Human Ecological Adaptations

• Human ecological adaptation is the set of biological and cultural adjustments through which human groups survive, reproduce and prosper in a particular environment.
  • It works at several levels at once: genes fixed by natural selection, physiology that adjusts within a lifetime, growth shaped by the conditions of childhood, and culture: clothing, shelter, food getting, mobility and social rules.
• Humans live in a greater variety of habitats than any other species: from the Sahara and the Kalahari to the Arctic tundra, the Tibetan plateau above 4,000 m, the Congo and Amazon rainforests and the open sea of South-East Asia.
  • This range is possible mainly because humans modify their surroundings instead of waiting for their bodies to change. Many visible biological traits are themselves responses to conditions humans created, such as dairying and farming.
• Adaptation is a two-way relationship. Every adaptive strategy also changes the ecosystem it depends on: fire, herding, shifting cultivation, terraces and irrigation have reshaped vegetation, soils and wildlife across the world.

Human Ecology and the Concept of Adaptation

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Ecology and human ecology

• The word ecology comes from the Greek oikos (house, habitat) and logos (study), the “science of the habitat”. The German zoologist Ernst Haeckel coined it in 1866.
  • It is the science of the interrelationships between organisms and their surroundings, abiotic and biotic.
  • All organisms live in accordance with the topographic, edaphic, climatic and hydrological conditions of their surroundings. The principles of ecology describe how these relations are organised.
• Ecology took shape with the systematic study of plants and animals, in Eugenius Warming‘s work on plant communities (1895; English 1909) and Charles Christopher Adams‘s guide to animal ecology (1913). Social scientists then carried its ideas to human populations.
  • The Chicago School of sociology, through Robert Ezra Park and Ernest Watson Burgess (1921), gave the term “human ecology” wide currency.
  • In geography, Harlan Barrows (1923) defined the discipline itself as human ecology. The longer history of the man–environment relationship runs from classical thought to political ecology.
• Roderick J. Lawrence (2001) gives the widely used definition: human ecology is the study of the dynamic interrelationships between human populations and the physical, biotic, cultural and social characteristics of their environment and the biosphere.
  • It is interdisciplinary, drawing on ecology, anthropology, sociology, biology, geography and economics.
  • Every society must adapt to the opportunities and constraints its environment presents, given its current culture.
  • Successful adaptation has occurred when a society can achieve all its important values over the long term without destroying its resource base.

The anthropological view: adaptation through culture

• The anthropologist June Helm (1962) described the ecological approach as the study of the adaptive ordering of the relations of human groups to the natural environment, with its demographic and socio-cultural conditions and consequences.
  • Its first level is man in adjustive and exploitative interaction, through technology, with the physical and living environment.
  • This shapes the second level: relations among human beings themselves, such as kinship, labour and property.
• Anthropologists hold that the environment’s contribution to culture is subordinate to ordering principles such as kinship, social norms, ritual and symbolism.
  • The ecological approach is used to explain cultural diversity, not to reduce culture to environmental causes. This is the main break from the older environmental determinism.
• The human paradox: humans are the dominant species on Earth, yet they are not the best species for studying the full range of biological adaptation.
  • Their intellectual capacity lets them adjust behaviour to conditions, so humans show more cultural adjustment than biological adaptation.
  • Even so, clear biological variation exists among populations in different climates. Skin colour, an adaptation to ultraviolet radiation, is the best example; body size and shape also vary with climate.

Adaptation, acclimation and acclimatisation

• Humans differ from other organisms in using regulators to define, modify and control their living conditions.
  • Inside the body these include thermoregulation and circadian rhythms. Outside it they include fire, clothing, housing and technology.
  • Adaptation is therefore the product of biological, ecological, cultural, social and individual mechanisms working together.

• The key distinction: adaptation changes the genotype and is permanent; acclimatisation changes the phenotype and fades when the stress is removed, though the capacity to acclimatise is itself inherited.
• Cultural adaptation is the alternative to physiological change. A protective layer, such as clothing or shelter, reduces or removes the stress itself, so the body does not have to respond.

Environmental stress and the adaptive response

• Adaptation follows a chain: environmental stress → strain on the organism → adaptive response.
  • For example, low oxygen at altitude (stress) strains breathing and circulation (strain), and the body answers with faster breathing and more red blood cells (response).
  • Adaptation is thus brought about by strain, which is caused by environmental stress.

Abiotic and biotic stresses

Levels of adaptation

• Adaptations range from the genetic to the cultural. Each level differs in permanence, speed and scope.
  1. Genetic level: changes in the genetic make-up of a population over generations through natural selection. These are the most permanent.
     • Examples: skin colour as an adaptation to ultraviolet radiation; lactase persistence in dairying peoples.
  2. Physiological level (acclimatisation): changes during an individual’s lifetime in response to stress. The ability has a genetic basis, but the response appears only when the stress is felt.
     • Example: tanning; more sweating after two weeks in the heat.
  3. Growth and development level (developmental acclimatisation): changes made during the period of growth. They are more lasting than physiological ones because they alter how some part of the body grows.
     • Example: larger lung capacity in people raised at high altitude.
  4. Cultural level: a protective microenvironment that minimises or removes the stress, usually achieved by changing behaviour.
     • Examples: Inuit clothing, which creates its own microclimate; air conditioning; irrigation in desert farming.

Biological versus cultural adaptation

• The two are linked. Cultural change creates new selective pressures; dairying, for instance, selected for lactase persistence, and farming in cleared forest spread malaria and selected for the sickle-cell trait.
• Over history the balance has shifted from biology towards culture, through the stages of human adaptation from hunting and gathering to the industrial and information age.

Biological Adaptation to Climate, Altitude and Diet

Ecogeographic rules in human populations

• Most ecogeographic rules date from the nineteenth century, when naturalists noticed that the form of many warm-blooded species varies regularly with climate. Three rules apply to human populations. Their wider use in plants and animals belongs to the kinds of ecological adaptation.

Gloger’s rule and skin colour

• Constantin Wilhelm Lambert Gloger (1833) observed that races of birds and mammals in warm, humid regions are more darkly pigmented than those in cold or dry regions. It holds for wolves, foxes, tigers and hares as well.
• Among humans, populations nearer the equator are generally darker-pigmented.
  • Peoples of equatorial Africa, South Asia and Melanesia carry more melanin than northern Europeans. Melanin is a natural ultraviolet filter.
• Nina Jablonski and George Chaplin (2000) explained the cline as a balance between two vitamins:
  • Dark skin protects folate, which ultraviolet radiation destroys and which is vital for fetal development;
  • Light skin at high latitudes lets weak ultraviolet light make enough vitamin D.
  • The Inuit are a telling exception: fairly dark for their latitude, because a diet of fish and marine mammals supplies vitamin D.

Bergmann’s rule

• Carl Bergmann (1847), the size rule: within related species of birds and mammals, those in cold climates are larger.
• The physics: as a body grows, its surface area rises by the square but its volume by the cube. A larger body has a lower surface-area-to-volume ratio and keeps heat better.
• Human examples: body mass tends to rise with latitude. Northern European populations are heavier on average than southern ones, and Arctic peoples are heavy and compact for their height.
  • Caution: stature also depends heavily on nutrition and health, so the rule shows clearly in body mass and shape, less in height.

Allen’s rule

• Joel Asaph Allen (1877), the proportion rule: protruding parts (limbs, ears, tails, bills) are shorter in cold regions and longer in warm ones.
  • Short extremities cut heat loss; long ones help dissipate heat.
• Human examples: the Nilotic peoples of South Sudan and East Africa (Dinka, Nuer, Maasai) are tall and slender with long limbs, which helps shed heat. Inuit have short limbs and a stocky trunk.

Adaptation to heat

Thermoregulation

• Body heat comes from the oxidation of carbohydrates and fats. The body balances heat produced and absorbed against heat lost by radiation, convection, conduction and evaporation.
• Core temperature is held close to 37 °C, normally within about a degree.
  • Below about 35 °C a person is hypothermic; above about 40 °C heat stroke threatens, and above 41–42 °C cells are damaged.
• Heat stress arises from the interaction of air temperature, humidity, sunshine, work rate and heavy clothing or equipment that blocks heat loss.
• Two parallel systems keep the core stable:
  • Physiological thermoregulation works without conscious choice. It controls metabolic heat production, the flow of warm blood from core to skin, and sweating. It matters most in heat stress.
  • Behavioural thermoregulation works through conscious action: changing activity, clothing and shelter. It matters most in cold stress.

Physiological mechanisms in heat

• Sweating: sweat glands switch on as body temperature rises. Sweating begins on the trunk and spreads to the limbs, and evaporation carries heat away.
  • In hard work in the heat, evaporation removes most of the heat, above about 80% of it.
  • Humidity limits sweating. In humid heat sweat drips instead of evaporating, so hot-humid climates are more dangerous than hot-dry ones at the same temperature.
• Vasodilation: skin blood vessels widen, carrying more warm blood from the core to the surface.
• Cardiovascular response: as blood pools in the skin, the heart rate rises to keep up cardiac output, and the baroreflex holds blood pressure steady.
• Heat acclimatisation, over about one to two weeks:
  • sweating starts earlier and becomes more profuse;
  • sweat becomes more dilute, so less salt is lost;
  • plasma volume expands, and heart rate and core temperature during work fall.
• Developmental and genetic traits:
  • The number of active sweat glands is set in early childhood by the climate a child grows up in.
  • Linear body build (Allen’s rule) raises the surface-area-to-mass ratio for heat loss.

Factors in individual heat tolerance

• Age: older adults sweat less and raise skin blood flow less, so heat waves strain them most.
• Physical activity: strenuous work raises metabolic heat production up to 10–20 times above rest.
• Body shape and fat: a slender build sheds heat easily; obesity adds tissue to warm and relatively less skin to lose heat through.
• Acclimatisation and fitness: fit, acclimatised people tolerate heat far better than newcomers.
• Social conditions: housing, outdoor work, access to water and cooling, and poverty decide who suffers most. The urban heat island adds to the stress in cities.
  • India’s first Heat Action Plan (Ahmedabad, 2013) turned this knowledge into early warnings, cool shelters and changed working hours.

Adaptation to cold

Three patterns of cold adaptation

• Human adaptations to chronic cold are more modest and less understood than those to heat. Heat produces a fairly uniform set of changes; chronic cold produces three different patterns:
  • Habituation: the commonest pattern. Physiological responses are blunted: people shiver less and constrict skin vessels less, so hands stay warmer and more useful.
  • Metabolic adaptation: heat production rises, including non-shivering thermogenesis in brown adipose tissue.
  • Insulative adaptation: heat is conserved through subcutaneous fat and stronger constriction of skin vessels.
    • Aboriginal Australians of the central desert, sleeping out on cold nights, let skin and core temperature fall slightly without shivering: an insulative, energy-saving pattern.

Physiological mechanisms in cold

• Shivering: graded muscle activity, from raised muscle tone to violent shivering. With vasoconstriction, it delays the fall in body temperature.
• Vasoconstriction: cold activates the sympathetic nerves, which narrow the vessels of skin and limbs and keep warm blood in the core.
  • Cold-induced vasodilation periodically rewarms the fingers. It is strong in the Inuit and in fishers who work with wet hands, protecting them against frostbite.
• Non-shivering thermogenesis: brown adipose tissue burns fat to make heat directly. Cold exposure stimulates it through noradrenaline released from the sympathetic nerves.
• High metabolic rate: circumpolar peoples such as the Inuit, Evenki and Buryat have basal metabolic rates above predicted values. This comes from a high-protein, high-fat diet, acclimatisation and genetic factors.
• Cardiovascular reflexes:
  • Cold on the hands raises heart rate and blood pressure.
  • Cold on the face slows the heart: the diving reflex used by breath-hold divers.

Factors affecting cold tolerance

• Body size and shape: a large, compact body needs less heat per kilogram to stay warm.
• Subcutaneous fat: the most important natural insulation. A thicker layer keeps the skin cooler and narrows the gradient between body surface and air.
• Fitness and age: fit and young people respond better, through better blood supply and higher metabolic rate; the elderly are vulnerable to hypothermia.
• Nutrition: undernourished people respond poorly, with weak heat production and more intense shivering.

Adaptation to high altitude

High-altitude stresses

• Land above about 2,500 m is usually treated as high altitude. Some 80 million people or more live permanently above this height, chiefly on the Tibetan plateau, the Andean altiplano and the Ethiopian highlands.
• The high-altitude environment brings seven stresses: hypoxia, intense solar and ultraviolet radiation, cold, low humidity, high winds, a limited food base and rough terrain.
• Physiologically, hypoxia is the decisive stress, because the others occur equally or more severely elsewhere. It is also the one stress that culture cannot remove: no hut or clothing restores the missing oxygen.

Hypoxia and its effects

• Hypoxia is the shortage of oxygen in the tissues caused by the fall in the partial pressure of oxygen with height.
  • The air still holds about 21% oxygen, but air pressure falls: at 4,000 m it is about 60% of sea level, and on the summit of Everest about one-third.
  • Every organ system is affected.
• Acute mountain sickness in newcomers: headache, loss of appetite, nausea, vomiting, fatigue, weakness, dizziness and disturbed sleep. In severe cases fluid gathers in the lungs or brain.
• Acclimatisation in lowlanders:
  • breathing deepens and quickens within hours;
  • the heart rate rises;
  • haemoglobin and haematocrit rise over weeks, increasing the blood’s oxygen-carrying capacity.
• Chronic mountain sickness (CMS), also called Monge’s disease, excessive erythrocytosis or chronic soroche:
  • It was described by the Peruvian physician Carlos Monge Medrano in 1925.
  • The body makes too many red blood cells. The blood thickens, oxygen in the blood falls, and the right heart is strained. Symptoms include headache, breathlessness, poor sleep and muddled thinking.
  • It usually appears in adult men, after the third decade of life.
  • It affects more than 10% of adults in high Peruvian towns (about 15% at Cerro de Pasco, 4,300 m). It is less common among Tibetans and has not been described among Ethiopian highlanders.
• Pregnancy:
  • Hypoxia lowers birth weight and raises the risk of pre-eclampsia (high blood pressure with protein in the urine), a major cause of maternal and fetal death at altitude.
  • Andean and Tibetan mothers increase blood flow to the uterus more than European or Han Chinese mothers at the same altitude, so their babies are better protected from growth restriction.

Three highland patterns: Andes, Tibet and Ethiopia

• High plateaus were settled independently in three regions: the Tibetan plateau from about 25,000 years ago or earlier, the Andean altiplano from about 11,000 years ago, and the Ethiopian highlands.
  • Each population met the same stress in different ways. This is the clearest case of convergent adaptation in humans, worked out mainly by Cynthia M. Beall and her colleagues.

• Andean pattern: the “classic” response: more haemoglobin to carry more oxygen. It works, but the cost is thicker blood and a higher risk of CMS.
• Tibetan pattern:
  • Tibetans keep haemoglobin near sea-level levels and instead breathe more and move blood faster through wider vessels.
  • Variants of EPAS1 and EGLN1, genes of the body’s oxygen-sensing pathway, dampen the red-cell response.
  • The Tibetan EPAS1 variant entered the human gene pool through interbreeding with Denisovans, an archaic human group (2014).
• Ethiopian pattern:
  • Amhara highlanders at 3,530 m in the Semien Mountains have haemoglobin and oxygen saturation close to sea-level values. Cynthia M. Beall and colleagues reported this in 2002; the mechanism is still unclear.
  • Their Oromo neighbours at similar heights, who arrived more recently, show raised haemoglobin. Ancestry, not altitude alone, decides the response.
• Developmental adaptation: children growing up at altitude develop larger chests and lung volumes, whatever their ancestry. Andean highlanders show this most clearly.
• Lesson: biological adaptation follows different routes to the same end. One environment does not dictate one human form.

Factors affecting the response to altitude

• Age: in the first days at altitude, young people raise haemoglobin faster than older people.
• Physical fitness: fit people tolerate hypoxia better. Exercise builds more capillaries, a higher maximum aerobic capacity, and larger skeletal and heart muscles.
• Ancestry and early life: highland ancestry and a childhood at altitude both improve performance, as the three patterns show.

High-altitude studies and medicine

• Hypoxia occurs in many diseases: ischaemic heart disease, stroke, anaemia, chronic obstructive pulmonary disease and pulmonary hypertension.
• Understanding how highlanders cope helps medicine manage the response of tissues to low oxygen. The oxygen-sensing pathway of EPAS1 and EGLN1 is now a target for drugs against anaemia.

Nutritional and genetic adaptation to diet and disease

• Nutrition underpins every other adaptation. Metabolic responses to heat, cold and altitude all raise food needs, and poor nutrition weakens them.

• Genetic adaptations to diet:
  • Lactase persistence: the ability to digest milk sugar in adulthood. It spread with dairying in northern Europe, among East African pastoralists such as the Maasai, and in the Middle East and South Asia. Different mutations arose in different regions.
  • Greenland Inuit carry variants of the fatty-acid-processing genes (FADS) suited to a diet rich in omega-3 fats from fish and marine mammals (2015).
  • Peoples with starch-rich diets tend to carry more copies of the salivary amylase gene.
• Genetic adaptation to disease:
  • The sickle-cell trait gives partial protection against falciparum malaria. It is common in parts of tropical Africa and in some tribal populations of central India.
  • Forest clearance for farming spread malaria, so here a cultural change created the selective pressure. Disease ecology and its links with environment and human health follow the same logic.

Cultural Adaptation by Environment Type

Principles of cultural adaptation

• Human adaptive techniques are of two kinds:
  • Material culture: dwellings, clothing and tools that build a favourable microclimate. They block radiant, convective and conducted heat gain or loss.
  • Behaviour: chiefly avoidance, such as resting at midday, moving with the seasons, or timing work and travel.
• Each strategy is tuned to the limiting factor of its environment:
  • water and heat in deserts;
  • cold and darkness in the Arctic;
  • oxygen and short seasons in mountains;
  • dense cover and poor soils in rainforests;
  • seasonal grass in savannas;
  • the monsoon rhythm in South and South-East Asia;
  • the sea on coasts.
• The same world biomes that set plant and animal life set the frame for these strategies. Indian examples come from the country’s many tribal communities.

Hot deserts

• Limiting factors: extreme day heat, cold nights, intense radiation, scarce and uncertain water, and sparse food.
• Material culture in hot-dry lands:
  • High heat-capacity walls: thick walls of adobe (mud brick) and stone absorb heat by day and release it at night.
  • Underground living: the subsoil is far cooler than the surface by day, so people dig in, as in the pit houses of Matmata (Tunisia) and the cave dwellings of Coober Pedy (Australia).
  • Compact settlements: houses packed together around narrow lanes and inner courtyards shade one another’s walls and cut exposure to wind and sun.
  • Few, small, shuttered windows limit heat entry. Whitewashed surfaces reflect sunlight.
  • Cooking outside or in separate kitchens keeps heat out of living rooms.
  • Wind-catchers (badgir) in Iran and the Gulf funnel breezes into rooms. Qanats, gently sloping underground tunnels, carry groundwater to oases without losing it to evaporation.
  • Loose, flowing, covering clothing:
    • it prevents sunburn and abrasion;
    • it cuts solar heat gain, so the body needs to sweat less;
    • a layer of air between cloth and skin carries heat away.
• Bedouin (Arabia, Sinai, the Negev):
  • Camel and goat herders who live in the black goat-hair tent. Its dark roof shades deeply, its weave lets hot air escape, and its sides open or close with the wind.
  • They move between wells and seasonal pastures. The camel supplies milk, meat, hair and transport.
• Tuareg (central Sahara): men wear the indigo tagelmust, a veil that guards against sand and cuts moisture loss in breathing. They traditionally controlled caravan trade across the desert.
• San (Kalahari):
  • Hunter-gatherers who store water in ostrich eggshells buried in the sand, draw it through sip-wells, and get moisture from tsamma melons and roots.
  • Their small, mobile bands follow game and rain, and their knowledge of hundreds of plants and animal tracks is the core of their adaptation.
• Aboriginal Australians of the Western Desert: highly mobile foragers who know every rock hole and soakage. They use fire to manage vegetation and renew game.
• Thar Desert, India:
  • Raika (Rebari) camel and sheep pastoralists move with the rains.
  • Bishnoi villages protect khejri trees and blackbuck.
  • Water is harvested in kunds (tankas), johads and khadin runoff fields.
  • In Kachchh, the circular mud bhunga keeps cool and withstood the 2001 earthquake better than many modern buildings.
• Biological adjustments support the cultural ones: heat acclimatisation, efficient sweating and, in long-resident peoples, a slender build.

Cold deserts and tundra

• Limiting factors: long, severe winters, months of darkness, wind chill, frozen ground, a short growing season and almost no plant food.
• Inuit of Arctic Canada, Alaska and Greenland, the classic case:
  • Clothing:
    • Two layers of caribou or seal skin: the inner layer has the fur inwards and the outer layer the fur outwards, with air trapped between them as insulation.
    • The outer layer is windproof and water-resistant. Wide openings closed by drawstrings let the wearer vent heat and moisture before sweat soaks the fur.
  • Footwear:
    • Sealskin boots (kamik) are stitched with sinew without piercing right through, so they stay waterproof.
    • Fur stockings and a grass pad in the sole soak up sweat and meltwater.
    • Sealskin mittens carry grass pads too.
  • Shelter:
    • The snow house (iglu) is a hunting shelter, built on journeys. Snow is full of tiny air cells and insulates well.
    • A raised sleeping platform holds the warmest air. A seal-oil lamp (qulliq) gives heat and light and melts snow for water.
    • The interior can stay tens of degrees warmer than the air outside.
  • Winter houses: semi-underground, built of stone, whalebone or driftwood, covered with turf and snow, on sheltered hillsides, with vent holes to stop overheating.
  • Diet:
    • seal, whale, walrus, caribou and fish;
    • fat for energy;
    • raw meat, organs and whale skin (muktuk) supply vitamin C and vitamin D that plants cannot.
  • Mobility: the kayak and the larger umiak on water, the dog sledge on ice, and seasonal camps that follow seals, caribou and fish.
• Sami of northern Scandinavia and Nenets of the Yamal Peninsula: reindeer herders who follow the herds between winter forest and summer tundra, living in the conical lavvu and chum tents.
• Biological traits:
  • a compact body with short limbs;
  • a high basal metabolic rate;
  • strong cold-induced vasodilation in the hands;
  • FADS variants for a fat-rich diet.

High mountains and plateaus

• Limiting factors: hypoxia, cold, strong radiation, steep slopes, thin soils, short growing seasons and isolation.
• Sherpa of the Khumbu, around the foot of Everest in Nepal:
  • Houses are two-storeyed stone buildings clustered in the middle of village farmland, with flat plank roofs held down by heavy stones. Livestock live below, and their warmth rises to the family above.
  • Men and women wear a long woollen robe over trouser-like garments and high woollen boots with hide soles.
  • They grow potato and barley and herd yak and yak–cattle hybrids between summer high pastures and winter villages. Trading and, today, mountaineering and trekking support the economy.
• Aymara and Quechua of the Andean altiplano, around Lake Titicaca (Peru and Bolivia):
  • Houses are oblong, of adobe, with roofs of reed and grass thatch. Around the lake, totora reeds make boats and, among the Uros, floating islands.
  • On the altiplano men wear woollen caps with ear flaps and ponchos; women wear home-spun skirts and shawls.
  • They farm potato (freeze-dried as chuño for storage), quinoa and other hardy crops. They herd llama and alpaca, and grow crops in raised fields (waru waru) that store heat.
  • Andean terraces hold soil and water on steep slopes.
• Indian Himalaya:
  • Changpa of the Changthang plateau in eastern Ladakh, at about 4,500 m and more:
    • Nomadic herders of pashmina (Changthangi) goats, sheep and yak.
    • They live in yak-hair rebo tents and move between fixed seasonal pastures around Tso Moriri, Tso Kar and Pangong Tso, through winters far below freezing.
    • The fine underwool of their goats is the raw material of pashmina.
  • Gaddi of the Dhauladhar range, Himachal Pradesh: transhumant shepherds of sheep and goats.
    • They take their flocks to high pastures in Chamba, Bara Bhangal, Lahaul and Spiti in summer.
    • In winter they come down to the foothills of Kangra, Una, Bilaspur, Hamirpur and Sirmaur.
  • Bhotia traders of Uttarakhand and Monpa of Arunachal Pradesh combine yak herding, terrace farming and trans-Himalayan exchange.
• Common mountain strategies: vertical zonation of land use (fields low, forest in the middle, pasture high), seasonal movement, stone houses with livestock below, woollen clothing, stored grain and dried food, trade across passes, and community rules for pasture and forest.
  • The ecology of mountain environments and their hazards frames all of these.

Equatorial rainforests

• Limiting factors: constant heat and high humidity, which hampers sweating; dense cover; poor, leached soils; and many diseases and parasites.
• Forest foragers of Central Africa: the Mbuti of the Ituri forest (DR Congo), the Baka of Cameroon and the BaAka of the Central African Republic.
  • They are often grouped under the old, now disfavoured term “Pygmy“.
  • They live by net and bow hunting, gathering honey, nuts and tubers, and exchange with neighbouring farming villages.
  • Dome-shaped huts of saplings and leaves are built in hours and abandoned when the camp moves.
  • Their short stature, linked to the growth-hormone pathway, has several proposed explanations: easier heat loss in humid heat, lower food needs, movement through dense undergrowth, and an early-maturing life history suited to high mortality.
• Amazonia: the Yanomami of the Brazil–Venezuela border live in the round communal shabono. They combine slash-and-burn gardens of plantain and manioc with hunting, fishing and gathering.
• South and South-East Asia:
  • the Semang (Batek) of Malaysia and the Penan of Borneo are forest foragers;
  • in India, jhum (shifting cultivation) in the north-eastern hills, and the Baiga and Kadar of the central and Western Ghats forests.
• Shifting cultivation is the characteristic adaptation to poor tropical soils:
  • A forest patch is cut and burnt. The ash fertilises the soil for one to three years of mixed cropping.
  • The plot is then left fallow for the forest and soil to recover, while a new patch is cleared.
  • Mixed cropping keeps the ground covered and spreads risk.
  • It is one of the farming types of the world’s agricultural regions.
• Material culture: raised, open-sided houses of light timber and thatch for air flow, steep roofs that shed heavy rain, and little clothing, which lets sweat evaporate.

Grasslands and savannas

• Limiting factors: a long dry season, variable rain, grass that is edible only to livestock and game, and predators.
• Maasai of southern Kenya and northern Tanzania:
  • Semi-nomadic cattle herders whose wealth, diet and ritual centre on cattle.
  • Their traditional diet relies on milk, meat and blood, which they draw from a living animal.
  • The homestead (enkang) is a ring of low huts of branches, mud and cow dung inside a thorn-bush fence that also protects the cattle at night from lions.
  • Herds move between wet-season and dry-season grazing, spreading the pressure on grass.
• Fulani of the Sahel: transhumant cattle herders who follow the rains north and retreat south to rivers in the dry season.
• Mongol and Kazakh herders of the Central Asian steppes:
  • They move horses, sheep, goats, cattle and camels between seasonal camps.
  • The portable felt ger (yurt) goes up in an hour.
  • The steppe grasslands of the world support a range of such mobile pastoral systems.
• India:
  • Toda of the Nilgiris: buffalo herders who live in small hamlets (munds) of barrel-vaulted huts of cane, bamboo and thatch with tiny doorways that keep in warmth. Their sacred dairies and buffalo rituals bind their culture to the shola–grassland landscape.
  • Gujjar and Bakarwal of Jammu and Kashmir: buffalo and goat herders who migrate seasonally to high pastures.
  • Rabari of Gujarat and Rajasthan: herders of camels, sheep and cattle.
• Common strategies: mobility; herd diversity, mixing grazers and browsers to spread drought risk; reciprocal grazing rights; portable dwellings; and a diet built on milk, the renewable product of the herd.

Monsoon lands

• Limiting factors: a wet season of floods and a dry season of drought, with year-to-year variability; dense populations depend on one rainy season.
• Wet-rice cultivation is the central adaptation:
  • bunded paddy fields hold monsoon water;
  • nursery transplanting times the crop to the rains;
  • buffaloes do the ploughing in mud.
  • On hill slopes, terraces turn rain into stored water, as in Java, Bali and the Ifugao terraces of the Philippines.
• Stilt houses raised on posts keep people above floods and damp ground.
  • The Mishing of the Brahmaputra floodplain and Majuli build bamboo chang ghar on stilts.
  • In Bihar and Bengal, people raise house plinths and keep boats.
• Apatani of the Ziro valley, Arunachal Pradesh:
  • They grow wet rice together with fish in the same paddy plots, without draught animals or machines.
  • They manage bamboo and pine groves and channel streams through the valley.
• Kuttanad in Kerala farms below sea level, using dykes and polders. It is recognised by the FAO as a Globally Important Agricultural Heritage System.
• Water harvesting carries the monsoon into the dry season: the tanks (eri) of Tamil Nadu and Karnataka, the ahar–pyne of south Bihar, and the zabo of Nagaland, which joins forest, ponds and paddy in one runoff system.
• The monsoon itself, with its onset, breaks and failure, sets the rhythm of festivals, migration and work.

Coasts and islands

• Limiting factors: dependence on the sea; storms, cyclones and tsunamis; scarce fresh water on small islands; limited land.
• Bajau “sea nomads” of the Philippines, Malaysia and Indonesia:
  • They live on houseboats and stilt villages and free-dive for fish for hours a day, to depths of tens of metres.
  • They have spleens about 50% larger than their land-dwelling neighbours, linked to a gene variant (PDE10A). The spleen stores oxygen-rich red cells and squeezes them out during a dive (2018).
  • This is the first genetic adaptation to diving known in humans.
• Moken of the Andaman Sea: sea nomads whose children see more sharply underwater by constricting the pupil. Their knowledge of a receding sea saved many lives in the 2004 tsunami.
• Andaman and Nicobar Islands, India:
  • Jarawa of South and Middle Andaman and Onge of Little Andaman are hunter-gatherers of forest, creek and reef. They hunt pig and turtle, fish with bows and arrows, and gather honey and tubers.
  • The Sentinelese of North Sentinel Island still live in isolation.
  • The Onge and Jarawa moved to high ground before the 2004 tsunami, reading the sea’s withdrawal.
  • The island territories face special pressures of development on such groups.
• Indian coasts: the Koli fishers of the Konkan, the kattumaram (catamaran) of the Coromandel fishers, and the coral-stone houses of Lakshadweep, with rainwater stored for the dry months.

Summary of cultural adaptations

Impacts of Human Adaptations on Ecology and Environment

• Every adaptive strategy draws on an ecosystem and changes it. The outcome depends on population density, technology, institutions and the pace of change.
  • Low numbers, mobility and long fallows usually let ecosystems recover. Rising numbers, sedentarisation and market pressure turn the same strategies into agents of degradation.
  • This wider influence of man on ecology and environment grew with each technological stage.

Adaptations that sustain ecosystems

• Mobility and rotational grazing:
  • Maasai, Fulani, Gaddi and Changpa herds move before pastures are exhausted.
  • Seasonal grazing and manure keep grasslands open, recycle nutrients and support wild grazers alongside livestock.
• Long-fallow shifting cultivation: with fallows of 15–20 years or more, the forest regrows, soil fertility recovers and the patchwork of plots of different ages raises biodiversity.
• Terraces and water systems:
  • Andean, Ifugao, Apatani and Himalayan terraces, the qanat and the khadin hold soil and water on slopes and in drylands for centuries.
  • Apatani rice–fish fields recycle nutrients with no chemical inputs.
• Sacred groves and taboos:
  • Sacred groves (the devrai of Maharashtra, the kavu of Kerala, the law kyntang of Meghalaya) protect patches of old forest and springs.
  • The Bishnoi guard khejri and blackbuck, remembered in the Khejarli sacrifice of 1730.
  • Such values link directly to deep ecology and environmental ethics.
• Fire as a management tool:
  • Aboriginal “fire-stick farming“, named by Rhys Jones (1969), burns small patches in the cool season.
  • It creates a mosaic that prevents large, hot wildfires and renews grazing for game. Australia now uses Indigenous fire management again.
• Traditional ecological knowledge: detailed knowledge of plants, animals, weather and the sea, as in the Moken and Onge reading of the 2004 tsunami, is now valued for conservation and disaster risk reduction.

Adaptations that degrade ecosystems

• Hunting and fire in prehistory:
  • The overkill hypothesis of Paul S. Martin (1967) links the extinction of mammoths, giant ground sloths and other megafauna to the arrival of human hunters in the Americas and Australia.
  • Climate change also played a part, and the balance is still debated.
  • Repeated burning converted forest to grassland in places.
• Overgrazing:
  • When herds grow, mobility is restricted, or wells concentrate animals, grass cover fails. Soil erodes and desertification sets in.
  • The Sahel after the droughts of the late 1960s to the 1980s is the classic case, worsened by deep boreholes that drew herds to one spot.
  • The Thar margins of western Rajasthan show the same pattern.
• Short-cycle shifting cultivation:
  • As population grows, fallows shrink from 20–30 years to as little as 3–5 years in parts of north-east India.
  • The forest cannot regrow, so soil erodes, weeds and bamboo invade, and yields fall.
  • The result is deforestation and degraded hill slopes.

• Irrigation without drainage:
  • In ancient Mesopotamia, salt left by irrigation forced a shift from wheat to salt-tolerant barley and helped farming decline in the south, as Thorkild Jacobsen and Robert McCormick Adams (1958) showed. Modern canal commands repeat it as waterlogging and salinity.
• Island overuse: small, isolated islands have little margin; the deforestation of Rapa Nui (Easter Island), by clearance and introduced rats, is the much-debated example.
• Fuelwood and grazing in mountains:
  • Around high settlements and trekking routes, demand for fuelwood and fodder thins forest and scrub.
  • On the Changthang, rising goat numbers for the pashmina market add grazing pressure, and herders find themselves in conflict with wild herbivores such as the kiang.

Modern pressures on traditional adaptations

• Sedentarisation and land loss: states, ranches, farms and protected areas have cut pastoral and foraging ranges. Maasai rangelands have shrunk through subdivision of group ranches and conservation areas, and forest foragers of Central Africa have been pushed out of parks.
• Market integration: cash crops, wage work and commercial demand (for pashmina, bushmeat, timber or tourism) change what people take from the land and how fast; trucks replace pack animals, and canvas replaces yak-hair tents.
• Contact and health: isolated groups such as the Jarawa face disease and dependence through contact, and the Andaman Trunk Road through their reserve brings traffic and intrusive tourism.
• Climate change is undercutting adaptations built for a stable climate:
  • The Arctic is warming about four times faster than the global average. Thinner, shorter-lived sea ice makes Inuit hunting and travel dangerous.
  • Inuit also carry high body loads of mercury and persistent organic pollutants that biomagnify up the marine food chain from distant industry.
  • Gaddi routes face shifting snowlines, cloudbursts and hailstorms that kill flocks in the high pastures.
  • Changpa face warmer winters, thinner lake ice and poorer wool, and snow disasters that kill livestock.
  • Sahelian and East African herders face longer droughts. Coastal and island peoples face sea-level rise and stronger cyclones.
• These changes form part of the wider global and regional ecological changes of the Anthropocene.

Adaptation and climate change today

• The IPCC Sixth Assessment Report (2021–23) defines adaptation in human systems as adjustment to actual or expected climate and its effects, to moderate harm or exploit beneficial opportunities.
  • Incremental adaptation keeps a system working, as with new crop varieties or heat action plans.
  • Transformational adaptation changes its fundamental attributes, as with relocation or a new livelihood.
• Maladaptation is adaptation that raises risk or vulnerability instead of reducing it, or shifts the burden to others: sea walls that destroy mangroves, or air conditioning that adds to emissions.
• The IPCC gives weight to Indigenous and local knowledge as a source of tested adaptive strategies. Heat action plans, community seed banks, revived water harvesting and Ladakh’s ice stupas, artificial glaciers that store winter meltwater for spring sowing, build on it.

Evaluation

• Culture outweighs biology in human adaptation. It is faster, transferable and far more powerful, which is why humans occupy every biome. Biological traits matter most where culture cannot remove the stress, as with hypoxia.
• No environment dictates a single response. Three different highland patterns, many different desert and Arctic technologies, and the contrasting fortunes of the same strategy under low and high pressure all support a possibilist and ecological reading over strict determinism.
• Adaptation and degradation are two faces of one process. A strategy that suits small, mobile populations can degrade land under crowding, sedentarisation or market demand. Sustainability is a property of the whole system (people, numbers, rules and technology), not of the technique alone.
• Traditional adaptations are under strain from outside forces. Climate change, land loss and globalisation have tightened the limits. The best responses combine local knowledge, secure land and resource rights, and modern science.