My favorite book is a brilliant, revolutionary, and even dangerous work. The book is “On the Origin of Species by Means of Natural Selection” by Charles Darwin. I cherish this book for many reasons: Because I am an outspoken defender of Darwin’s ideas, because of the careful reasoning and observation Darwin showed in the book, because of the joy in learning about how living things came to be, because of the fascinating and airtight case Darwin had for evolution (even in spite of his ignorance of genetics and the meager fossil record of the time), and because this book has so much relevance today, even though it was written a century and a half ago.
The ideas presented in Origin of Species are many, yet there are three which I believe stand out most and which constitute Darwin’s key insights:
1) The Common Ancestry of Life: The millions of living things alive today are descended from “a few forms or one”.
2) Natural Selection: This is the primary mechanism which caused living things to evolve from their ancestral states.
3) Splitting: The single illustration in Origin of Species [see below] shows how Darwin believed that lineages “split” into two or more new lineages again and again over the course of evolution. The dividing of lineages must have occurred if one or a few original species evolved into the millions of species we see today. Darwin suggested that geographical separation for many generations might contribute to organisms splitting into different lineages which would then, after much time had passed, be unable to interbreed.
Darwin began his illustration of natural selection with a familiar analogy: Artificial selection, or selective breeding. Breeders select the best variety of their stock for breeding because they hope that the next generations will inherit the good characteristics of those individuals. The breeders can then alter their stock over the course of generations. Darwin said, “Breeders frequently speak of an animal’s organization as something plastic, which they can model almost as they please.”
Darwin gives several examples of natural selection: Gooseberries, for example, have been getting bigger over generations. This is fairly trivial, yet Darwin’s great insight was that selective breeding can happen without a breeder. Nature does her own breeding. Here’s how it happens: All living things tend to leave behind lots and lots of offspring. Darwin found that 100 heads of red clover produced 2,700 seeds! Obviously, all of these offspring don’t survive. There are too few resources and too little room on planet Earth for this radical increase in population to continue indefinitely. Most offspring don’t make it. There is competition between members of the same species, and losses from predators and the environment. Since many variations occur in plants and animals, it is probable that variations occur which are useful to the organism. The variation gives the organism a higher chance of survival.
Since it is a well-established fact that children tend to inherit the characteristics of their parents, we infer that organisms with beneficial variations will pass them on to their children. Their children will also have an increased chance of survival, and therefore an increased chance of getting to reproduce. So, varieties of plants and animals which have beneficial variations will, on average, leave behind more offspring than organisms without them. This occurs generation after generation until the entire species consists of only organisms with that favorable variation. This is how plants and animals evolve and become better adapted to their environments.
Darwin conjectured that all life had evolved from “one or a few” original forms. There are four main evidences supporting this: Homology, Geographical Distribution, Embryology, and Rudimentary (or Vestigial) Structures.
Darwin said, “[W]e can hardly believe that the similar bones in the arm of a monkey, in the fore-leg of the horse, in the wing of the bat, and in the flipper of the seal, are of special use to these animals. We may safely attribute these structures to inheritance.”
In other words, take a look at the similarities in the structure and arrangement of the flipper of a seal, the leg of a horse, the wing of a bat, and the arm of a monkey. Darwin explained these as being inherited from the common ancestor of these animals, with slight modifications for each animal.
Darwin noticed that animals living in the caves of America and Europe did not resemble each other as much as they resembled animals that lived in the surrounding country.
If a Creator had made the animals in the European and American caves, wouldn’t he have made the cave creatures all the same, since they lived in the same basic habitat? Why aren’t they the same? It doesn’t make sense, unless you know Darwin’s theory: American cave animals look more like American animals because the American cave animals are descended from non-cave dwelling American animals. European cave animals look like European non-cave animals because European cave animals are descended from European animals living in the surrounding country.
This explanation also works for the flora and fauna of oceanic islands. These islands, even though being similar to one another in climate, always have flora and fauna more similar to the nearest continent than to other oceanic islands. Evolution explains it perfectly: the reason is because species on oceanic islands are descended from species on the mainland. Moreover, Darwin explained that the reason Oceanic islands are almost always devoid of amphibian life is because salt water kills amphibian eggs and spawn. The only animals on these islands are those which could have made their way there naturally. Perhaps these facts seem trivial, but they’re important in the creation/evolution debate: if one admits that oceanic island species are descended from species on the mainland, then one must admit that evolution of new species has occurred, because species on the islands aren’t always the exact same species that live on the mainland.
Darwin says, “It deserves notice that it is of no importance to a very young animal, as long as it remains in its mother’s womb or in the egg, or as long as it is nourished and protected by its parent, whether most of its characters are acquired a little earlier of later in life.”
I couldn’t have said it better myself. Darwin notices that the early larval stages in crustaceans and the early embryo stages in vertebrates show a lot of similarity. This similarity may be explained by common ancestry: These embryos don’t acquire their specially-evolved characteristics until later in development because they don’t need to. It is of no importance to survival. So embryos might start out developing the way their ancestors developed and not develop any newly-evolved features until it becomes necessary for survival. If vertebrates share a common ancestor, this would explain the deep similarities seen in vertebrate development. It would explain why whale embryos develop teeth and hair, why some snakes begin to develop legs and then reabsorb them later on in development, why human beings develop a hairy coat called the lanugo which is later shed, and so on.
Darwin noticed that some flightless beetles still had wings. Darwin explained this as a holdover from the beetle’s ancestry: the flightless beetle evolved from flying beetles, and the wing, which was no longer used, gradually became smaller until it was no longer prominent, or was less prone to cause injury. Rudimentary structures are found in abundance in nature: the wings of flightless birds, the eyestalks of blind cave crustaceans that no longer have eyes, the pelvis and hind leg bones of the boa constrictor, the rudimentary tailbone and hair of a human. Those rudimentary structures are easily understood as leftovers of an evolutionary past.
Difficulties with Darwin’s theory
One remarkable thing is that Darwin answered questions about evolution which are still today parroted by creationists as if they had never been answered. Often you will hear a creationist bring up “the eye being an organ of such complexity and perfection that it could not have originated through natural selection”. Darwin soundly refuted that contention: he showed there were many intermediate eyes in the animal kingdom of varying complexity and ability to detect light. The lancelet, for example, simply has a “little sack of transparent skin, furnished with a nerve and lined with pigment, but destitute of any other apparatus.” From simple to complex, there are many eyes in the animal kingdom, each of which is useful to its possessor. It would merely take natural selection and random variation to evolve a better and better eye.
Take the old creationist chestnut, “If people came from monkeys, why are there still monkeys?” Darwin answers this, though in an abstract form. He poses the same question with different wording, “Why have not the more highly developed forms everywhere supplanted and exterminated the lower?”
He answers, “On our theory the continued existence of lowly organisms offers no difficulty; for natural selection, or survival of the fittest, does not necessarily include progressive development – it only takes advantage of such variations as arise and are beneficial to each creature under its complex relations of life.”
Chimps and humans are different because their ancestors lived in different environments and were subject to different selective pressures. For example, human ancestors lived on the savanna, where there were few trees, and where it was more efficient to walk upright. The chimp ancestors lived in the forest, in the trees, where the human’s physical advantages were not needed.
The same can be said of all other creatures: Unicellular organisms have stayed unicellular because they were never under a selective pressure where it was advantageous to become multicellular.
Darwin also addresses challenges to the fossil record. He poses the question, “The number of intermediate varieties, which have formerly existed [between fossil and living species], must be truly enormous. Why then is not every geological formation… full of such intermediate links?”
Darwin calls this, “The most obvious and serious objection” to his theory. Yet he understood that the fossil record was poor: Many fossil species, he says, are known only by a single specimen, which is often not even a complete fossil. Fossilization is rare, and with soft-bodied animals it is especially uncommon. Furthermore, there are many processes that destroy geological formations, and with them, the fossils that those formations contain. Bearing these things in mind, one would not expect a perfect fossil record.
Since Darwin’s time, this objection to his theory has been answered in a more powerful way, with advanced tools and techniques not available 150 years ago. True, the fossil record is not perfect, but there are many, many sequences of fossils which beautifully illustrate evolutionary transitions.
Origin of Species is a fascinating book in so many ways: it is beautiful to see someone carefully and critically making observations and deducing the truth. It is astonishing to see the solid case that Darwin had for evolution in spite of his ignorance of genetics and the meager fossil evidence available in his day. It’s ironic that some continue to make the same arguments against evolution without knowing that Darwin refuted them 150 years ago. It’s inspiring to know that we are the only species to discover the truth about our ultimate origins, and devastating to realize that most continue to reject it, despite the evidence. I’ll end this review with the final words from Origin of Species, which I consider to be the most profound and poetic words ever published in any book on natural history:
“From the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”