The theory of evolution in biology does not provide an explanation for the origins of life on Earth. Nonetheless, it does shed light on the process through which life has evolved and diversified into different forms that currently exist and can be observed in the fossil record.
Biology helps us comprehend the existence of evolution in contemporary organisms and their continuous ability to adapt. In the field of biology, evolution is described as any changes in physical characteristics or instinctive behaviors within a population over generations. Instances of physical traits encompass the color of fur in mice, wing spots in butterflies, or instinctive behaviors such as how dogs greet their acquaintances through sniffing. This definition might be puzzling, so let’s delve into its functioning. All organisms, ranging from single-celled amoebas to flowers to dolphins, possess the capability to reproduce.
We reproduce by generating offspring, which includes replicating our DNA and transferring it to future generations. DNA is a chemical molecule contained in every cell of our bodies, offering instructions for growth and functionality. It contains encoded information that directs the formation of our beings.
Your DNA is distinct from that of a daffodil, thus explaining the variations in your physical and behavioral traits. Furthermore, your DNA differs slightly from other human beings, resulting in unique appearances and behaviors. Amoebas, simple organisms, reproduce by replicating their DNA within their stomachs and distributing the copies to opposite sides of their bodies. They then divide into two halves and eventually regrow to their original size. Ideally, these two new amoebas should be identical to each other. However, nature does not always ensure perfection.
During the process of copying DNA, mistakes can happen and alter the DNA code, resulting in a DNA mutation. These random and unintentional mutations can occur in any section of a DNA strand and lead to variations in the physical appearance and functioning of the organism inheriting the modified DNA. For example, our new acquaintance could possess an unusually elongated arm.
If he manages to survive and live long enough to grow and reproduce, his DNA will carry the code for an extended and flexible arm, which will subsequently be inherited by his offspring. This signifies that evolution, defined as any alteration in the inheritable characteristics of a population over successive generations, has taken place. However, the reproductive process for dolphins, badgers, and humans is more intricate as it necessitates the search for a suitable mate.
When two badgers engage in a romantic relationship and mate, the father’s sperm cell, which contains half of his DNA, merges with the mother’s egg cell, which also carries half of her DNA. As a result, a new cell is formed that possesses all the essential information required for division and development into a new badger. The offspring grows to resemble its parents while also inheriting distinct traits from both the mother and the father. These novel combinations of traits have the potential to be inherited by subsequent generations.
Evolution is the process of changes in heritable traits within a population over generations. In addition to inheriting traits from parents, individuals can also have new traits due to DNA mutations, like extremely furry ears. If they survive and reproduce, their DNA combines with their partner’s DNA, enabling them to pass on the hairy ear trait to some of their offspring.
Once again, it is official that evolution has taken place. Thus, evolution is undeniably a straightforward process. Both scientists and ordinary individuals witness the occurrence of evolution regularly. Gradual alterations, like the ones observed here, accumulate throughout generations resulting in significant transformations.
If you were to travel a few thousand years back, you would discover that all dogs, for instance, evolved from a common group of grey wolves. The evolution of these wolves occurred under human guidance, as people selectively bred wolves with favorable traits and kept only the puppies with the desired characteristics. As time progressed, various breeders developed preferences for dogs with distinct features.
Some selected from large size, some for small, some for brains, others for brawn. Today, wolves have diversified into hundreds of breeds, few of which resemble their ancestors in appearance or behavior. A substantial body of evidence from various fields, including genetics, chemistry, paleontology, and mathematics, strongly indicates that like all dogs share a common ancestor, all living beings – including humans, puffer fish, and banana trees – also share a common ancestor if we trace back far enough. We are essentially connected.
The diversity of life we witness today is believed to be a result of the reproduction process combined with variation over billions of years. Although it is unclear what the life form was or how it originated, evolution appears to be responsible. It may seem that evolution is random, but in order to achieve functional changes such as transforming a wolf into a cute miniature poodle, random evolution had to be intentionally guided by a knowledgeable dog breeder. Experts assert that all mammals evolved from a prehistoric creature resembling a shrew.
However, the distinction between a shrew and an elephant surpasses that of a wolf and a poodle. The question arises – who oversaw this development? Who acted as the breeder in this case? During the mid-1800s, Charles Darwin and Alfred Russell Wallace made individual observations, concluding that a breeder is not always necessary. They identified another force that can direct the progression of random evolution towards creating organization and intricate functionality. This phenomenon was labeled as natural selection.
Natural Selection is a crucial concept in the theory of evolution. Descent with Modification and Common Descent are two other important evolutionary concepts. Descent with modification refers to the observation that offspring differ slightly in appearance and behavior from their parents and siblings. This variation occurs as they descend from their parents.
Offspring vary because of random genetic mutations, but the concept of Common Descent proposes that all living creatures on Earth are connected and derived from a shared ancestor. This gradual process of descent with modification across generations is thought to have emerged from a solitary species and led to the diversity of life we presently witness.
The common descent of all life on earth cannot be directly observed due to the inability to travel back in time. Nevertheless, this assertion is backed by significant evidence from diverse fields including fossils, genetics, comparative anatomy, mathematics, biochemistry, and species distribution.
Despite being rejected by philosophers and scientists who believed that intricate order and behavior could not come from random chaos, the concept of common descent has been acknowledged since ancient times. However, the undeniable evidence in support of common descent makes it impossible to deny. Descent with modification is responsible for generating only arbitrary variations, despite the considerable complexity and organization exhibited by living organisms.
The mystery of the origins of complex life from simple life through random variation remained unsolved until Charles Darwin, a naturalist who lived from 1909-1882, discovered natural selection. During his journey around the world to collect and document plants and animals, Darwin developed a fascination with the concept of common descent.
The author noted that islands have their own distinct plants and animals that are exclusive to them. Nonetheless, these species often exhibit similar characteristics and behaviors to creatures found on nearby continents. For example, tortoises on the Galapagos Islands differ from those in Africa, but they closely resemble a species found in South America, with the exception of their size. Darwin proposed that these resemblances could be explained by Common Descent. According to this theory, a mainland tortoise could have floated to the islands, potentially on a raft made of storm debris, and subsequently laid its eggs upon arrival.
Over thousands of years, descent with modification has brought about random changes in both the island creatures and the mainland creatures, resulting in such significant transformations that they can no longer be classified as the same species. Darwin found this concept reasonable, except for one aspect: the island creatures he encountered were not merely randomly distinct; they were specifically adapted to thrive in their island habitats. The Galapagos is composed of eighteen main islands, several of which serve as habitats for tortoises. The larger islands boast abundant grass and vegetation.
On some islands, tortoises have developed dome-shaped shells and heavier bodies. These tortoises have adapted to survive on cactus plants due to the lack of grass. The top parts of the cactus are the most nutritious, but these tortoises can access them using their elongated necks, expanded front legs, and saddle-shaped shells.
The creatures on the island appear to have adapted to their environments with remarkable precision, similar to expert craftsmanship. The key inquiry is: what led to this adaptation? It can be attributed not only to arbitrary alterations and adjustments but also to Darwin’s comprehension of selective breeding. Over centuries, farmers have been altering wild plants and animals, resulting in new domestic variations that are more suitable for human objectives and consumption.
The process is simple but requires a lot of time. When a plant generates one hundred seeds, most of them will closely resemble the parent plant. However, a few seeds will show slight variations. While some differences may be undesirable, like smaller size, bitter taste, and vulnerability to disease, there will also be some highly attractive variations.
Thicker, sweeter leaves can be achieved by only allowing the best plants to reproduce and create seeds for the next crop. This practice leads to small positive changes that accumulate over multiple generations, ultimately resulting in a remarkably superior vegetable. It may come as a surprise, but broccoli, cabbage, cauliflower, kale, and Brussels sprouts are actually distinct breeds of a single type of weed commonly discovered along the shores of the English Channel. The transformation of this initial plant into the various varieties we observe today was skillfully directed by farmers worldwide who selectively favored different characteristics.
The farmer does not create anything; Random Descent with Modification generates new traits. The farmer’s role is to select which of these creations can reproduce and which cannot. According to Darwin, nature itself can also engage in selection.
Although lacking the intellect of a farmer, nature poses great threats to living beings. It harbors deadly germs and predatory animals that can cause harm. The extreme temperatures can lead to death from heat exhaustion or exposure to the cold. In the realm of nature, where survival is challenging, the traits of offspring determine their reproductive success as determined by nature.
Over multiple generations, creatures become better suited for survival and reproduction in their specific environments, a process known as Natural Selection, as coined by Darwin in the mid-1800s. Since its proposal, natural selection has been extensively studied and observed in both nature and scientific laboratories. What was once just an idea has now been firmly established as an observable fact.
Darwin’s remarkable finding has significantly deepened our comprehension of the natural world, leading to numerous groundbreaking achievements and enabling scientists to genuinely contemplate the notion of Common Descent.
