The biological importance of memory

It is not brains that make memories; it is people, who use their brains to do so. And animals, non-human animals, also make memories, and can learn and change their behaviour as a result of experience. Even some animals without much in the way of brains at all, just rather basic nervous systems, can do it. What this points to is the tremendous importance that the capacity to learn and remember has for the survival of animals. Plants do not need nervous systems, because all they have to do is to stand around with their arms – or branches – spread wide so that their leaves can catch the sun and photosynthesize. But animals which live on plants, and even more so animals which live on other animals, have to use their wits to find and capture their prey, and to avoid being eaten in their turn at least long enough to be able to reproduce. Such ways of making a living in the world demand the development of sensitive sense organs, and the capacity to register and interpret the data provided by those sense organs, to compare it with past experience and, even more, with the outcomes of that past experience. And this is what learning and memory are all about. It is not the only route to evolutionary success. After all, bacteria do pretty well without either brains or nervous systems, or even much by way of memory – though there have been some disputed claims that they can learn from experience.

I read somewhere that writers, or perhaps all artists, are haunted or hunted by unusually vivid memories of their early lives – as are the old, whose useful daily memories are decaying. Certainly I remember being obsessed as a child by a kind of ‘glittering’ quality about certain experiences, usually without deep importance in what I thought of as the narrative of my life – experiences excessively bright, strongly outlined, recognized so to speak as important, even when they were met for the first time. (Re-cognizedimplies memory, the existence of a former cognition.) It is not too much to say that these experiences were as tormenting as they were delightful, until I, the person who underwent them, formed the project of being a writer – because only the act of writing gave them a glimmer of the importance they had in life, and thus gave them a place, a form and an order which made sense of them. And which they seemed to ask for. Proust, at the beginning of À la Recherche du Temps Perdu, speaks of certain experiences which forced him to look at them – ‘a cloud, a triangle, a belltower, a flower, a pebble’ – and gave him, as a child, a sense of duty towards them, a feeling that they were a symbolic language which he ought to decipher.

Darwin's legacy

Charles Darwin is most famous as a natural historian, but his work had a profound influence on our understanding of memory because of his conception of biological time. Darwin set biology in a much longer context of time than had previous religious versions of creation and biological history, and so he created a puzzle: what is the relation of natural time, measured in millions of years, to the human historical time-frame in which we measure, say, the growth of classes or the development of cities in decades and centuries? Historical time seems a mere blip on the evolutionary scale. As the psychologist William James noted, our personal experiences of time are even more inconsequential in the Darwinian scheme of things, since personal events usually span mere days and months.

Moreover, Darwin gave natural time a distinctive character: he depicted it as conflictual and competitive. The concept of the survival of the fittest came late in Darwin's thinking, and he was ambivalent about the idea. He did not, like Alfred, Lord Tennyson, imagine nature ‘red in tooth and claw’, but he did think that what we call today an ecosystem depended on the ever-changing strengths and weaknesses of the species it contained, and that extinction and species failure were part of this natural order. Time is a destroyer as well as a creator.

In April 1991 ‘Cadbury World’ was opened by the then Prime Minister, John Major, in the multiracial city of Birmingham, England. ‘Cadbury World’ is a living museum, the museum of Cadbury, the celebrated Quaker family who established a world famous cocoa and chocolate business and made their name a household name. ‘Cadbury World’ replaced the factory tours and educational visits which Cadbury provided until 1970 on the Bournville site. After the factory was closed to visitors the firm received thousands of requests for information and finally decided to construct a purpose-built ‘experience’ – the chocolate experience – next to the factory. This chocolate theme park attracts half a million visitors a year. It combines an exhibition with a brief factory tour. It aims, in the words of the accompanying brochure, to ‘reflect the heritage of the UK's number one chocolate company‘.

It tells the story of Cadbury, the Quaker family firm which began in the 1830s as a small retail business in Bull Street, Birmingham, went through difficult times in the 1850s but by dint of the hard work of two Cadbury brothers was successful enough in the 1870s to warrant the purchase of extensive land in Bournville and build the ‘factory in the garden’, which became famous the world over. There the large modern factory was combined with a model village and community facilities to provide a whole way of life for Cadbury employees.

Analogies

I was asked to write about the ‘Evolution of Science’. 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 write about things I know. Here, I tell stories rather than digging deep into the sources of historical truth. I write about astronomy, which is one little corner of science, and about recent events with which I am familiar. I use the recent history of astronomy to illustrate some evolutionary themes, which may or may not be valid when extended to earlier periods or to other areas of science.

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, i.e. symbiosis. As a result of the work of the biologist 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.

If evolution is the process of cumulative change then cities can be characterized as metabolisms that adapt over time in order to survive. In this chapter I argue that London, like other complex urban systems, is a fragile and delicate structure that has come full circle in the cycle of evolutionary change. The city is now facing an environmental, social and political crisis that threatens its very existence. Its future cannot be left to processes of random mutation, where market forces determine the policies and shape of its physical fabric. Intelligent forward planning, anticipatory design and government intervention are necessary to avoid the process of gradual decline and eventual extinction that has affected urban cultures in the past.

As the magnitude of the global environmental crisis comes to light, the design and management of our cities (the major consumers of world energy and producers of pollution) are becoming more critical to the survival of the planet. The solution lies in cities such as London becoming sustainable – circular metabolisms that conserve resources, use renewable energies and recycle waste, providing an equitable and stable social environment for future generations.

Sustainable growth

London is not alone in the struggle for urban survival. Human life has always depended on three variables: population, resources and environment. Today, we are the first generation of human inhabitants of the planet to face and be aware of the simultaneous impact of expanding populations, depletion of resources and erosion of the environment. All this is common knowledge, and yet, industrial expansion and urban growth carries on regardless.

This chapter sets itself the modest task of explaining the broad pattern of history on all the continents for the last 13 000 years. Why did history take such different courses for peoples of different continents?

Eurasians, especially peoples of Europe and eastern Asia, have spread around the globe. They and their overseas descendants now dominate the modern world in wealth and power. Other peoples, including most Africans, survived and have thrown off European domination but remain far behind in wealth and power. Still other peoples, including the original inhabitants of Australia, the Americas and southern Africa, are no longer masters of their own lands but have been decimated, subjugated and even exterminated by European colonialists. Why did history turn out that way, instead of the opposite way? Why were American Indians, Africans and Aboriginal Australians not the ones who conquered or exterminated Europeans and Asians?

This question can easily be pushed back one step further. By the year A.D. 1500, the approximate year when Europe's overseas expansion was just beginning, peoples of the different continents already differed greatly in technology and political organization. Much of Eurasia and North Africa was occupied by Iron Age states and empires, some of them on the verge of industrialization. Two Native American peoples, the Incas and Aztecs, ruled over Stone Age or nearly Bronze Age empires. Parts of sub-Saharan Africa were divided among small indigenous Iron Age states or chiefdoms. All peoples of Australia, New Guinea and the Pacific Islands, and many peoples of the Americas and sub-Saharan Africa, lived as Stone Age farmers or hunter–gatherers.

It seemed at first paradoxical to find myself invited to write about ‘The Evolution of the Novel’ since I do not believe that the novel evolved, and have spent some work demonstrating that this is one among a number of misplacements of the evolutionary metaphor – misplacements that have caused confusion (and worse) in other areas of experience (musicology and race-relations are two). But the invitation has allowed me to discriminate between, on the one hand, the effects of this misapplied metaphor on the history of past fiction and, on the other, the creative urgency with which writers have responded to evolutionary ideas in all their contradictory implications – indeed, for their contradictory implications. What has most drawn novelists, I argue, are the tensions within and between Darwinian ideas, as well as the pressures in the relation of such ideas to the human.

Fiction thrives always at points of contradiction, and evolutionary theory offered contradictory stories and contrasting trajectories for interpretation. Was this an account of development or decay? Did development inevitably imply progress, or was this a new version of the Fall? Did evolution make room for disinterestedness or did it necessitate always a ghastly struggle for too few resources? Was it communitarian or individualistic? What made evolutionary theory so fruitful for fiction was not only its coherence but its contradictions. True, it proposed a universalizing theory that would explain the history of all kinds on the earth: descent with modification, predominantly by means of the newly described and named principle, natural selection.

Cosmologists study evolution on the grandest scale of all. They aim to set our earth and our solar system in an evolutionary scheme stretching right back to the formation of the Milky Way galaxy – right back even to a so-called ‘Big Bang’ that set our entire observable universe expanding and imprinted the physical laws that govern it.

Evolution within our galaxy

Let us start with something fairly well understood – the life cycle of our sun, a typical star. About 4.5 billion years ago it condensed from an interstellar cloud, and contracted until the centre became hot enough to ignite fusion of hydrogen into helium. This process will keep it shining until, after another five billion years, the hydrogen runs out. The sun will then flare up, becoming large enough to engulf the inner planets, and to vaporize all life on earth. After this ‘red giant’ phase the inner regions contract into a white dwarf – a dense star no larger than the earth, though nearly a million times more massive.

We are quite confident about these calculations because the relevant physics has been well studied in the laboratory – atomic and nuclear physics, Newtonian gravity and so forth. Astrophysicists can just as easily compute the life cycles of stars with half the sun's mass, or twice, four times, etc. Heavier stars burn brighter, and trace out their life cycle more quickly.

Stars live so long compared to astronomers that we are granted just a single ‘snapshot’ of each star's life. But we can test our theories, by looking at the whole population of stars.

The concept of evolution means different things to different people. To a biologist it simply means genetic evolution, whereas in many other disciplines it can mean change, or unfolding, with time – sometimes with an implicit gradualness to distinguish it from revolution.

This collection of essays is the result of asking eight well-known communicators from separate disciplines to discuss evolution. It will be seen that most of them tell us how the topic has arrived where it has: the Darwinian concept of evolution itself from Stephen Jay Gould; cells and the embryo from Lewis Wolpert; the current human political divide (with a very broad brush) from Jared Diamond; society from Tim Ingold; the universe from Martin Rees; the scientific enterprise from Freeman Dyson; Richard Rogers on the evolution of cities concentrates on the current state of London and Gillian Beer considers whether novels have evolved at all and then tells us how the concept of evolution has permeated through fiction.

The essays were originally given as the Tenth Darwin College Lecture Series in early 1995. These Series have become an institution for some in Cambridge and are open to, and well attended by, the public as well as members of the College and University. The Lectures are intended to be interdisciplinary and to that end we select for each Series a group of well-known communicators, mostly from the academic world, and ask them to talk on a chosen theme. We have now had Origins, the Fragile Environment, Predictions, Communicating, Intelligence, Catastrophes, Colour and now Evolution. A greater appreciation of the overall result can best be obtained by looking at more than one volume.

The evolution of the cell is nature's greatest evolutionary triumph. That may sound rather presumptious when one compares the apparently humble cell with the complexity of organisms such as human beings, with their extraordinary brains. But in evolutionary terms, it was only once the cell had evolved that multicellular organisms became possible. Moreover, I suggest that given the eukaryotic cell – which has a nucleus, contains organelles such as mitochondria, is capable of movement and is itself evolved from the simpler bacteria – the evolution of complex structures, even the brain, was by comparison relatively simple.

Evolution as the modification of development

Development is central to the evolution of multicellular organisms: evolution proceeds by the modification of the embryo's developmental programme to produce differences in the adult. This modification is due to changes in the genes controlling development; they act by controlling cellular behaviour during development. It is by this process that, to use the French molecular geneticist Francois Jacob's phrase, evolution can tinker with embryos, using its bits and pieces to make new structures. This can be seen very clearly when one looks at the early embryos of vertebrates: they all look remarkably similar at one stage (known as the phylotypic stage) and then diverge (Figure 1). Evolution has tinkered with the basic body plan.

A clear example is the limb. While the basic form of the limb has been retained in many land vertebrates, its development has been ‘tinkered with’ to provide the bird's and bat's wings, the horse's leg and our own manipulative hand.

Adaptive continuity

Perhaps there will not always be an England (particularly on time scales favoured by palaeontologists), but a few miles of Channel and nearly a thousand years of freedom from full-scale invasion (1066 and all that) have produced a plethora of British distinctions, both idiosyncratic and deeply philosophical, from continental preferences and modes of thought. (A common language across 3000 miles of ocean can inspire more closeness than twenty miles of La Manche accompanied by a divergence of tongues – hence the similarities between American and British histories of evolutionary thought, as discussed in this article.) In this work, I try to identify adaptation as the most distinctly anglophonic subject of natural history and subsequent evolutionary ideas. I set out to show that Charles Darwin's (Figure 1) decision to site his defence and mechanism of evolution in the explanation of adaptation has roots in a long tradition of English natural history and theology that never provoked much continental attention. Our current struggles over ‘ultra-Darwinian’ versus structuralist modes of thought continue the same debate and establish a particularly English continuity across several centuries.

In the operative paragraph of his Introduction to The Origin of Species, Charles Darwin stated (1859, p. 3) that the classical subjects of natural history could provide sufficient evidence for the factuality of evolution:

Evolution

Many years ago I heard a lecture on evolution by a distinguished geneticist. Holding a stone in his hand, he observed that, were he to let it go, there was a fair degree of certainty that it would fall to the ground. With that, I am sure everyone in his audience agreed. It is equally certain, he then went on to declare, that species have evolved. This beguiling analogy has stuck in my mind ever since, for three reasons. First, declarations of certainty seem an odd place from which to start doing science. After all, it was only because Darwin refused to accept the certainty that species had been created to divine order that we have a theory of evolution at all. Secondly, I was put in mind of the objection lodged by Canon Kingsley, over a century ago, to the claim that there was a similar inevitability about the evolution of society. A dropped stone, Kingsley noted, would not necessarily hit the ground if someone decided to catch it. His point, of course, was that human freedom could not readily be comprehended within a framework of mechanical law. Thirdly, I was moved to reflect that had it not been for a colossal misunderstanding in the history of their subject, brought about through an uncritical extension of widely held ideas about social evolution to the organic domain, contemporary biologists would now be telling us that to believe that species have evolved is profoundly misguided.