Book Review – On the Origin of Species (How did evolution create so many different species?)

Charles Darwin’s book “On the Origin of Species” explains Darwin’s theory that all living things have evolved by the principle of survival of the fittest, using a variety of evidence.

 

On the Origin of Species is Darwin’s argument that all living things evolved by the principle of survival of the fittest. The book’s publication was a milestone in scientific history because it explained the long history of life with a simple theory. However, the publication of On the Origin of Species sparked a great deal of controversy not only among scientists, but also among religious people and the humanities, as the idea that humans, like other living things, evolved gradually went against the creationism and anthropocentrism prevalent in society at the time. In this sense, Darwin’s theory of evolution is considered to be one of the most influential theories of all time, along with Galilei’s theory of geocentrism.
Darwin famously sailed the Beagle to the Galapagos Islands, where he was inspired by the principles of evolution. He was inspired by the fact that very unusual species are found in places that are isolated from the outside world, such as islands in the ocean. Darwin spent the next decade collecting and studying the data and became convinced of evolution by the survival of the fittest. In fact, the idea of species changing had been around since before Darwin, but there was disagreement about what caused it. According to On the Origin of Species, the fittest individuals are the ones best suited to survive in a given environment and spread their offspring. This process of selecting from the many variations within a species is known as natural selection. Since the Earth has been constantly changing for over 4 billion years, organisms have been forced to constantly adapt. On the Origin of Species is significant because it provides a concrete rationale for this evolution and its causes.
There are three main ways in which the book presents this evidence. First, Chapter 1 presents evidence that everyone can relate to: domestication. Humans have domesticated dogs, cows, horses, and other animals, creating many different breeds. This process of selecting and breeding livestock with desirable traits takes advantage of the phenomenon that traits become stronger over time. This is an example of the accumulation of variation in organisms through selection, and is known as artificial evolution. When On the Origin of Species was published, genetic material had not yet been identified, but here Darwin analyzes variation as best he could based on the data available at the time.
Then, in chapters 9 and 10, he presents the visible evidence: fossils. The fossilized remains of organisms that lived billions of years ago in layers of strata show us that in periods like the Precambrian and Paleozoic, life was very different than it is today. We can also see how creatures have changed over time. However, at the time On the Origin of Species was published, there were not enough fossils to support evolution. Darwin attributes the lack of fossils in the form of a chain of evolutionary processes to the incompleteness of geological and paleontological knowledge. He points out that because of the nature of fossils, we have only found a small fraction of 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 understood at the level of geology at the time.
Finally, Chapter 13 describes 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 embryo is nearly identical in all vertebrates, and even mammalian embryos have gills. It also points out 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.
Now, 150 years after On the Origin of Species was published, advances in genetics have allowed us to find much more evidence of evolution, and there is no disagreement in the scientific community. However, if we only think about the content of On the Origin of Species, there are objections. First of all, we can ask why evolution isn’t happening now. This is because the evidence presented in On the Origin of Species only shows evolution in the past. Fossils and vestigial organs, as well as the variation we observe in domestication and isolated areas, all happened in the past. Today, we don’t see chimpanzees evolving into humans, or lizards evolving into eagles. If we couldn’t prove that evolution is happening now, then Darwin’s theory of evolution would be proven wrong because it would mean that the pressures of natural selection that existed in the past are no longer present.
However, evolution is still happening, so the above rebuttal is not valid. Whether we’re walking down the street in the warm sunshine or eating charred meat at the dinner table, mutations are occurring in our cells, and there’s always the possibility that they could lead to evolution. In other words, species are not defined by what they are today, but are constantly evolving. It’s just that it’s happening at a very slow pace. It’s virtually impossible to experience evolution over four billion years in our lifetimes. It’s hard to see any biological differences between people born today and those born yesterday or the day before, but if you add up each day and go back 10,000 years, there are clear differences in skulls and spines. Evolution is difficult to observe from a human perspective because it happens gradually, not in a single moment.
A second argument is that the probability of evolution from simple forms of life, such as microorganisms, to the complex structures we see today is low given the age of the Earth. The book acknowledges the accumulation of mutations by the survival of the fittest, but argues that 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 provides plenty of evidence for evolution, it doesn’t provide a mathematical or statistical representation of the probability of accumulating enough mutations.
In Darwin’s day, even Mendel’s “pea experiment,” the foundation of genetics, was not yet known, so he would not have been able to estimate the probability of evolution. So, based on the book’s content alone, this objection is neither wrong nor right. Strictly speaking, this rebuttal is not a probability calculation, but rather a speculation that it is unlikely. And based on our current knowledge of molecular biology, this objection to probability is even weaker. Sequences are genetic material that is common to all living things. Bacteria and humans may seem like completely different organisms, but at the end of the day, they only differ in the order in which the four bases A, G, C, and T are arranged and how long they are.
Even though the adult organisms may look very different, the sequence that contains all the information about the individual is fundamentally the same, so it only takes a 1% change in the sequence to change into a different species. In fact, evolution is the accepted wisdom, even in the field of studying the cumulative rate of mutations.
The reason why evolution through survival of the fittest, the thesis of On the Origin of Species, is so difficult for people to accept is that it deviates from the 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 motions of the planets and the apparent motions of the inner planets that were difficult to explain using the traditional heliocentric theory, the sun was a simple explanation. However, people who had firmly believed that the sun was the center of the world since Aristotle were not easily convinced by the evidence of geocentrism. In this way, if you look at a phenomenon with a conclusion already in your mind, you cannot make an objective judgment. However, we cannot deny theories that are based on objective evidence and proper interpretation. This book presents a vast array of data from domestication, fossils, embryology, and trace organs, and makes it clear that the driving force is survival of the fittest. Darwin’s theory of evolution is as simple as Galilei’s theory of geocentrism, yet it explains a wide variety of phenomena.