On "On the Origin of Species"

I am indebted to Adèle van Reeth's Les chemins de la philotophie for enthusing me in reading Darwin's controversial masterpiece On the Origin of Species. We live in a time when creationism under the guise of so-called Intelligent design is again on the rise, when more and more people from developed countries, including highly-educated people, can believe Earth is flat, when post-truth is a thing, and people can attract and retain the attention of millions with any kind of bullshit. Darwin published his book in the middle of the XIXth century, at a time when creationism was still dominant, and the religious dogma considered relevant on the matter of truth of natural sciences' theories, especially ones dependent on pre-historical and geological times facts. So it seemed important to me to understand how Darwin exposed his theory, how he actually practiced science and conveyed scientific truth.

Book Structure

The book is structured in three unequal parts. The first part introduces the concept of variations in the morphology, habits, behaviours, and structure of living beings, and explains how even seasoned naturalists have a hard time defining the boundary of species or varieties precisely. It exposes the central problem Darwin is trying to solve, namely why those variations happen and how species and varieties are shaped.

The second part defines Darwin's Natural selection theory, its various constitutive principles -Survival of the fittest, random variations, sexual selection - and how this theory explains the formation and evolution of all living beings.

The third and longest part is a careful and systematic analysis of facts that potentially contradict the Natural selection principle, from the question of how instinctual behavior of neutered individuals could possibly be inherited, to the question of geographical distribution of related species, through difficulties stemming from findings in fossils and geological records. The conclusion summarises Darwin's findings, theory and arguments that support it.

Natural Selection

Darwin's theory, namely Natural selection, is thus named by analogy with how humans select domestic animals and plants for their greater benefits. Its principles can be summarised by the following "laws":

Living organisms, through reproduction, tend to proliferate and grow in numbers which, when left unopposed, leads to population explosion,

This tendency is counterbalanced by high mortality rate stemming from intense competition for resources within an ecosystem, both within species and among species, with an infinite variation of complex relationships from the simple prey/predator to symbiosis, parasitism or even relations involving several species,

This intense competition leads to survival of the fittest, whereby individuals use the slightest advantage they have "acquired" that can provide them an edge and higher survival rate,

Such variations appear constantly within species (we would call them mutations), sometimes minute, sometimes spectacular, in a random and unpredictable way,

"Survival of the fittest" principle will thus preserve variations which provide an edge in the competition, and reproduction, under normal circumstances, allow passing those variations to descendants of survivors,

Sexual selection is a secondary principle that ensures individuals carrying beneficial variations will have a higher reproduction rate, increasing the likelihood of preserving an advantage over the next generations.

Natural selection is a term that summarizes those complex interactions occurring within a specific biotope between all the living beings, leading to evolution of species towards better adaptation to the milieu and to other species, which species in return affect the milieu through their constant evolution (think for example of how plants evolve in reaction to changes in the diet of animals and the increase in herbivorous population).

The key aspect of Darwinism and the one that sparked and still sparks most controversy is the fundamentally random nature of the variations. We now know those variations mostly result from gene mutations but those mutations are still mostly random, or at least unpredictable, and Nature acts much like a farmer does by selecting the best variations, the ones providing a competitive advantage, over the others. The appearance of "intelligent design" or "masterplan" comes from our very narrow view and the difficulties we are having intellecting the unfathomable spans of time which Nature has at its disposal to act: When we contemplate the beauty of the interaction of bees and flowers, the intricacies of ants' social life, or the perfection of the jaguar, we forget they are the result of tens or hundreds of millions of years of constant minute variations and selection, accumulated over millions of generations.

Why we must read Darwin

This book is a great read for many reasons which can be condensed by saying it's the epitome of scientific writing. For the detail-inclined among us, here is what I put behind those vague words:

It's written without much jargon, or at least a jargon that has become mainstream over the past 150 years. Darwin does not make use of footnotes, or any kind of notes for that matter, even though he provides a bibliography at the end of the book albeit structured somewhat informally and without exact references, which from the point of view of the reader avoids constant back and forth between body and appendices one is forced to go through when reading modern scholarly texts,

It's filled with abundance of concrete examples illustrating various points of the theory or thorny problems it is facing, from the innumerable variations of the pigeons to the sophisticated behaviour of ants, through the problems posed by the dissemination of terrestrial species, both plants and animals across large bodies of water,

A lot of examples come from personal observations and concrete experiences run by Darwin himself over the 20 or 25 years preceding the publication of his book, as well as from the wealth of publications and personal communications from other scholars all around the world, which demonstrates Darwin was not only a brilliant mind but first and foremost an empiricist who spent his life collecting facts and observations, and a scientist embedded in a complex web of relations, discussions, controversy with his peers,

Darwin always adopts a humble stance when presenting his ideas and the facts supporting it. He never says "This is the truth and you must believe" but instead repeats "those facts appear to me to support my theory" or "No other theory (fixism) can explain all the facts consistently",

Most importantly, he spends about two-third of his book exposing, analysing every possible problem arising from facts and theories of the sciences of his time, geology, anatomy, botanics, zoology, geography, putting in practice what would be theorised seventy years later by Karl Popper as empirical falsification: What makes a theory scientific is that it can potentially be disproven by facts, through empirical research and experiments. Hence the emphasis Darwin puts on examining facts that could contradict his theory.

A common rebuttal of evolutionism is the fact we have very little evidence or sequence of variations of a species from fossils, something which has been used by creationist as a "proof" that species were actually created once and for all. But Darwin demonstrates that when it comes to geological evidences, we are like the drunkard who looks for his keys under the gaslight: We infer theories from a very narrow view of the world, not taking into account the thousands or millions of years that can separate fossiliferous layers, the very peculiar conditions that are needed for fossils to accumulate (sedimentation of material, shallow and slowly receding bodies of water, climatic conditions in arctic lands...), in other words how spotty and sketchy our evidence are. But from those few and far between pieces of evidence, we can still detect the effect of natural selection and continuous variations which supports the "simplest" explanation.

At least, next time Jehovah's Witnesses ring at my door and want to discuss why Darwinism is wrong, and how God created the Earth and all the living beings populating it around 6000 BC, I will feel armed and prepared to counter every argument, given they are basically unchanged since Darwin's time, more than 150 years ago.

NOTE: Being a developer, I have tried to encode Darwin's theory into a simple command-line application showing the evolution of species on a "planet" with varying biotopes.

NOTE 2: Many thanks to Anna Savarin for the proofreading!