Darwin’s On the Origin of Species explains the evolution of life in terms of survival of the fittest and natural selection, and provides evidence of evolution through domestication, fossils, embryology, and more. His theory was highly controversial because of its opposition to creationism, but over time, advances in genetics and molecular biology have made evolutionary theory the scientific orthodoxy.
On the Origin of Species is Darwin’s theory that all living things evolve according to the principle of survival of the fittest. The book’s publication was a landmark in scientific history because it explained the long history of life in a concise theory. However, the publication of On the Origin of Species sparked great controversy not only among scientists, but also among religious people and the humanities, as the idea that humans, like other living things, evolved gradually was at odds with the creationism and anthropocentrism prevalent in society at the time. In this respect, Darwin’s theory of evolution is considered one of the most influential theories of all time, along with Galilei’s theory of geocentrism.
It is widely believed that Darwin was inspired by the principles of evolution while sailing the Galapagos Islands on the Beagle. Darwin developed the concept of evolution based on the fact that highly unusual species are found in places that are isolated from the outside world, such as islands in the ocean. Over the next decade of collecting and studying data, Darwin became convinced of evolution by the survival of the fittest. In fact, the idea of species changing had been around before Darwin, but there was disagreement about what caused it. On the Origin of Species, the idea of survival of the fittest is that the individuals best suited to survive in a given environment spread their offspring. Natural selection is the process by which certain variants are selected from among the many variants within a species, and because the Earth has been constantly changing for over 4 billion years, organisms have been forced to adapt. On the Origin of Species is significant because it provides concrete evidence for this evolution and its causes.
There are three main types of evidence presented in this book. The first is in Chapter 1, where he discusses domestication as an example that everyone can relate to. Humans have domesticated dogs, cows, horses, and other animals, creating many different breeds. This is done by selecting livestock with desired traits and breeding them repeatedly to make them stronger. This is an example of the accumulation of variation in organisms through selection, which is known as artificial evolution. When On the Origin of Species was published, genetic material had not yet been identified, but Darwin analyzed variation as best he could with the data available to him.
Second, Chapters 9 and 10 present visible evidence: fossils. The fossilized remains of organisms that lived billions of years ago in the strata of the Earth’s crust show us that at times like the Precambrian and Paleozoic periods, life was very different than it is today. We can also see how organisms have changed over time. However, at the time On the Origin of Species was published, not enough fossils had been found to support evolution. Darwin attributed the lack of a chain of fossils to the incompleteness of geological and paleontological knowledge. He pointed out that because of the nature of fossils, there are only a few fossils found today compared to the species that existed in the past, and because the earth’s strata are subject to uplift and subsidence, there are many phenomena that cannot be explained by the state of geology at the time.
Third, Chapter 13 explains the process of evolution as revealed by embryology and vestigial organs. There are many differences in appearance between adult fish, reptiles, birds, and mammals, which are classified as vertebrates. However, according to Chapter 13 of On the Origin of Species, the appearance of embryos is nearly identical across all vertebrates, and even mammalian embryos have gills. It also notes that giraffes have the same number of neck vertebrae as other mammals, and that bat wings, human hands, horse leg bones, and dolphin flippers all have the same bone composition. These observations strongly suggest that vertebrates evolved from a common ancestor.
In the 150 years since On the Origin of Species was published, advances in genetics have allowed us to find even more evidence of evolution, and there is no disagreement in the scientific community. However, On the Origin of Species is open to some objections based on its content alone. For starters, one could ask, “Why isn’t evolution happening now?” The evidence presented in On the Origin of Species all points to evolution happening in the past. Fossils and vestigial organs, as well as variations that can be observed in domestication or isolated areas, are all phenomena that have occurred in the past. On the other hand, we don’t see examples of chimpanzees evolving into humans or lizards evolving into eagles today. If we couldn’t prove that evolution is happening now, it would mean that the pressures of natural selection that existed in the past are now gone, and Darwin’s theory of evolution would be proven wrong.
However, since evolution is still happening, the above objection is not valid. Whether we’re walking in the warm sunshine or eating charred meat at the dinner table, mutations occur in our cells, and there’s always the possibility that these mutations could lead to evolution. In other words, species are not fixed in their current form, but are constantly evolving. It’s just that it happens so slowly that it’s hard to see it from a human perspective. It’s virtually impossible for humans to experience four billion years of evolution in a single lifetime. It’s hard to find biological differences in a person born today compared to a person born yesterday or the day before, but there are clear differences in the skull and spine compared to 10,000 years ago. Evolution happens gradually, not in a single moment, it’s just harder to observe from a human perspective.
A second argument is that the probability of evolution from simple organisms like microbes to the complex structures we have today is low given the age of the Earth. Even allowing for the accumulation of mutations by survival of the fittest, as discussed in this book, it is unlikely that life could have developed to the level of complexity we see today in 4.6 billion years. This objection can be raised because, while On the Origin of Species presents a lot of evidence for evolution, it doesn’t provide a mathematical or statistical calculation of the probability of accumulating enough mutations.
In Darwin’s time, even Mendel’s “pea experiment,” the foundation of genetics, was not known, so it would have been difficult to pinpoint the probability of evolution. Therefore, based on the book’s content alone, this objection is neither wrong nor right. Strictly speaking, this objection is also not a probability calculation, but a speculation that it is unlikely, and based on our current knowledge of molecular biology, it loses strength. Sequences are genetic material that is common to all living things. Bacteria and humans may look like completely different organisms, but in the end, it’s just a matter of the sequence and length of the four bases A, G, C, and T.
Even if the adults look very different, the sequence that contains all the information about an individual is fundamentally the same, so species can change by changing as little as 1% of the sequence. In fact, evolution is accepted as orthodoxy even in the field of studying the cumulative rate of mutation.
On the Origin of Species, the idea of evolution through the survival of the fittest was not easily accepted because it disrupted the deeply held belief that humans are the center of the world. The controversy surrounding evolution is similar to the situation when the theory of geocentrism was first proposed. As observations of the heavens revealed phenomena such as the retrograde motion of the planets and the apparent motion of the inner planets that could not be explained by the heliocentric theory, the sun was a simple explanation. However, people who had believed that the sun was the center of the world since Aristotle were not easily swayed by the evidence of geocentrism. It is difficult to be objective when looking at phenomena with a preconceived notion, but it is impossible to reject a theory based on objective evidence and proper interpretation. This book presents a vast array of evidence, including domesticated plants, fossils, embryology, and trace organs, and makes it clear that the driving force is survival of the fittest. Darwin’s theory of evolution, like Galilei’s theory of geocentrism, is a concise, yet well-reasoned explanation of a wide variety of phenomena.
