Scale: The Universal Laws of Life and Death in Organisms, Cities and Companies

by Geoffrey West

Many bacteria live for only an hour and need only a tenth of a trillionth of a watt to stay alive, whereas whales can live for over a century and metabolize at several hundred watts.

the average number of heartbeats in the lifetime of any mammal is roughly the same, even though small ones like mice live for just a few years whereas big ones like whales can live for a hundred years or more.

scaling laws provide us with a window onto underlying principles and concepts that can potentially lead to a quantitative predictive framework for addressing a host of critical questions across science and society.

Cities are the crucible of civilization, the hubs of innovation, the engines of wealth creation and centers of power, the magnets that attract creative individuals, and the stimulant for ideas, growth, and innovation.

Rapid urbanization and accelerating socioeconomic development have generated multiple global challenges ranging from climate change and its environmental impacts to incipient crises in food, energy, and water availability, public health, financial markets, and the global economy.

Despite the continuing increase in the average life span of human beings over the last 200 years, our maximum life span has remained unchanged.

No human being has ever lived for more than 123 years, and very few companies have lived for much longer—most have disappeared after 10 years.

leads to asking where all the other scales of life come from. Why, for instance, do we sleep approximately eight hours a night whereas mice sleep fifteen and elephants just four? Why are the tallest trees a few hundred feet high and not a mile?

And why are there roughly five hundred mitochondria in each of your cells?

metabolism. Quantitatively, this is expressed in terms of metabolic rate, which is the amount of energy needed per second to keep an organism alive;

for us it’s about 2,000 food calories a day, which, surprisingly, corresponds to a rate of only about 90 watts, the equivalent of a standard incandescent lightbulb.

None of these systems, whether “natural” or man-made, can operate without a continuous supply of energy and resources that have to be transformed into something “useful.” Appropriating the concept from biology, I shall refer to all such processes of energy transformation as metabolism.

Depending on the sophistication of the system, these outputs of useful energy are allocated between doing physical work and fueling maintenance, growth, and reproduction.

the major portion of our metabolic energy has been devoted to forming communities and institutions such as cities, villages, companies, and collectives, to the manufacture of an extraordinary array of artifacts, and to the creation of an astonishing litany of ideas ranging from airplanes, cell phones,...

without a continuous supply of energy and resources, not only can there be no manufacturing of any of these things but, perhaps more important, there can be no ideas...

Energy is primary. It underlies everything that we do and everything t...

There is always a price to pay when energy is processed; there is no free lunch. Because energy underlies the transformation and operation of literally everything, no system operates without consequences.

Second Law of Thermodynamics, which says that whenever energy is transformed into a useful form, it also produces “useless” energy as a degraded by-product: “unintended consequences” in the form of inaccessible

disorganized heat or unusable products a...

Whenever energy is used or processed in order to make or maintain order within a closed system, some degree of disorder is inevitable—entropy always increases.

The word entropy, by the way, is the literal Greek translation of “transformation” or “evolution.”

To maintain order and structure in an evolving system requires the continual supply and use of energy whose by-product is disorder.

The battle to combat entropy by continually having to supply more energy for growth, innovation, maintenance, and repair, which becomes increasingly more challenging as the system ages, underlies any serious discussion of aging, mortality, resilience, and sustainability, whether for organisms, companies, or societies.

Scaling simply refers, in its most elemental form, to how a system responds when its size changes.

What happens to a city or a company if its size is doubled? Or to a building, an airplane, an economy, or an animal if its size is halved? If the population of a city is doubled, does the resulting city have approximately twice as many roads, twice as much crime, and produce twice as many patents? Do the profits of a company double if its sales double, and does an animal require half as much food if its weight is halved?

essential feature of all cities, namely that social activity and economic productivity are systematically enhanced with increasing size of the population. This systematic “value-added” bonus as size increases is called increasing returns to scale by economists and social scientists, whereas physicists prefer the more sexy term superlinear scaling.

food calories a day just to stay alive without doing any activity or performing any tasks. This is called her basal metabolic rate

active metabolic rate, which includes all of the additional daily activities of living.

A profound consequence of this rule is that on a per gram basis, the larger animal (the woman in this example) is actually more efficient than the smaller one (her dog) because less energy is required to support each gram of her tissue (by about 25 percent).

systematic savings with increasing size is known as an economy of scale. Put succinctly, this states that the bigger you are, the less you need per capita (or, in the case of animals, per cell or per gram of tissue) to stay alive.

Size and scale are major determinants of the generic behavior of highly complex, evolving systems,

typical complex system is composed of myriad individual constituents or agents that once aggregated take on collective characteristics that are usually not manifested in, nor could easily be predicted from, the properties of the individual components themselves.

you are much more than the totality of your cells and, similarly, your cells are much more than the totality of all of the molecules from which they are composed.

What you think of as you—your consciousness, your personality, and your character—is a collective manifestation of the multiple interactions amon...

In a similar fashion, a city is much more than the sum of its buildings, roads, and people, a company much more than the sum of its employees and products, and an ecosystem much more than the plants and animals that inhabit

result from the nonlinear nature of the multiple feedback mechanisms embodied in the interactions between its inhabitants, their infrastructure, and the environment.

colony of ants. In a matter of days, they literally build their cities from the ground up, one grain at a time.

These remarkable edifices are constructed with multilevel networks of tunnels and chambers, ventilation systems, food storage and incubation units, all supplied by complex transportation routes.

Ant colonies are built without forethought and without the aid of any single mind or any group discussion or consultation. There is no blueprint or master plan.

thousands of ants working mindlessly in the dark moving millions of grains of earth and sand to create these impressive structures.

This feat is accomplished by each individual ant obeying just a few simple rules mediated by chemical cues and other signals, resulting in an ext...

bewildering dynamics and organization of highly complex systems have their origin in very simple rules governing the interaction between their individual constituents.

In general, then, a universal characteristic of a complex system is that the whole is greater than, and often significantly different from, the simple linear sum of its parts.

This collective outcome, in which a system manifests significantly different characteristics from those resulting from simply adding up all of the contributions of its individual constituent parts, is called an emergent behavior. It is a readily recognizable characteristic of economies, financial markets, urban communities, companies, and organisms. The important lesson that we learn from these investigations is that in many such systems there is no central control.

So, for example, in building an ant colony, no individual ant has any sense of the grand enterprise to which he is contributing.

Some ant species even go so far as to use their own bodies as building blocks to construct sophisticated structures: army ants and fire...

self-organization. It is an emergent behavior in which the constituents themselves agglomerate to form the emergent whole, as in the formation of human social groups, such as book clubs or political rallies, or your organs, which can be viewed as the self-organization of their constituent cells, or a city as a manifestation of the self-organization of its inhabitants.

One or more trends can reinforce other trends in a positive feedback loop until things swiftly spiral out of control and cross a tipping point beyond which behavior radically changes.