A Geoffrey West (Taunton, England, 1940) likes to walk the frontiers of knowledge. Since the beginning of his career, this theoretical physicist has dreamed of being part of a community of scientists interested in big questions, and he has finally found his Ithaca at the Santa Fe Institute, in New Mexico (USA), which he now chairs. There he has surrounded himself with experts in different areas who collaborate to solve enigmas at all levels, from the structure of the cell to the secrets of the cosmos. They all have in common that they arecomplex systems, a concept of physics that West has used in biological and social contexts with surprising results.
In the mid-1990s, when he was leading the group of elementary particles at the Los Alamos National Laboratory, he set out to study with quantitative methods the most complex of all phenomena: life. Since then his work has shed light on problems as diverse as they are fundamental: evolution, urban dynamics, aging, environment … In 2006 the magazineTime included him among the hundred most influential personalities of the moment. For something they call him“the Master of Complexity”.
-What is a complex system?
-It is difficult to condense the idea into a few sentences. It reminds me of what someone said in the US Supreme Court about pornography: “I can’t define it, but I know when I’m looking at it.” A complex system is composed of many elements that are related by means of simple rules, and these interactions produce emergent phenomena: the whole is more than the sum of the parts. For example, a city is much more than the grouping of its inhabitants; it has its own dynamic that arises from the relationships between them. Another characteristic of a complex system is that it depends on its history and its context: if you were born in the United States, you would be someone else.
-From theoretical physics to biological and social complexity … Why this change in your career?
-I am still passionate about the most exciting challenges in physics, such as elementary particles, the laws of nature, but I am also interested in the origin and structure of life, which are just as important or more. I want to know if there are principles from which I can extract a quantitative and mathematical theory of life. In the last ten years I have proven the power of theoretical physics to solve problems in biology, economics, society and sustainability.
-What tool allows you to treat such diverse fields?
-When I started working in biology, the first thing I did was apply ideas from physics, such as the laws of scale, to discover the dynamics of a living system. I wanted to find out to what extent a large animal is like a small one, but on a large scale. I set about choosing specific characteristics and seeing how they changed with the size of the organism. Together with biologists James Brown and Brian Enquist I studied the metabolic rate, which is the energy per unit of time that a living being needs to maintain itself. For a human the rate is about 2,000 kilocalories per day. And for a mammal of another size? Interestingly, it follows a very strict law: the metabolic rate grows with the exponent 3/4 of its mass. In other words: if you increase the mass of the animal 10,000 times, the rate is multiplied by only 1,000. That reveals an economy of scale in nature: the bigger you are, the less energy you need to maintain your tissues. It’s amazing! We can look at another variable, like the length of the aorta, or deeper things, like the rate of growth; any biological phenomenon obeys a law with the exponent 1/4. 4 is the universal number of life! The surprising thing is that, when dealing with the most complex phenomena that exist, the laws are very simple and, in addition, the same for different living beings, each with its evolutionary history.
-How do you explain something like that?
-The idea is that universality and simplicity arise from solving the main problem faced by a biological system: ensuring the maintenance of each of its components. Natural selection has solved this through networks. We are a handful of interconnections: the nervous system, the bones, the cells themselves, all are made up of hierarchical and branched networks. And the constraints that organisms adapted to in their evolution affected their networks, not individual elements.
-So, according to this vision, life is controlled by networks.
-That is the idea, and its properties must be independent of the design of each individual. The first property is that the networks fill the entire space: each cell is oxygenated by blood through capillaries that reach everywhere. The second property is that the constituent units of the network remain unchanged in the group: the capillaries of all mammals are equal. The third point is the most powerful: natural selection has optimized the performance of networks. The cardiovascular system that we share goats, humans and lions uses the least amount of energy possible, and thus we can use it in biologically valuable tasks, such as having children.
-So much uniformity collides with the diversity of nature.
-There’s the key! Natural selection has not reinvented the building blocks of organisms: not cells, not capillaries, not mitochondria. Think about electrical grids. The AC / DC converter in this building is the same as the one in your house, mine or in Bangladesh. Its architecture is different, but its basic elements do not change. If we double the size of the building, that of each outlet is not doubled. Similarly, my flesh and cells are like those of a mouse, but not like those of a spider, because “biological scaling” works within the same taxonomic group. The whale has fins, the elephant trunk and the giraffe a very long neck, but these differences are irrelevant, they only depend on the specific environment.
-How are these ideas used to study social systems?
-We use laws of scale that come from millions of measurements made over years, and we look for the dynamics and universal principles that underlie organizational structures. That is our framework, valid at all levels: molecular, cellular, social … We can apply it to many problems: cancer, evolution, ecosystems, aging, etc. For example, the case of cities is exciting. Since 2007 most of the planet’s population lives in cities and in 2050 the figure will be 80%. The Earth is urbanizing, and all global problems – heat, pollution, disease, crime, accidents – originate in the city. The irony is that cities are also the source of solutions, because the people who create and invent live in them. And the amazing thing is that there is no theory of cities. I am not referring to a qualitative study. For me, a theory is a bunch of principles, a mathematical framework in which you can model, quantify, and understand a problem, just like it’s done in physics. Science must be the tool.
-Cities are perhaps the most complex systems, aren’t they?
-That’s why it’s so exciting trying to understand how they work. In recent years I have applied laws of scale to see if cities follow their own dynamics. A dog is a huge mouse. And Madrid is Toledo on a large scale? Perhaps they consist basically of the same thing, and their differences – one is modern, another historical – are only details.
-How do you study cities?
-Analyzing everything that can be taken into account: salaries, roads, restaurants, hospitals, cars, universities, schools, patents generated, etc. For this I have brought together at the Santa Fe Institute a group of experts in economics, geography, anthropology, physics … You cannot tackle a problem without experts from various disciplines, and most importantly, they must interact in a productive way.
-What do you mean?
-That an anthropologist and a physicist speak different languages. They may even disagree on what science is. Getting them to collaborate efficiently is a big challenge. When I started working with biologists, I found that the only way it worked was to meet every week for a whole morning. It requires a tremendous commitment, like that of a relationship. And still there are fights. Sometimes I come home after the meeting thinking, “oh my gosh, they haven’t understood anything.”
-What is the philosophy of the Santa Fe Institute?
-We always undertake projects with great ideas and extraordinary people. In today’s academic landscape, everyone works in highly specialized and narrow fields. We are looking for well-educated people who think big, take risks and dare to work in multidisciplinary lines: a physicist interested in economics or a biologist interested in anthropology. But today the scientific system – publications, funding – forces us to follow a straight line and thus the big questions are lost. If you want to be the world’s expert on a tiny bit of something, you might win the Nobel, but we’re not interested in you. If you are willing to explore an idea in a broad context without being constrained by your own discipline, you are what we want.
-Is it a Leonardos factory?
-It’s what we would like! As a young man he had a romantic image of the university as a community of scholars. The reality is not like that: you do your job, period. And at the end of my career I have found the place I have been looking for for 40 years.
-A place where huge theoretical puzzles are solved.
-Exactly. And when solving them we discover that simplicity is hidden under the most complex, that is why I believe that our vision is powerful. When you look at biology, everything is so complicated that you think: “by God, I can’t study every case!” Biologists and social scientists are dominated by diversity and think that everything is a special case. “You’re always simplifying,” they tell me. A physicist is trained just for that. Who would think that Newton’s three laws govern everything? And then come quantum mechanics and relativity and it turns out that our brains are governed by the same laws as the cars that go down the street. Amazing! That is the kind of thinking that guided Galileo or Newton, who revolutionized the way we understand the world.
-In other words, physicists need to put a bit of order.
-Of course, we look for the theory about the Everything, and the others only do … engineering! It’s a joke. I am interested in problems at all scales: life, society or the universe. Physics should be the study of fundamental questions in a quantitative framework. Physicists ask about the great mysteries. For example, why is mathematics the language of nature? It is an incredibly beautiful enigma.
-Does presiding over the Santa Fe Institute leave you time to investigate?
-No, but I insist on continuing to do so and I am going to suffer a psychotic break at any moment. I am living my fifth life crisis, which is my first as an old man. I hope I am not still alive when the next ones arrive!
Esperanza Garcia Molina
