The Future of Evolution
I was asked to talk about the Future of Evolution. This is an enormous subject and would take a historian to do it justice. I am not a historian. I am a scientist with a smattering of knowledge about history. I prefer to talk about things I know. I shall be telling stories rather than digging deep into the sources of historical truth. I shall talk about astronomy and biology, which are easier to understand than physics. I shall use the recent history of astronomy and biology to illustrate some evolutionary themes, which may or may not be valid when extended to the future.
My approach to evolution is based on analogies between biology, astronomy and history. I begin with biology. The chief agents of biological evolution are speciation and symbiosis. In the world of biology these words have a familiar meaning. Life has evolved by a process of successive refinement and subdivision of form and function, that is to say by speciation, punctuated by a process of bringing together alien and genetically distant species into a single organism, that is to say by symbiosis. As a result of the work of Lynn Margulis and other pioneers, the formerly heretical view, that symbiosis has been the mechanism for major steps in the evolution of life, has now become orthodox. When we view the evolution of life with an ecological rather than an anatomical perspective, the importance of symbiosis relative to speciation becomes even greater.
As a physical scientist, I am struck by the fact that the borrowing of concepts from biology into astronomy is valid on two levels. One can see in the sky many analogies between astronomical and biological processes, as I shall shortly demonstrate. And one can see similar analogies between intellectual and biological processes, in the evolution and taxonomy of scientific disciplines. The evolution of the universe and the evolution of science can be described in the same language as the evolution of life.
2. Speciation and Symbiosis in the Sky
In the context of astronomy, speciation occurs by the process of symmetry-breaking. In the earliest stages of its history, the universe was hot and dense and rapidly expanding. Matter and radiation were then totally disordered and uniformly mixed. One of the greatest of all symmetry-breakings was the separation of the universe into two phases, one phase containing most of the matter and destined to condense later into galaxies and stars, the other phase containing most of the radiation and destined to become the intergalactic void. As a result of this transition, the universe lost its original spatial symmetry. Before the transition, it had the symmetry of uniform space. After the transition, it became a collection of lumps with no large-scale symmetry. The same process of symmetry-breaking was then repeated successively on smaller and smaller scales. A single lump of the first generation was a huge mass of gas, locally uniform and locally symmetrical. The local uniformity of the gas was then broken when it condensed into the second-generation lumps which we call galaxies. The gas in a local region of a galaxy cooled further until it condensed into the third-generation lumps which we call giant molecular clouds. Finally, the gas and dust in a local region of a molecular cloud condensed into the fourth-generation lumps which we call stars and planets. The universe in this way became a hierarchical assortment of lumps of various shapes and sizes.
The diversification of new forms of life on the earth is in many respects similar to the diversification of new celestial species, galaxies and dust-clouds and stars and planets, in the universe as it was before life appeared. The evolution of life fits logically into the evolution of the universe. Both in the non-living universe and on the living earth, evolution alternates between long periods of metastability and short periods of rapid change. During the periods of rapid change, old structures become unstable and divide into new structures. During the periods of metastability, the new structures are consolidated and fine-tuned while the environment to which they are adapted seems eternal. Then the environment crosses some threshold that plunges the existing structures into a new instability, and the cycle of speciation starts again.
Speciation is one of the two driving forces of evolution. The other is symbiosis. Symbiosis is the reattachment of two structures, after they have been detached from each other and have evolved along separate paths for a long time, so as to form a combined structure with behavior not seen in the separate components. Symbiosis played a fundamental role in the evolution of eucaryotic cells from procaryotes. The mitochondria and chloroplasts that are essential components of modern cells were once independent free-living creatures. They first invaded the ancestral eucaryotic cell from the outside and then became adapted to living inside. The symbiotic cell acquired a complexity of structure and function that neither component could have evolved separately. In this way symbiosis allows evolution to proceed in giant steps. A symbiotic creature can jump from simple to complicated structures much more rapidly than a creature evolving by the normal processes of mutation and speciation.
Symbiosis is as prevalent in the sky as it is in biology. Astronomers are accustomed to talking about symbiotic stars. The basic reason why symbiosis is important in astronomy is the double mode of action of gravitational forces. When gravity acts upon a uniform distribution of matter occupying a large volume of space, the first effect of gravity is to concentrate the matter into lumps separated by voids. The separated lumps differentiate and evolve separately. They become distinct species. But then, after a period of separate existence, gravity acts in a second way to bring lumps together and bind them into pairs. The binding into pairs is a sporadic process depending on chance encounters. It usually takes a long time for two lumps to be bound into a pair. But the universe has plenty of time. After a few billion years, a large fraction of objects of all sizes become bound in symbiotic systems, either in pairs or in clusters. Once they are bound together by gravity, dissipative processes bring them closer together. As they come closer together, they interact with one another more strongly and the effects of symbiosis become more striking.
From our human point of view, the most important example of astronomical symbiosis is the symbiosis of the earth and the sun. The whole system of sun and planets and satellites is a typical example of astronomical symbiosis. At the beginning, when the Solar System was formed, the sun and the earth were born with different chemical compositions and physical properties. The sun was made mainly of hydrogen and helium, the earth was made of heavier elements. The sun was physically simple, a sphere of gas heated by the burning of hydrogen and shining steadily for billions of years. The earth was physically complicated, partly liquid and partly solid, its surface frequently transformed by plate tectonics and other dynamic processes. The symbiosis of these two contrasting worlds made life possible. The earth provided chemical and environmental diversity for life to explore. The sun provided physical stability, a steady input of energy on which life could rely. The combination of the earth's variability with the sun's constancy provided the conditions in which life could evolve and prosper.
3. Tools and Concepts
The evolution of science is in many ways similar to the evolution of life and the evolution of the universe. The major events in the history of science are called scientific revolutions. There are two kinds of scientific revolutions, those driven by new concepts and those driven by new tools. These are analogous to biological revolutions driven by speciation and by symbiosis, or to astronomical revolutions driven by symmetry-breaking and by gravitational binding. When a field of science is overturned by a new concept, the revolution starts from the inside, from an internal inconsistency or contradiction within the science, and results in a rapid transition to a new way of thinking. When a field of science is overturned by new tools, the revolution starts from the outside, from tools imported from another discipline, and results in a symbiosis of the two disciplines. In both types of revolution, the final outcome is usually a new subdiscipline of science and a new species of scientist, specialized in the new ideas or in the new tools as the case may be.
Thomas Kuhn in his famous book, The Structure of Scientific Revolutions, talked almost exclusively about concepts and hardly at all about tools. His idea of a scientific revolution is based on a single example, the revolution in theoretical physics that occurred in the 1920s with the advent of quantum mechanics. This was a prime example of a concept-driven revolution. Kuhn's book was so brilliantly written that it became an instant classic. It misled a whole generation of students and historians of science into believing that all scientific revolutions are concept-driven. The concept-driven revolutions are the ones that attract the most attention and have the greatest impact on the public awareness of science, but in fact they are comparatively rare. In the last five hundred years we have had five major concept-driven revolutions, associated with the names of Copernicus, Newton, Darwin, Einstein and Freud, besides the quantum- mechanical revolution that Kuhn took as his model. During the same period there have been about twenty tool-driven revolutions, not so impressive to the general public but of equal importance to the progress of science. I will not attempt to make a complete list of tool-driven revolutions. Two prime examples are the Galilean revolution resulting from the use of the telescope in astronomy, and the Crick-Watson revolution resulting from the use of X-ray diffraction to determine the structure of big molecules in biology. Galileo brought into astronomy tools borrowed from the emerging technology of eye-glasses. Crick and Watson brought into biology tools borrowed from physics. The effect of a concept-driven revolution is to explain old things in new ways. The effect of a tool-driven revolution is to discover new things that have to be explained. In astronomy there has been a preponderance of tool-driven revolutions. We have been more successful in discovering new things than in explaining old ones.
4. The Domestication of Biotechnology
Up to this point, I have been talking about evolution that has happened in the past. From this point on I will talk about evolution that may happen in the future. I will be telling stories about the future. I have three stories to tell. One of them is about a prediction that turned out to be wrong. The other two are about predictions that might be right and might be wrong. The moral of the stories is, life is a game of chance, and science is like life. Most of the time, science cannot tell what is going to happen.
My first story is about the domestication of biotechnology. Fifty years ago in Princeton, I watched the mathematician John von Neumann designing and building the first electronic computer that operated with instructions coded into the machine. Von Neumann did not invent the electronic computer. The computer called ENIAC had been running at the University of Pennsylvania five years earlier. What von Neumann invented was software, the coded instructions that gave the computer agility and flexibility. It was the combination of electronic hardware with punch-card software that allowed a single machine to predict weather, to simulate the evolution of populations of living creatures, and to test the feasibility of hydrogen bombs. Von Neumann understood that his invention would change the world. He understood that the descendants of his machine would dominate the operations of science and business and government. But he imagined computers always remaining large and expensive. He imagined them as centralized facilities serving large research laboratories or large industries. He failed to foresee computers growing small enough and cheap enough to be used by housewives for doing income-tax returns or by kids for doing homework. He failed to foresee the final domestication of computers as toys for three-year-olds. He totally failed to foresee the emergence of computer-games as a dominant feature of twenty-first-century life. Because of computer-games, our grandchildren are now growing up with an indelible addiction to computers. For better or for worse, in sickness or in health, till death do us part, humans and computers are now joined together more durably than husbands and wives.
What has this story of von Neumann's computer and the evolution of computer-games to do with biotechnology? Simply this, that there is a close analogy between von Neumann's vision of computers as large centralized facilities and the public perception of genetic engineering today as an activity of large pharmaceutical and agribusiness corporations such as Monsanto. The public distrusts Monsanto because Monsanto likes to put genes for poisonous pesticides into food-crops, just as we distrusted von Neumann because von Neumann liked to use his computer for designing hydrogen bombs. It is likely that genetic engineering will remain unpopular and controversial so long as it remains a centralized activity in the hands of large corporations.
I see a bright future for the biotech industry when it follows the path of the computer industry, the path that von Neumann failed to foresee, becoming small and domesticated rather than big and centralized. The first step in this direction was already taken recently, when genetically modified tropical fish with new and brilliant colors appeared in pet-stores. For biotechnology to become domesticated, the next step is to become user-friendly. I recently spent a happy day at the Philadelphia Flower Show, the biggest flower show in the world, where flower-breeders from all over the world show off the results of their efforts. I have also visited the Reptile Show in San Diego, an equally impressive show displaying the work of another set of breeders. Philadelphia excels in orchids and roses, San Diego excels in lizards and snakes. The main problem for a grandparent visiting the reptile show with a grandchild is to get the grandchild out of the building without actually buying a snake. Every orchid or rose or lizard or snake is the work of a dedicated and skilled breeder. There are thousands of people, amateurs and professionals, who devote their lives to this business. Now imagine what will happen when the tools of genetic engineering become accessible to these people. There will be do-it-yourself kits for gardeners who will use genetic engineering to breed new varieties of roses and orchids. Also kits for lovers of pigeons and parrots and lizards and snakes, to breed new varieties of pets. Breeders of dogs and cats will have their kits too.
Genetic engineering, once it gets into the hands of housewives and children, will give us an explosion of diversity of new living creatures, rather than the monoculture crops that the big corporations prefer. New lineages will proliferate to replace thosethat monoculture farming and industrial development havedestroyed. Designing genomes will be a personal thing, a new art-form as creative as painting or sculpture. Few of the new creations will be masterpieces, but all will bring joy to their creators and variety to our fauna and flora.
The final step in the domestication of biotechnology will be biotech games, designed like computer games for children down to kindergarten age, but played with real eggs and seeds rather than with images on a screen. Playing such games, kids will acquire an intimate feeling for the organisms that they are growing. The winner could be the kid whose seed grows the prickliest cactus, or the kid whose egg hatches the cutest dinosaur. These games will be messy and possibly dangerous. Rules and regulations will be needed to make sure that our kids do not endanger themselves and others.
If domestication of biotechnology is the wave of the future, five important questions need to be answered. First, can it be stopped? Second, ought it to be stopped? Third, if stopping it is either impossible or undesirable, what are the appropriate limits that our society must impose on it? Fourth, how should the limits be decided? Fifth, how should the limits be enforced, nationally and internationally? In considering each of these questions, it would be helpful to keep in mind the analogy between computer technology and biotechnology. The majority of people using domesticated biotechnology to cause trouble will probably be small fry, like the young computer hackers who spread computer viruses around on the internet. Young people possessing bio-hacker skills may also be helpful in tracing and reporting any larger-scale illegitimate activities to national or international authorities. In the long run, as biotechnology spreads over the world, our best chance of avoiding large-scale bioterrorism will be to share the benefits of biotechnology as widely and as openly as possible.
5. The Darwinian Interlude
My second story was suggested by Carl Woese, the world's greatest expert in the field of microbial taxonomy. He explored the ancestry of microbes by tracing the similarities and differences between their genomes. He discovered the large-scale structure of the tree of life, with all living creatures descended from three primordial branches. He recently published a provocative and illuminating article with the title, "A New Biology for a New Century.'' It appeared in the June 2004 issue of Microbiology and Molecular Biology Reviews. His main theme is the obsolescence of reductionist biology as it has been practiced for the last hundred years, and the need for a new synthetic biology based on communities and eco-systems rather than on genes and molecules. He does not mention Teilhard de Chardin, but he is clearly echoing Teilhard's ideas. Aside from his main theme, he raises another profoundly important question: When did Darwinian evolution begin? By Darwinian evolution he means evolution as Darwin understood it, based on the competition for survival of non-interbreeding species. He presents evidence that Darwinian evolution did not go back to the beginning of life. The comparison of genomes of ancient lineages of living creatures shows evidence of massive transfers of genetic information from one lineage to another. In early times, the process that he calls Horizontal Gene Transfer, the sharing of genes between unrelated species, was prevalent. It becomes more prevalent, the further back you go in time.
Whatever Carl Woese writes, even in a speculative vein, needs to be taken seriously. In his "New Biology'' article, he is postulating a golden age of pre-Darwinian life, when horizontal gene transfer was universal and separate species did not exist. Life was then a community of cells of various kinds, sharing their genetic information so that clever chemical tricks and catalytic processes invented by one creature could be inherited by all of them. Evolution was a communal affair, the whole community advancing in metabolic and reproductive efficiency as the genes of the most efficient cells were shared. Evolution could be rapid, as new chemical devices could be evolved simultaneously by cells of different kinds working in parallel and then reassembled in a single cell by horizontal gene transfer. But then, one evil day, a cell resembling a primitive bacterium happened to find itself one jump ahead of its neighbors in efficiency. That cell, anticipating Bill Gates by three billion years, separated itself from the community and refused to share. Its offspring became the first species, reserving its intellectual property for its own private use. With its superior efficiency it continued to prosper and to evolve separately, while the rest of the community continued its communal life. Some millions of years later, another cell separated itself from the community and became another species. And so it went on, until nothing was left of the community and all life was divided into species. The Darwinian interlude had begun.
The Darwinian interlude has lasted for two or three billion years. It probably slowed down the pace of evolution considerably. The basic biochemical machinery of life had evolved rapidly duringthe few hundreds of millions of years of the pre-Darwinian era, and changed very little in the next two billion years of microbial evolution. Darwinian evolution is slow because individual species once established evolve very little. Darwinian evolution requires established species to die and become extinct so that new species can replace them. Three innovations helped to speed up the pace of evolution in the later stages ofthe Darwinian interlude. The first was sex, which is a form of horizontal gene transfer restricted to operating within species. The second innovation was multicellular organization, which opened up a whole new world of form and function. The third was brains, which opened another new world of coordinated sensation and action, culminating in the evolution of eyes and hands. Allthrough the Darwinian interlude, occasional mass extinctions due to volcanic outbursts or asteroid impacts helped to open opportunities for new evolutionary ventures.
Now, after three billion years, the Darwinian interlude is over. It was an interlude between two periods of horizontal gene transfer. The epoch of Darwinian evolution based on competition between species ended about ten thousand years ago when a single species, Homo Sapiens, began to dominate and reorganize the biosphere. Since that time, cultural evolution has replaced biological evolution as the main driving force of change. Here Carl Woese is again echoing Teilhard. Cultural evolution is not Darwinian. Cultures spread by horizontal transfer of ideas more than by genetic inheritance. Cultural evolution is running a thousand times faster than Darwinian evolution, taking us into a new era of cultural interdependence which we call globalization. And now, in the last thirty years, Homo Sapiens has revived the ancient pre-Darwinian practice of horizontal gene transfer, moving genes easily from microbes to plants and animals, blurring the boundaries between species. We are moving rapidly into the post-Darwinian era, when species will no longer exist, and the evolution of life will again be communal. If you like, you can call that the evolution of a noosphere. That is the end of my second story.
6. Bad Advice to a Young Scientist
My last story is about a prediction that I made almost sixty years ago, when I was young and arrogant. It is an extreme example of wrongness, perhaps a world record in the category of wrong predictions. The story is about Francis Crick, the great biologist who died a few months ago after a long and brilliant career. He discovered, with Jim Watson, the double helix. They discovered the double helix structure of DNA in 1953, and thereby gave birth to the new science of molecular genetics. Eight years before that, in 1945, before World War II came to an end, I met Francis Crick for the first time. He was in Fanum House, a dismal office building in London where the Royal Navy kept a staff of scientists. Crick had been working for the Royal Navy for a long time and was depressed and discouraged. He said he had missed his chance of ever amounting to anything as a scientist. Before World War II, he had started a promising career as a physicist. But then the war hit him at the worst time, putting a stop to his work in physics and keeping him away from science for six years. The six best years of his life, squandered on naval intelligence, lost and gone forever. Crick was good at naval intelligence, and did important work for the navy. But military intelligence bears the same relation to intelligence as military music bears to music. After six years doing this kind of intelligence, it was far too late for Crick to start all over again as a student and relearn all the stuff he had forgotten. No wonder he was depressed. I came away from Fanum House thinking, "How sad. Such a bright chap. If it hadn't been for the war, he would probably have been quite a good scientist.''
A year later, I met Crick again. The war was over and he was much more cheerful. He said he was thinking of giving up physics and making a completely fresh start as a biologist. He said the most exciting science for the next twenty years would be in biology and not in physics. I was then twenty-two years old and very sure of myself. I said, "No, you're wrong. In the long run biology will be more exciting, but not yet. The next twenty years will still belong to physics. If you switch to biology now, you will be too old to do the exciting stuff when biology finally takes off'." Fortunately, he didn't listen to me. He went to Cambridge and began thinking about DNA. It took him only seven years to prove me wrong. The moral of this story is clear. Even a smart twenty-two-year-old is not a reliable guide to the future of science. And the twenty-two-year-old has become even less reliable now that he is eighty-one.
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