Tools and the use of fire
What cultural evolution is
-
Cultural evolution is change in learned, transmitted behaviour — skills, knowledge and practices passed between individuals and generations by teaching and imitation.
-
It differs from biological evolution in three ways that matter:
- It is transmitted by learning, not by inheritance of alleles.
- It can pass sideways between unrelated individuals, and to many at once, not only from parent to offspring.
- It is therefore much faster — a useful innovation can spread through a population in a single generation.
-
The two interact. Culture changes the environment an organism experiences, which changes the selection pressures acting on it. Cooking, for example, is a cultural practice that altered selection on teeth and jaws.
The trend in tools
-
The Explanatory Notes cover tools of stone, wood and bone. Stone dominates the record simply because it preserves; wood and bone rarely survive, so the record understates their use.
-
The overall trend has four strands, and describing these is more useful than naming industries:
- Increasing complexity of manufacture — from a few flakes struck off a cobble to shaped, standardised, multi-part tools.
- Increasing standardisation — later tools are made repeatedly to a consistent pattern, indicating a mental template and deliberate design.
- Increasing range of materials — stone alone, then bone, antler and ivory, which can be carved into forms stone cannot take.
- Increasing specialisation — general-purpose cutting edges give way to distinct tools for distinct jobs, and eventually to composite tools of several parts hafted together.
-
The broad sequence:
- Earliest stone tools (from roughly 2.6 million years ago) — simple flakes struck from a core, with sharp edges for cutting, and choppers. Few steps, little standardisation.
- Shaped bifacial tools (from roughly 1.7 million years ago) — worked on both faces to a deliberate symmetrical form, such as handaxes. This requires many controlled strikes and a template held in mind.
- Prepared-core techniques (from roughly 300,000 years ago) — the core is shaped first so that a flake of predetermined size and shape can be struck off. This is a substantial cognitive step: the maker must plan several stages ahead toward a product that does not yet exist.
- Blade and composite tools (from roughly 50,000 years ago) — long thin blades struck from prepared cores, small microliths set into wooden or bone handles, and extensive use of bone and antler for points, harpoons and needles.
-
Composite tools matter most. Combining materials — a stone point, a wooden shaft, a binding — requires assembling components made separately, each useless alone. That implies planning across time and, almost certainly, teaching.
Why better tools were advantageous
- More energy obtained. Cutting meat from carcasses and breaking bones for marrow gave access to energy-dense food unavailable to teeth alone. Digging sticks reached buried tubers.
- A wider range of foods, which buffers against seasonal shortage — an individual with more options is less likely to starve in a lean period.
- Reduced risk. Projectile weapons allow prey to be killed at a distance, greatly reducing injury risk compared with close-quarters hunting.
- New environments became habitable, because tools allowed exploitation of resources that were otherwise inaccessible.
- Each of these means more energy and better survival, and therefore more offspring surviving to reproduce.
The use of fire
-
Evidence for controlled fire is difficult to interpret, because natural fires also leave burnt material. Convincing evidence requires hearths — repeatedly used, spatially defined burning in a location fire would not naturally reach or persist.
-
Traces appear from roughly 1 million years ago, and evidence of habitual, controlled use becomes widespread from roughly 400,000 years ago.
-
The benefits of fire, each with a distinct mechanism:
- Cooking. Heat softens food and breaks down starch and protein, so less chewing is needed and more energy is absorbed from the same material. It also kills pathogens and parasites and destroys some plant toxins, making otherwise inedible foods safe.
- Warmth, which allowed occupation of colder regions and colder seasons that would otherwise be lethal — directly enabling dispersal into higher latitudes.
- Protection from predators, since most large predators avoid fire.
- Light, which extends the active day beyond daylight hours, adding time for tool manufacture, food processing and social activity.
- Improved tool manufacture — heat treatment alters some stone so it fractures more predictably, and fire hardens wooden points.
- A social focus. A hearth gathers a group in one place for extended periods, which plausibly supported the transmission of skills and information.
-
Cooking has the largest biological consequence, because it links culture directly back to anatomy: it reduced the mechanical work of chewing, contributing to the reduction of teeth, jaws and chewing muscle attachments, and it increased energy yield, helping to make the metabolically expensive brain affordable.
Selective advantage
- Tools and fire are cultural, so they are not inherited as alleles. The selective advantage acts on the biological capacity to acquire and use them:
- Individuals better able to learn, remember and teach techniques obtained more food and survived better, so alleles supporting those cognitive abilities increased in frequency.
- Individuals whose hand anatomy allowed more accurate tool manufacture had the same advantage, which is the selection pressure behind the hand trend.
- This is why cultural and biological trends are coupled: culture creates the selection pressure that favours the biology that supports culture.
Worked Example
Worked Example
Two hominin sites are compared.
| Site P (1.6 My) | Site Q (45 ky) | |
|---|---|---|
| Stone tools | Flakes and choppers; few shaping steps | Long blades, small microliths, prepared cores |
| Other materials | None preserved | Bone points, antler harpoons, eyed needles |
| Composite tools | None | Microliths set into wooden hafts |
| Burnt material | Scattered charcoal, no defined hearths | Repeatedly used stone-lined hearths |
| Animal bones | Cut marks, some from large carcasses | Cut marks; many small fast prey species |
Describe the cultural trends shown, and explain what they indicate about cognition and about diet.
Answer:
The trends.
- Increasing complexity of manufacture. Site P has flakes and choppers requiring few steps. Site Q has prepared cores and blades, where the core is shaped first so a flake of predetermined form can be struck off.
- Increasing range of materials. Stone only at P; stone, bone and antler at Q. Bone and antler can be carved into shapes stone cannot take, such as barbed points and eyed needles.
- Increasing specialisation. General cutting edges at P; distinct tool forms for distinct jobs at Q.
- Appearance of composite tools. Microliths hafted into wooden handles at Q, absent at P.
- Controlled use of fire. Scattered charcoal at P is not sufficient evidence, since natural fires produce charcoal too. Repeatedly used stone-lined hearths at Q are strong evidence of deliberate, habitual control.
What this indicates about cognition.
Each step demands more of the maker, and the demands are specific.
- Prepared cores require the maker to work through several stages toward a product that does not yet exist. The shaped core is useless in itself; its value lies entirely in the flake it will later yield. This requires holding a goal in mind across a sequence of actions — planning in a strong sense.
- Composite tools require assembling components made separately, each useless alone — a point, a shaft, a binding. This implies planning across a longer span and an understanding of how parts combine.
- Standardised forms imply a mental template: the maker is working toward a remembered pattern rather than responding to the stone.
- Together these strongly imply teaching. Techniques of this complexity are very unlikely to be rediscovered independently by each individual, so they must be transmitted — which requires both the ability to learn from others and some means of communicating procedures.
What this indicates about diet.
- At P, cut marks including large carcasses indicate meat was processed with tools, giving access to energy-dense food.
- At Q, many small fast prey species appear. Catching such animals reliably requires projectile weapons or traps, both of which the composite tools support. This means a broader diet and less dependence on large game.
- Hearths at Q indicate cooking, which softens food and breaks down starch and protein so more energy is absorbed, and kills pathogens and parasites.
Why this matters biologically. Cooking and improved tools reduced the mechanical work of chewing, so the teeth, jaws and chewing muscle attachments were no longer maintained by selection and reduced. They simultaneously increased the energy obtained from food, helping make the metabolically expensive brain affordable. So these cultural trends are not merely parallel to the biological ones — they are among their causes.
One caution. Absence at site P is weak evidence. Wood and bone rarely preserve, so P's occupants may well have used tools of those materials that have not survived. The trend in the record is clear; the trend in actual behaviour is less sharply defined than the table suggests.