Chapter IV: Natural Selection: Or the Survival of the Fittest

Darwin noticed: “What natural selection cannot do, is to modify the structure of one species, without giving it any advantages, for the good of another species: and though statements to this effect may be found in works of natural history, I cannot find one case which will bear investigation.”

In other words, says Darwin, animals and plants were not put on Earth solely for exploitation by humankind. This is not our kingdom. Again, nothing inherently anti-deity in this but in a way rather yogic — the universe unfolds as it unfolds. We can only select whatever characteristics a given species is born with — even if it pleases us, we cannot turn donkeys into singers.


In this chapter Darwin sounds passionate. He’s spent the past three chapters dissecting the domestication process, giving example after example of how humans select domestic animals, almost lulling the reader into a state of wonder at how clever we are when it comes to manipulating plants and animals. Then “Blammo!” We’re good, Darwin says, but Nature is better. Nature acts on unseen advantages, such as organs, senses, “on the whole machinery of life.” An unfortunate use of words, machinery echoes Descartes’ idea that non-human animals were machines, devoid of mind and consciousness. I’ll come back to this, but it does imply animals have no agency.

Darwin defends his use of the term Natural Selection: because metaphors are an important way to express ideas, it’s difficult not personifying nature. Yes, the “select” implies agency but “whoever objected to chemists speaking of the elective affinities of the various elements?” Darwin writes. Mercury is not an active element, to combine it with other elements takes effort. Does that mean mercury is lazy? Anti-social? Hydrogen combines with every element in the Periodic Table (except for the non-metal group). Does that make hydrogen promiscuous? If you’re a writer, yes, hydrogen hooks up with just about anybody — it’s effective to describe distinctly non-human objects or beings in human terms — readers understand ideas better that way. But the metaphors writers use influence readers’ thinking.

Darwin explains that Natural Selection refers to the “aggregate action and product of many natural laws” adding that more familiarity with his theory, means more acceptance of the terminology. But there’s a cogntiive dissonance here with what Darwin wants us to understand as Natural Selection and how he describes it. It’s a process with no thought behind it and yet is infinitely superior to what the the most “thoughtful” animal on the planet can do, plus, the words he uses to describe the selection of traits — “a good” mutation or “bad” mutation — or even to the phrase “the survival of the fittest,” implies life, whatever the life form, has value. Humans never accept machines as having the same value as life.

So let’s go back to Descartes and the idea of animals as complex organic machines. It leaves no room in Western thought for a world view that includes agency on the part of every life form in an ecosystem and recognizing that is actually key to a healthy ecological relationship when the top predator has enormous advantages (brain power.) Giving life forms agency might be a functional way to protect an ecosystem from overexploitation. Without the ability to assess and do something about, oh, say climate change, we may as well be just a supercolony of ants. (Maybe we really are.) By robbing other creatures of agency, a culture gives itself permission to take indefinitely.

Darwin & Relationships

Darwin Noticed:  “In Australia the imported hive-bee is rapidly exterminating the small, stingless native bee.”

Hats off to Darwin. Just when I think “Surely you could have cut to the chase Charles…” he sums up an idea with clarity and brevity. Maybe his affliction (he did have a loo installed in his study, something you don’t see in the postcards) provided the impetus for getting to the point.

 Struggle for Life most severe between Individuals and Varieties of the same Species is the final bit of Chapter III. A good science writer uses examples so lay readers can draw a picture in their minds — hive-bee versus the solitary native bee. Darwin cites other invasive species that do far better in a novel environment than the indigenous species: rats, cockroaches, and swallows. “…but probably in no one case could we precisely say why one species has been victorious over another in the great battle of life,” Darwin writes.

Battle, victory, struggle; why did Darwin choose these words? Did word choice set the stage for evolutionary theory being so focused on competition that what he wrote in the follow up paragraph took a longer time to absorb into the collective psyche? Each form of life has a relationship with every other form of a life in a given habitat, Darwins writes, and we can’t predict those relationships.

Take an insect like the Red Imported Fire Ant (RIFA) from Brazil and set it loose in Alabama: the climate might be similar, but it will have different relationships with the novel life forms it encounters in a new habitat. We can never anticipate what the relationships will be. The idea is a big part of environmental education today. But who was reading Darwin in the late 19th century, anyone? Definitely not the guy who released European starlings in New York City in 1890.

"It is good thus to try in imagination to give to any one species an advantage of another," Darwin writes. "Probably in no single instance should we know what to do. This ought to convince us of our ignorance on the mutual relations of all organic beings; a conviction as necessary, as it is difficult to acquire."

So the “struggle for existence” could just as easily be the less catchy — “lucky advantages”

But, for Darwin, war it is. Thankfully, though, it’s painless compared with human war. I guess. “When we reflect on this struggle, we may console ourselves with the full belief, that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply.”

A Population Checked: Competition, Climate & Predation

Darwin had the handy Parslow as butler, a cook, gardeners — servants of all kinds to keep Down House running. Still, it’s impressive how he used his own time. When you read The Origin of Species, and think of how you spend your own days, watching Downton Abbey or The Hour seems a shocking waste of time. “There must be some worms or weeds I can study!”

Following Darwin’s Malthusian-inspired musings on populations, he turns to what keeps a species in check. At different stages of life, some species are particularly vulnerable — as eggs, for example. Plants seeds, too, suffer enormously, mostly because they’re choked by the vegetation already on the ground. They have no hope with the competing growth. And this is where you think what would have happened had Darwin grown up with video games?

Ever curious, Darwin digs (or probably a gardener digs) a patch three feet by two feet to get rid of any competing vegetation and watches what happens. Each of the 357 weeds that come up, he identifies and marks, and waits to see what happens. Will they all live? Slugs and insects are the chief nemesis of 295 of the weeds.

Darwin also keeps a three feet by four feet patch of turf unmowed or not browsed by animals. Out of 20 plant species, nine species never make it.

Lest his readers start musing on the vulnerabilities of the young in obtaining food, and how food determines populations, Darwin reminds us that plants and animals are some species’ meal ticket. He’s setting the stage for the concept of a food web. Before that, he has to explain another factor: climate, which sometimes has a direct bearing on population: the bitter winter of 1884-5 destroyed four-fifths of the birds on his grounds. But hang on, says Darwin. “Climate brings on the most severe struggle between individuals, whether of the same or distinct species, which subsist on the same kind of food.”

So let’s say its a bad year for salmon because when juveniles headed to the ocean to get big and strong before migrating back to their natal streams, the climate was not in their favour. They had less food. Fewer salmon come back, which is bad for bears. Bad for humans too, but which species will ultimately get more salmon: humans or bears?

Malthus, Charles Darwin, and Planet Elephant


African Elephant, Tanzania (Muhammad Mahdi Karim)

In Chapter III, The Struggle for Existence, Darwin talks elephants. He’s explaining the whole Malthusian concept of what happens when populations grow unchecked, even slow-growing mammals like elephants. In the late 19th century, elephants were considered the slowest breeders. (Nowadays, orangutans hold that distinction.)

Darwin calculates it this way: elephants (he doesn’t specify African or Asian) start to breed at around age 30. They breed to 90 years old. In that time, one elephant has 6 offspring, plus they live to 100 (they actually live to about 65 in the wild). Darwin calculated that after 740 to 750 years, the world would be a richer place with 19 million descendants of the original pair. Darwin didn’t exactly call the world a richer place with more elephants — and that’s the problem with not reading Darwin  but trusting only Huxley’s interpretation of Darwin, or Dawkins, or whomever. It was an interesting point brought up by Frans de Waal at the American Association for the Advancement of Science plenary talk (February 20, 2012)

Read Darwin and you get the sense he is using his culture and language as an arsenal to get readers to understand the idea of natural selection. And in doing so, he opens up his writing to a reader’s interpretation, based on their own worldview. In Dawkin’s case, as de Waal says, as a combative atheist. But a church goer can read the following sentence and be assured natural selection is no threat to his religion because it is a wonder all on its own:

"We see these beautiful co-adaptations most plainly in the woodpecker and the mistletoe; and only a little less plainly in the humblest parasite which clings to hairs of a quadraped or feathers of a bird; in the structure of the beetle which dives through the water; in the plumed seed which is wafted by the gentlest breeze; in sort, we see beautiful adaptations everywhere and in every part of the organic world." (p. 76, 6th edition.)

To Darwin, the urgent need is for people to understand how natural selection works…”unless it’s thoroughly ingrained in the mind, the whole economy of nature with every fact on distribution, rarity, abundance, extinction, and variation, will be dimly seen or quite misunderstood.” (p. 77, 6th edition.)

So why elephants as an example? They’re memorable, visual examples for a lay reader. As a science writer for kids, I often use elephants to explain size, weight, or something silly. Elephants are fun. Visit the Darwin home, Down House, and you get an idea of how much Charles and Emma enjoyed their kids. Maybe Charles explained scientific concepts to them in playful, easy ways, which then made its way into his writing.

Chapter Two: Individual Differences: Darwin underscores variation within a species

In Chapter II, Variations under Nature, Darwin starts by acknowledging that it’s tough to pin down what a species is and what variety means. He defines the problem naturalists have always had: at what point is a deviation from the norm just a deviation from the norm, or a new variety? Categorization is based on observable traits — phenotype, a word only coined about 50 years after The Origin of the Species. Observable traits, Darwin notes, can vary widely within a species. He points out an observational bias of the ”systematists” (taxonomists) who are too devoted to the idea of the intransigence of an organism’s important characteristics, sometimes even ranking the importance of individual organs. The same taxonomists ascribe variation only among non-important traits. Non-important being something that has nothing to do with an organism’s ability to reproduce successfully.

Darwin got me thinking about observer bias.

To a certain extent “observable” depends on what an observer believes is important. Some characteristics are obviously important — a bat without echolocation abilities is a dead bat.

But importance is often tied up with context. Take the the two-barred flasher butterfly from Central America, for example. The Tzeltal people in southern Mexico have a number of names for the butterfly. To outsiders, there appears to be no differences to warrant multiple species names, unless you look at the butterfly’s larvae — the caterpillars. Different types of larvae eat different crops, which is important to the Tzeltal people, and they reflected that importance in their own taxonomy of the butterflies. The different names for what appears to be the same butterfly puzzled Western scientists for years because they never considered the butterflies’ relationship with crops.

You could say the same about settlers to the West Coast of Canada and their encounter with Pacific salmon. Hudson’s Bay Company men wrote about salmon all the time in the Journals of Fort Langely (men in charge of HBC trade posts kept diaries, in this case for Fort Langley, 1827 to 1830.) Yet they rarely mentioned any of the five species of Pacific salmon. European settlers would have been used to Atlantic salmon. But to the inhabitants of the West Coast, the five salmon species, the different populations within a species, and the healthy numbers of individuals within a population were (and are) extraordinarily important.

In all fairness, any settler living long enough on the coast or along the Fraser River probably quickly realized Pacific salmon were a very different breed of salmon from Atlantic. Just as likely, however, they failed to understand the implication of variety, especially among the species most sought for canning — sockeye. A sockeye is not just a sockeye, no matter how alike they look. Some sockeye are powerhouses with a physiological toolkit that propels them over a thousand kilometres upstream, in fluctuating temperatures, to spawn in their native river. Other sockeye could never make that journey — they’re adapted to short journeys within a tight temperature zone (like the Weaver Creek sockeye in the photo.) And within each population will be individual differences.

In Individual Differences, the first subhead of Chapter II, Darwin writes: “These individual differences are of the highest importance for us, for they are often inherited, as must be familiar to everyone; and they thus afford the materials for natural selection to act on and accumulate, in the same manner as man accumulates in any given direction individual differences in his domesticated productions.”

Darwin goes on to shoot down this rigid adherence to the intransigence of important traits by bringing up dimorphism and trimorphism. Species, an arbitrary concept in some ways, are not fixed and variation is the norm, and without it, well, life would not evolve.