Book Summary: “Unbound: How Eight Technologies Made Us Human” by Richard L. Currier

Book Review

Title: Unbound: How Eight Technologies Made Us Human and Brought Our World to the Brink
Author: Richard L. Currier
Scope: 5 stars
Readability 4.5 stars
My personal rating: 5 stars
See more on my book rating system.

Topic of Book

Connection between technologies and human history.

Important Quotes from book

Over the course of the last five million years, eight key technologies have profoundly altered the relationship of our species with the natural environment, liberating us from the natural forces that restrain the populations of all other living things.

My goal in writing this book has been to identify the fundamental biological and cultural transformations—and the technologies which triggered them—by which, step by step, the human species has arrived at our present exalted yet precarious state of being. 

The Primate Baseline

Group solidarity and the concept of a homeland; the social bonds forged by motherhood, sex, friendship, and social hierarchies; the flexibility of the fission-fusion society; the advantages of exogamy; and the rudiments of hunting, warfare, tools, weapons, customs, and traditions all exist among non-human primates. These are the genetic building blocks of human behavior. Without them, human society would have never evolved, and the world we live in would have never come into being.

Spears and Digging Sticks:

It was the technology of wooden spears and digging sticks—an innovation that must have begun with prehistoric apes ancestral to the hominids—that provided the survival advantages that were great enough to produce an evolution into full upright posture and true bipedal locomotion. 

Once the early hominids adopted a technology that included tools and weapons made of wood, they began to use their lethal weapons for hunting and killing other animals for meat. In doing so, they created a uniquely human ecological adaptation—a way of life known as hunting and gathering.

Hominids are the only animal species in which the males are predators, the females are foragers, and both sexes regularly share the different foods they obtain.

Male hominids have developed a pattern of sexual behavior that also appears to be unique among group-living primates. The typical adult male hominid is strongly bonded to a single female consort who is sexually available most of the time—the sexual pattern we call monogamy.

As the object of both maternal and sexual bonds, the female hominid became the emotional anchor of a social institution that had never before existed among group-living primates: the permanent nuclear family of mother, father, and offspring.

The hominid pattern of monogamy also created a new role in primate society: the role of the father, bonded to a single female and her offspring. 

The hominid family is more than a strategy for survival; it is the bedrock of human society.

When the ancestors of the hominids began to make, carry, and use spears and digging sticks in their daily lives, they set in motion a cascade of events that culminated in the evolution of an animal with a radically new physical form, an adaptation to the environment that required unprecedented cooperation between males and females, a huge expansion of sexual behavior, and the emergence of family ties that would provide the building blocks for the larger and more advanced societies of modern humans.


But of all the species in the animal kingdom, only the hominids have ever exhibited even the most rudimentary ability to make, control, or employ the use of fire as a regular feature of its daily life.

If it were not for their unique bipedal anatomy, hominids would have never been able to control and use fire.

The ability to control fire conferred numerous benefits to the emerging humans. Fire not only drove large and dangerous predators out of the caves—it also drove out the insects, reptiles, and disease-carrying vermin that also inhabited the caves. And by setting fire to an area covered in dense brush, the harmful insects, reptiles, and poisonous snakes that lived in these habitats could be killed or driven out of fairly large areas. Setting fire to the thickets of brush in the savannah environment also tended to clear the land, promoting the growth of tender new grasses and attracting the grazing animals.

Fire provided a controllable source of heat that not only rendered the cold, damp interiors of caves more habitable but also allowed the emerging humans to migrate into colder climates… Lastly, fire allowed the emerging humans to develop advanced tool-making techniques. These included the deliberate tempering or hardening of wooden tools and weapons.

And without doubt the most important of these uses—with consequences that reached far beyond the needs of the moment to profoundly shape the future of human evolution itself—was the discovery of cooking.

Furthermore, the brain is not the only “expensive tissue” in the body. Other tissues with similarly high energy demands include the heart, liver, kidneys, and digestive organs. Taken together, the brain and these vital organs make up less than 7 percent of the body’s weight, yet, when the body is in a resting state, they consume an astounding 60 to 70 percent of its available energy.

This leaves the digestive organs as the only candidates available for reduction in size and energy requirements. It is not surprising, then, to find that the human digestive organs—particularly the stomach and intestines—are the smallest, relative to body weight, of all the primates.

This massive increase in the size of the brain in the space of two million years is unprecedented in the evolution of life on Earth.

None of the ways that humans interact with fire—carrying burning torches from one place to another, blowing on hot embers to light kindling, roasting meat and vegetable foods, feeding a campfire with fresh firewood, and holding the arms and legs out over a fire to warm them—would be possible if we had retained the long hairy fur that covers the bodies of all other primate species.

The technology of fire was, in fact, the singular achievement by which the emerging humans crossed—decisively and irrevocably—the immense gulf that has separated humanity from the rest of the animal kingdom ever since.

Clothing and Shelter:

There is little precedent for the wearing of clothing by any animal species except hominids. Along with the controlled use of fire, the invention of clothing by hominids ranks as one of the singular achievements that distinguishes us from all other forms of animal life.

Symbolic Communication:

By replacing the slow process of biological evolution with the fast process of cultural evolution, the technology of symbolic communication allowed the anatomically modern humans to respond quickly and easily to the changing climates of the past fifty thousand years.

Only humans are free to invent countless thousands of visual and vocal symbols for the purpose of communication. And only humans are able to transmit these invented symbols to their offspring—and to other members of the group—entirely through the processes of teaching, learning, and imitation.

It is important to note that while the capacity for learning and creating symbols resides in the DNA of anatomically modern humans, the form and meaning of the symbols invented by modern humans is entirely cultural and has no basis in biology.

A new kind of behavior may originate with a single individual and be rapidly transmitted to other individuals through learning and imitation. If this new behavior helps the individual to adapt more successfully to his or her environment, it can spread easily throughout an entire social group within the space of a single generation.

New behaviors can spread not only within a single social group but also from one social group to another—and in this fashion ultimately spread throughout the population of an entire geographical region. Finally, cultural innovations rarely originate as random events. Unlike genetic mutations, the changes in behavior that drive cultural evolution are usually purposeful and deliberate, and for that reason they are much more likely to be beneficial and adaptive than the mutations that drive biological evolution.


But when the Paleolithic era came to an end with the waning of the last major ice age, humanity freed itself of the need—which limits and circumscribes the lives of all other animals—to be perpetually engaged in the search for something to eat.

When humans developed fully elaborated languages, all of the detailed knowledge about the life cycles and behavior of the plants and animals in a society’s environment—which had previously been limited to the knowledge that a single individual could amass in a single lifetime—became the accumulated wisdom of entire cultures. 

Instead of differences in wealth being based on the difference between older and younger siblings—as was typical of the people of the Northwest Coast—differences in wealth among agricultural societies gradually became the privilege of entire families and was inherited from parents to offspring. These inherited differences in wealth and status ultimately led to the formation of permanent social classes and to the evolution of “stratified” societies.

As organized hunting by groups of males for large game became less and less important as an economic necessity, organized warfare by males for the land, material wealth, and women of other agricultural villages and rival tribes became an increasingly attractive strategy for acquiring wealth, property, and descendants.

As a general rule, the larger and the more permanent the agricultural settlements became, they more devastating was their practice of warfare… The ancient urban civilizations all organized standing armies, and warfare became a strategy of conquest, carried out on a large scale, for the purpose of dominating and controlling ever larger areas of land and ever larger numbers of people.

Ships, Writing, Wheel:

The ancient cities were the first human settlements composed mainly of people who were free from the need to find or produce food, and the ancient civilizations were the first human societies in which large numbers of complete strangers were free to interact in an atmosphere of safety and confidence. These were entirely new developments in the history of human society. 

Some of the Neolithic villagers began to make things which they could trade for the surplus food produced by others. For the first time in human history, numerous members of the human group became liberated from the need to endlessly hunt for and gather food, and the division of labor we call “craft specialization” was born.

This division of society between relatively impoverished and powerless farmers on the one hand and much wealthier and more powerful city dwellers on the other became a feature of every urban civilization in ancient times.

The emergence of urban civilization seems to have happened virtually overnight, with numerous cities springing up all over the ancient world in the space of just a few centuries before and after the year 3000 BC.

This rapid and dramatic transformation in human life occurred when several factors—including population density, the favorable geography of river valleys, craft specialization, and innovations in the technologies of transportation and communication—combined to produce a volatile and unstable condition known as a “positive feedback loop,” which can cause major changes to take place in unusually short periods of time.

It has been estimated that roughly 85 percent of the population of all civilized societies throughout history consisted of agricultural food producers, while the remaining 15 percent consisted of the urban professionals who made civilized society possible. 

Precision Machinery: Clocks, Engines and Industrial Society

Sometime between 1200 and 1300 AD, in response to the Church’s desire for more accurate clocks, the craftsmen of medieval Europe began to build mechanical clocks out of metal.

By far the most important consequence of the European obsession with time was that the construction of accurate clocks required machines that were capable of making precisely crafted mechanical components.

Driven both by the clockmakers’ need for precision machinery and the public’s increasing demand for mechanical clocks, the European craftsmen began to invent the special devices called “machine tools”—which are machines designed to make parts for other machines. 

Gutenberg’s combination of movable type, oil-based ink, and the precision-built screw press unleashed an explosive growth in printed material. Before long, the huge expansion of knowledge made possible by the flood of cheap and plentiful books and pamphlets that issued from the printing presses of Europe was a major cause of the intellectual awakening of the Renaissance.

The impact of Watt’s success at creating a steam engine that delivered rotary power at relatively high speeds cannot be overstated. It liberated European society from its age-old dependence on water wheels—which could only be placed in favorable locations where a reliable source of falling water could be harnessed—as well as on windmills, which were dependent on the unpredictable coming and going of favorable winds. For the first time, a source of rotary power could be located wherever it was most advantageous.  

Of all the consequences that flowed from the creation of an efficient steam engine with rotary power, none was greater than its enormous impact on the means of transportation by land and by sea. When the steam engine was attached to a huge wheel fitted with wooden paddles, the steamship was born. When the steam engine was mounted on a large and heavy wagon made entirely of steel and placed on steel rails, the railroad was born. And of all the many offspring of the rotary steam engine, the steamship and the railroad had to be counted among the most transformative. Together, they revolutionized long-distance travel and trade.

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