The Diversity of Life by E.O. Wilson (1992)

It is a failing of our species that we ignore and even despise the creatures whose lives sustain our own. (p.294)

Edward Osborne Wilson was born in 1929 and pursued a long career in biology, specialising in myrmecology, the study of ants, about which he came to be considered the world’s leading expert, and about which he published a massive textbook as well as countless research papers.

As well as his specialist scientific writing, Wilson has also published a series of (sometimes controversial) books about human nature, on collaborative species of animal (which led him to conceive the controversial theory of sociobiology), and about ecology and the environment.

(They’re controversial because he considers humans as just another complex life form, whose behaviour is dictated almost entirely by genetics and environment, discounting our ability to learn or change: beliefs which are opposed by liberals and progressives who believe humans can be transformed by education and culture.)

The Diversity of Life was an attempt to give an encyclopedic overview of life on earth – the myriads of life forms which create the dazzlingly complicated webs of life at all levels and in all parts of our planet – and then to inform the reader about the doleful devastation mankind is wreaking everywhere – and ends with some positive suggestions about how to try & save the environment, and the staggering diversity of life forms, before it’s too late.

The book is almost 30 years old but still so packed with information that maybe giving a synopsis of each chapter would be useful.

Part one – Violent nature, resilient life

1. Storm over the Amazon An impressionistic memoir of Wilson camping in the rainforest amid a tropical storm, which leads to musings about the phenomenal diversity of life forms in such places, and beyond, in all parts of the earth, from the Antarctic Ocean to deep sea, thermal vents.

2. Krakatau A vivid description of the eruption of Krakatoa leads into an account of how the sterile smoking stump of island left after the explosion was swiftly repopulated with all kinds of life forms within weeks of the catastrophe and now, 130 years later, is a completely repopulated tropical rainforest. Life survives and endures.

3. The Great Extinctions If the biggest volcanic explosion in recorded history can’t eliminate life, what can? Wilson explains the five big extinction events which the fossil record tells us about, when vast numbers of species were exterminated:

  • Ordovician 440 million years ago
  • Devonian 365 million years ago
  • Permian 245 million years ago
  • Triassic 210 million years ago
  • Cretaceous 66 million years ago

The last of these being the one which – supposedly – wiped out the dinosaurs, although Wilson points out that current knowledge suggests that dinosaur numbers were actually dropping off for millions of years before the actual ‘event’, whatever that was (most scientists think a massive meteor hit earth, a theory originally proposed by Luis Alvarez in 1980).

Anyway, the key thing is that the fossil record suggests that it took between five and 20 million years after each of these catastrophic events for the diversity of life to return to something like its pre-disaster levels.

Part two – Biodiversity rising

4. The Fundamental Unit A journey into evolutionary theory which quickly shows that many of its core concepts are deeply problematic and debated. Wilson clings to the notion of the species as the fundamental unit, because it makes sense of all biology –

A species is a population whose members are able to interbreed freely under natural conditions (p.36)

but concedes that other biologists give precedence to other concepts or levels of evolution, for example the population, the deme, or focus on genetics.

Which one you pick depends on your focus and priorities. The ‘species’ is a tricky concept to define, with the result that many biologists reach for subspecies (pp.58-61).

And that’s before you examine the record chronologically i.e. consider lineages of animals which we know stretch back for millions of years: at what point did one species slip into another? It depends. It depends what aspects you choose to focus on – DNA, or mating rituals, or wing length or diet or location.

The message is that the concepts of biology are precise and well-defined, but the real world is far more messy and complicated than, maybe, any human concepts can really fully capture.

5. New Species Wilson details all the processes by which new species have come about, introducing the concept of ‘intrinsic isolating mechanisms’, but going on to explain that these are endless. Almost any element in an environment, an organisms’s design or DNA might be an ‘isolating mechanism’, in the right circumstances. In other words, life forms are proliferating, mutating and changing constantly, all around us.

The possibility for error has no limit, and so intrinsic isolating mechanisms are endless in their variety. (p.51)

6. The forces of evolution Introduces us to a range of processes, operating at levels from genetics to entire populations, which drive evolutionary change, including:

  • genetic mutation
  • haploidy and diploidy (with an explanation of the cause of sickle-cell anaemia)
  • dominant and recessive genes
  • genotype (an individual’s collection of genes) and phenotype (the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment)
  • allometry (rates of growth of different parts of an organism)
  • microevolution (at the genetic level) and macroevolution (at the level of environment and population)
  • the theory of punctuated equilibrium proposed by Niles Eldredge and Stephen Jay Gould (that evolution happens in burst followed by long periods of no-change)
  • species selection

7. Adaptive radiation An explanation of the concepts of adaptive radiation and evolutionary convergence, taking in Hawaiian honeycreepers, Darwin’s finches on the Galapagos Islands, the cichlid fish of Lake Victoria, the astonishing diversity of shark species, and the Great American Interchange which followed when the rise of the Panama Isthmus joined previously separated North and South America 2.5 million years ago.

Ecological release = population increase that occurs when a species is freed from limiting factors in its environment.

Ecological constraint = constriction in the presence of a competitor.

8. The unexplored biosphere Describes our astonishing ignorance of how many species there are in the world. Wilson gives the total number of named species as 1.4 million, 751,000 of them insects, but the chapter goes on to explain our complete ignorance of the life forms in the ocean depths, or in the rainforest canopies, and the vast black hole of our ignorance of bacteria.

There could be anything between 10 million and 100 million species on earth – nobody knows.

He explains the hierarchy of toxonomy of living things: kingdom, phylum or division, class, order, family, genus, species.

Equitability = the distribution of diversity in a given location.

9. The creation of ecosystems Keystone species hold a system together e.g. sea otters on the California coast (which ate sea urchins thus preventing the sea urchins eating the kelp, so giving rise to forests of kelp which supported numerous life forms including whales who gave birth close to the forests of kelp) or elephants in the savannah (who, by pushing over trees, create diverse habitats).


The predator paradox – in many systems it’s been shown that removing the top predator decreases diversity).

Character displacement. Symbiosis. The opposite of extinction is species packing.

The latitudinal diversity gradient i.e. there is more diversity in tropical rainforests – 30% of bird species, probably over half of all species, live in the rainforests – various theories why this should be (heat from the sun = energy + prolonged rain).

10. Biodiversity reaches the peak The reasons why biodiversity has steadily increased since the Cambrian explosion 550 million years ago, including the four main steps in life on earth:

  1. the origin of life from prebiotic organic molecules 3.9 billion years ago
  2. eukaryotic organisms 1.8 billion years ago
  3. the Cambrian explosion 540 to 500 million years ago
  4. the evolution of the human mind from 1 million to 100,000 years ago.

Why there is more diversity, the smaller the creatures/scale – because, at their scale, there are so many more niches to make a living in.

Part three – The human impact

It’s simple. We are destroying the world’s ecosystems, exterminating untold numbers of species before we can even identify them and any practical benefits they may have.

11. The life and death of species ‘Almost all the species that have ever lived are extinct, and yet more are alive today than at any time in the past (p.204)

How long do species survive? From 1 to 10 million years, depending on size and type. Then again, it’s likely that orchids which make up 8% of all known flowering plants, might speciate, thrive and die out far faster in the innumerable microsites which suit them in mountainous tropics.

The area effect = the rise of biodiversity according to island size (ten times the size, double the number of species). Large body size means smaller population and greater risk of extinction. The metapopulation concept of species existence.

12. Biodiversity threatened Extinctions by their very nature are rarely observed. Wilson devotes some pages to the thesis that wherever prehistoric man spread – in North America 8,000 years ago, in Australia 30,000 years ago, in the Pacific islands between 2,000 and 500 years ago – they exterminated all the large animals.

Obviously, since then Western settlers and colonists have been finishing off the job, and he gives depressing figures about numbers of bird, frog, tree and other species which have been exterminated in the past few hundred years by Western man, by colonists.

And now we are in a new era when exponentially growing populations of Third World countries are ravaging their own landscapes. He gives a list of 18 ‘hotspots’ (New Caledonia, Borneo, Ecuador) where half or more of the original rainforests has been heart-breakingly destroyed.

13. Unmined riches The idea that mankind should place a cash value on rainforests and other areas of diversity (coral reefs) in order to pay locals not to destroy them. Wilson gives the standard list of useful medicines and drugs we have discovered in remote and unexpected plants, wondering how many other useful, maybe life-saving substances are being trashed and destroyed before we ever have the chance to discover them.

But why  should this be? He explains that the millions of existing species have evolved through uncountable trillions of chemical interactions at all levels, in uncountably vast types of locations and settings – and so have been in effect a vast biochemical laboratory of life, infinitely huger, more complex, and going on for billions of years longer than our own feeble human laboratory efforts.

He gives practical examples of natural diversity and human narrowness:

  • the crops we grow are a handful – 20 or so – of the tens of thousands known, many of which are more productive, but just culturally alien
  • same with animals – we still farm the ten of so animals which Bronze Age man domesticated 10,000 years ago when there is a world of more productive animals e.g. the giant Amazon river turtle, the green iguana, which both produce far more meat per hectare and cost than beef cattle
  • why do we still fish wild in the seas, devastating entire ecosystems, when we could produce more fish more efficiently in controlled farms?
  • the absolutely vital importance of maintaining wild stocks and varieties of species we grow for food:
    • when in the 1970s the grassy-stunt virus devastated rice crops it was only the lucky chance that a remote Indian rice species contained genes which granted immunity to the virus and so could be cross-bred with commercial varieties which saved the world’s rice
    • it was only because wild varieties of coffee still grew in Ethiopia that genes could be isolated from them and cross-bred into commercial coffee crops in Latin America which saved them from devastation by ‘coffee rust’
  • wipe out the rainforests and other hotspots of diversity, and there go your fallback species

14. Resolution As ‘the human juggernaut’ staggers on, destroying all in its path, what is to be done? Wilson suggests a list:

  1. Survey the world’s flora and fauna – an epic task, particularly as there are maybe only 1,500 scientists in the whole world qualified to do it
  2. Create biological wealth – via ‘chemical prospecting’ i.e. looking for chemicals produced by organisms which might have practical applications (he gives a list of such discoveries)
  3. Promote sustainable development – for example strip logging to replace slash and burn, with numerous examples
  4. Wilson critiques the arguments for
    • cryogenically freezing species
    • seed banks
    • zoos
  5. They can only save a tiny fraction of species, and then only a handful of samples – but the key factor is that all organisms can only exist in fantastically complicated ecosystems, which no freezing or zoosor seed banks can preserve. There is no alternative to complete preservation of existing wilderness

15. The environmental ethic A final summing up. We are living through the sixth great extinction. Between a tenth and a quarter of all the world’s species will be wiped out in the next 50 years.

Having dispensed with the ad hoc and limited attempts at salvage outlined above, Wilson concludes that the only viable way to maintain even a fraction of the world’s biodiversity is to identify the world’s biodiversity ‘hot spots’ and preserve the entire ecosystems.

Each ecosystem has intrinsic value (p.148)

In the last few pages he makes the ‘deepest’ plea for conservation based on what he calls biophilia – this is that there is all kinds of evidence that humans need nature: we were produced over 2 million years of evolution and are descended from animals which themselves have encoded in the genes for their brains and nervous systems all kinds of interactions with the environment, with sun and moon, and rain and heat, and water and food, with rustling grasses and sheltering trees.

The most basic reason for making heroic efforts to preserve biodiversity is that at a really fundamental level, we need it to carry on feeling human.

On planet, one experiment (p.170)


Obviously, I know human beings are destroying the planet and exterminating other species at an unprecedented rate. Everyone who can read a newspaper or watch TV should know that by now, so the message of his book was over-familiar and sad.

But it was lovely to read again several passages whose imaginative brio had haunted me ever since I first read this book back in 1994:

  • the opening rich and impressionistic description of the rainforest
  • a gripping couple of pages at the start of chapter five where he describes what it would be like to set off at walking pace from the centre of the earth outwards, across the burning core, then into the cooler mantle and so on, suddenly emerging through topsoil into the air and walking through the extraordinary concentration of billions of life forms in a few minutes – we are that thin a layer on the surface of this spinning, hurtling planet
  • the couple of pages about sharks, whose weird diversity still astonishes
  • the brisk, no-nonsense account of how ‘native’ peoples or First Peoples were no tender-hearted environmentalists but hunted to death all the large megafauna wherever they spread
  • the dazzling description of all the organisms which are found in just one pinch of topsoil

As to the message, that we must try and preserve the diversity of life and respect the delicate ecosystems on which our existence ultimately depends – well, that seems to have been soundly ignored more or less everywhere, over the past thirty years since the book was published.


The Diversity of Life by Edward O. Wilson was published by the Harvard University Press in 1992. All references are to the 1994 Penguin paperback edition.

Related links

Reviews of other science books





Human evolution


Origins of Life

Particle physics


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1 Comment

  1. Hi Simon,

    Thank you for reviewing this 1992 seminal book “The Diversity of Life” by Edward O Wilson, who has given us the terms “biodiversity” and “biophilia”. I appreciate your good effort.

    I have owned a copy of the book for 20 odd years. Would you agree and/or recommend that we could learn a great deal about ourselves and Nature via the notion of “Biophilia” as first proposed by Edward O Wilson?

    I too have a book to recommend you. It is Edward O Wilson’s “Consilience: The Unity of Knowledge”, which is a national bestseller. Wilson has received many fellowships, awards and honours, including two Pulitzer prizes.


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