): 245–63; D. G. Scheatzle et al., “Extending the Summer Comfort Envelope with Ceiling Fans in Hot, Arid Climates,” ASHRAE Transactions 95 (1989): 269–80; S. Tanabe and K. Kimura, “Thermal Comfort Requirements Under Hot and Humid Conditions,” Proceeding of ASHRAE Far East Conference, Singapore (September 1987): 3–21.
Tanabe and Kimura, “Thermal Comfort Requirements Under Hot and Humid Conditions,” 6. See also Yaglou, “The Comfort Zone for Men at Rest and Stripped to the Waist,” 165–79.
Richard J. de Dear and Gail S. Brager, “Thermal Comfort in Naturally Ventilated Buildings: Revisions to ASHRAE Standard 55,” Energy and Buildings 34, no. 6 (2002): 549–61; Richard J. de Dear et al., “Progress in Thermal Comfort Research Over the Last Twenty Years,” Indoor Air 23, no. 6 (2013): 442–61.
Richard J. de Dear and Gail S. Brager, “Developing an Adaptive Model of Thermal Comfort and Preference,” ASHRAE Transactions 104, no. 1 (1998). See also ASHRAE Standard: Thermal Environmental Conditions for Human Occupancy (2004); Fergus Nichol and Michael Humphreys, "New Standards for Comfort and Energy Use in Buildings," Building Research & Information 37, no. 1 (2009): 68–73.
Robert M. Malina and Bertis B. Little, “Physical Activity: The Present in the Context of the Past,” American Journal of Human Biology 20, no. 4 (2008): 373–74.
W. D. van Marken Lichtenbelt et al., “Cold-Activated Brown Adipose Tissue in Healthy Men,” New England Journal of Medicine 360, no. 15 (2009): 1505–07.
Leyla E. McCurdy et al., “Using Nature and Outdoor Activity to Improve Children’s Health,” Current Problems in Pediatric and Adolescent Health Care 40, no. 5 (2010): 105–06.
X. Liu et al., “Annual Performance of Liquid Desiccant Based Independent Humidity Control HVAC System,” Applied Thermal Engineering 26, nos. 11–12 (2006): 1198–1207.
P. S. Burge, “Sick Building Syndrome,” Occupational and Environmental Medicine 61, no. 2 (2004): 185–90.
Mae-ling Lokko, “Colonization of Air,” in Nature of Enclosure, ed. Jeffrey Nesbitt (Actar Publishers, 2022). See also Mae-ling Lokko, “Biomaterial Imaginaries,” AD Architectural Design: Biodesign in Architecture 96, no. 1 (2026): 49.
Alexandra R. Rempel and Alan W. Rempel, “Intrinsic Evaporative Cooling by Hygroscopic Earth Materials,” Geosciences 6, no. 3 (2016): 38.
Mae-ling Lokko and Alexandra Rempel, “Intrinsic Evaporative Cooling and Weather-Responsive Natural Ventilation for Adaptive Thermal Comfort in Tropical Buildings,” International Building Physics Conference, Syracuse: NY. IBPC (2018): 1415–16.
Fernando Pacheco-Torgal et al., eds., Toxicity of Building Materials (Elsevier, 2012), 9. See also Xiaoxiao Xu et al., “Bamboo Construction Materials: Carbon Storage and Potential to Reduce Associated CO2 Emissions,” Science of the Total Environment 814 (2022): 12.
Mae-ling Lokko, “Re-fusing: On Heat Regimes and Material Circularity,” Material Acts (e-flux Architecture, November 2024), ➝.
Richard de Dear, “Revisiting an Old Hypothesis of Human Thermal Perception: Alliesthesia,” Building Research & Information 39, no. 2 (2011): 108–17; Thomas Parkinson and Richard de Dear, “Thermal Pleasure in Built Environments: Physiology of Alliesthesia,” Building Research & Information 43, no. 3 (2015): 288–301.
Kathleen Scanlan, “Seeing Women in Stone: A Spatial Analysis of Lithic Technology and Use-Wear to Identify a Norton Tradition Ena on the Kvichak River, Bristol Bay, Alaska,” Journal of Northwest Anthropology 55, no. 1 (2021).
Kaarina Kailo, “Native Elders on the Sweat Lodge Today,” in Sauna Culture, Sweat and Spirituality: On the Architectonics and Cosmology of Sacred Space (Cham: Springer Nature Switzerland, 2025), 165.
Margaret Lantis, “The Social Culture of the Nunivak Eskimo,” Transactions of the American Philosophical Society 35, no. 3 (1946): 196.
Ashfaque Ahmad et al., “Bathing in History: A Comprehensive Study of the Ḥammām (Bathhouse) at Qutb Shahi Heritage Park, Hyderabad,” International Journal of Emerging Technologies and Innovative Research 11, no. 1 (2024): 617.
Mahboubeh Mahlouji et al., “Sweating as a Preventive Care and Treatment Strategy in Traditional Persian Medicine,” Galen Medical Journal 9 (2020): e2003.
Julie Peteet, The Hammam Through Time and Space (Syracuse University Press, 2024), 218–33.
Peteet, The Hammam Through Time and Space, 216–18.
