Clothing, abstract thought, food-gathering and shelter

Clothing is a cultural solution to a physiological problem. Humans have lost most body hair and cannot survive cold without insulation, so clothing substitutes for the fur that other mammals rely on.

Its consequence is large: it made cold, high-latitude environments habitable, and so it is one of the enablers of hominin dispersal out of the tropics.

The evidence is almost entirely indirect, because hides and fibres decay:

• Hide-working tools — scrapers used to clean skins, and awls for piercing them.
• Eyed needles, from roughly 40,000 years ago, which indicate tailored clothing sewn to fit rather than hides simply draped.
• Genetic evidence from clothing lice. Clothing lice live in clothing rather than on the body, so they could only have arisen once clothing existed. Dating the divergence of clothing lice from head lice therefore estimates when clothing came into regular use, giving a date well before the earliest needles.

The lice evidence is worth noting as an example of an indirect line reaching further back than the direct one — and of inference from a completely different kind of data.

Abstract thought means thinking about things not physically present — symbols, plans, and ideas that stand for something else. The Explanatory Notes group communication, language and art here.

Because thought does not fossilise, all evidence is of behaviour that implies abstraction.

Symbolic and artistic evidence:

• Pigments, especially ochre, ground and applied — implying decoration or marking with no practical function.
• Engraved objects with deliberate repeated patterns.
• Beads and ornaments, often of shell carried far from its source. Personal ornament implies communicating identity or status to others — the object stands for something.
• Cave paintings and figurines, representing animals and forms — a made object standing for something absent.
• Deliberate burial, sometimes with grave goods, implying ideas extending beyond immediate physical need.
• Musical instruments such as bone flutes.

Evidence relating to language, all indirect:

• Hyoid bone anatomy, which anchors muscles of the tongue and larynx.
• Endocranial impressions in regions associated with speech production and comprehension, and hemispheric asymmetry.
• The complexity of transmitted technology, which is easier to explain if instruction was possible.
• Genetic evidence from genes implicated in speech and language development.

None of these is direct evidence of language. Each is consistent with it. The honest position is that language is inferred from converging indirect lines, and that its timing is genuinely contested.

For almost all of hominin history, food was obtained by hunting and gathering — taking wild animals and plants.

• Groups were typically small, mobile, and moved to follow seasonal resources.
• Diets were broad, which buffers against the failure of any one resource.
• Little food could be stored or carried, so accumulating surplus was difficult.

Domestication — the selective breeding of plants and animals for human use — began roughly 11,000 years ago, and importantly arose independently in several regions, with different crops and animals in each. It was not a single event that spread from one place.

Domestication is artificial selection: humans choose which individuals breed, so the selection pressure is human preference rather than the natural environment. Selected traits included larger seeds, seed heads that do not shatter and so remain on the plant for harvest, reduced toxicity, and in animals docility and productivity.

The consequences were far-reaching:

• Sedentism. Crops must be tended and harvested in one place, so groups became settled.
• Food storage and surplus, which allowed populations to survive lean seasons and to grow.
• Population growth, because a settled group can support more children — mobile foragers must carry infants, which limits how closely births can be spaced.
• Permanent settlement, and eventually larger, denser communities.
• Occupational specialisation, since a surplus allows some individuals to do work other than food production.

The costs are equally important, and often omitted:

• Reduced dietary diversity, because a few staple crops replaced a broad wild diet, causing nutritional deficiencies visible in skeletal remains.
• Increased infectious disease, from living at higher density, in permanent settlements with accumulating waste, and in close contact with domesticated animals — the source of many human pathogens.
• Greater vulnerability to crop failure, since dependence on few staples removes the buffering a broad diet provides.
• Skeletal evidence from several regions shows reduced stature and more signs of nutritional stress in early farming populations compared with the foragers who preceded them.

So domestication increased the number of people an area could support while, at least initially, often reducing individual health. This is a genuinely important point: a practice can spread because it supports more people without making any individual better off.

The trend runs caves → temporary settlement → permanent settlement, and each step reflects increasing investment and control.

Caves and rock shelters — natural, requiring no construction. They preserve well, which is why they dominate the early record, though this is itself a preservation bias: open-air camps of the same period leave far less trace.

Temporary structures — built shelters occupied seasonally. Evidence includes postholes, arrangements of stones or bone weighing down coverings, and hearths with associated debris in patterns showing organised use of space.

Permanent settlement — substantial dwellings occupied year-round, with storage structures, and eventually villages. This follows domestication, because tending crops requires staying in one place.

Constructed shelter matters biologically because, like clothing and fire, it removes an environmental constraint: it allows occupation of places where the climate would otherwise be lethal, and it protects from predators and weather. Together these three are what made dispersal into cold regions possible.

• Directly on survival and reproduction. Clothing, fire and shelter allow survival in climates that would otherwise be lethal, so individuals possessing them survive and reproduce where others could not.
• On the biological capacity to acquire them. Individuals better able to learn, remember, teach and cooperate obtained these benefits more reliably, so alleles supporting those capacities increased in frequency.