The theory of evolution explains how organisms adapt and change over generations to their environment through genetic variation and natural selection. From ancient times to Darwin, there have been many different theories of evolution, and today, neo-Darwinism, a combination of Darwin’s theory of natural selection and Mendelian genetics, is the accepted theory. The theory serves as an important scientific foundation for understanding the origin of species and biodiversity, and it continues to evolve.
Evolutionary theory, in its broadest sense, refers to the entire theory of evolution, which is simply the process by which heritable traits change among populations of organisms. When we think of evolutionary theory, we usually think of Darwin’s theory of evolution and its subsequent developments, but the idea of evolution has been around since the time of the ancient Greeks. For example, philosophers such as Empedocles (ca. 490-430 BC) and Anaximander (ca. 610-546 BC) were among the first to think about evolution. So the idea of evolution was around long before Darwin.
After the ancient Greek philosophers, the scientific approach to species and their origins didn’t really take off until the 17th century. The modern theory of evolution is the work of Lamarck (1744-1829), who argued that all living things develop over generations into increasingly more complete and complex forms. According to Lamarck’s theory, the simpler the organism that exists today, the shorter its origin. Lamarck also argued that acquired traits, such as muscles developed through life, are passed on to offspring, but he failed to provide evidence for this and was subsequently criticized. Lamarck’s theory and other theories were criticized and criticized, leading to Darwin’s (1809-1882) theory of evolution, which is widely accepted today.
Darwin codified his theory of evolution in his book On the Origin of Species (1859). His theory is the basis and foundation of modern evolutionary theory, and to summarize the main points of The Origin of Species, it boils down to four key conditions.
First, all species have the ability to reproduce through self-replication. For example, a lion and a tiger that are genetically close may have offspring, but these offspring are not fertile and therefore do not qualify as a new species. Therefore, self-replication is an essential prerequisite for the evolutionary process.
Second, variation occurs during the replication process. Variations, such as mutations, create differences between individuals, and these differences are often inherited. If self-replication were perfect, evolution would not occur. It is the imperfection of the self-replication process, the instability of mutability, that makes evolution possible. Traits such as acquired muscles are not inherited and cannot be a factor in evolution, but mutations in DNA, the genetic code, are likely to be inherited and can play an important role in evolution.
Third, competition for survival among individuals occurs because resources are limited in the environment. If there are enough resources in the environment for all individuals to survive, both mutated and unmutated individuals will survive and the species will not change in a particular direction. The process of adaptation within an environment is accomplished through competition in a resource-limited environment. When the environment becomes saturated, intra-species competition for limited resources inevitably occurs.
Finally, the fourth condition is that individuals that have an advantage in survival leave more offspring. This process is called survival of the fittest through natural selection. Individuals that are adapted to their environment have a better chance of surviving intra-species competition and reproducing, which increases the number of offspring that carry their genes and mutations. This whole process is stochastic, and individuals that have a slight survival advantage through mutation will increase the number of individuals with the favorable trait over many generations.
Darwin’s argument was that through this process, populations adapt to their environment and change overall over time, and that the accumulation of these changes can eventually lead to the formation of new species.
Darwin’s theory of evolution was later combined with Mendel’s genetics to form Neo-Darwinism, which is now considered orthodoxy. August Weismann (1834-1914) refuted Lamarck’s arguments, which Darwin was unable to completely deny, and argued that evolution occurs solely through the process of natural selection. This theory evolved into the modern-day synthesis of Darwin’s theory of evolution by explaining it in terms of Mendelian inheritance. The core of this theory is the fact that traits are transmitted to the next generation by genes, which makes Darwin’s theory of evolution logically complete.
Another notable evolutionary theory is that of Richard Dawkins (1941-). His book, The Selfish Gene, has become an orthodoxy in academia and the general public since its publication. The core of Dawkins’ theory is that genes function as agents in the evolutionary process beyond reproduction and information transfer, and that individuals are merely vessels for carrying genes. Like Darwin’s theory of evolution, natural selection is the driving force behind evolution, but the key difference is that the agent of evolution shifts from individuals to genes. Dawkins’ perspective makes previously unexplained collective and altruistic behavior easier to understand. For example, worker bees or worker ants that are not reproductive and work for their queen may seem irrational on an individual level. However, given that they share the queen’s genes, their behavior can be explained as an effort to propagate their genes. Dawkins’ theory of evolution has gained widespread acceptance in the scientific community because it allows for the interpretation that these seemingly altruistic behaviors are actually calculated to increase the reproduction rate of the genes themselves.
One of the reasons evolutionary theory remains hypothetical despite its widespread acceptance is its controversy with creationists. For creationists and religious people, evolutionary theory is considered a sensitive topic and has been the subject of controversy. Some scientists even argue that evolutionary theory doesn’t provide a complete explanation for the great evolution. However, modern evolutionary theory explains that the great evolution can occur through countless microevolutions over a long period of time, leading to the differentiation of species. There are several other controversies that have led some to reject the theory of evolution.
Evolution is a theory that explains the diversity of species on Earth and how they have changed over time. The core of evolutionary theory is that species change through four principles: self-replication, mutation, environmental limitation, and natural selection. While evolutionary theory is often confronted with and questioned by creationism, it’s important to note that it explains a great deal of natural science and has the potential to explain even more in the future.
