At first glance, the title evokes thoughts of Charles Darwin and his book The Origin of Species. Upon closer examination, it becomes clear that this article explores the concepts of evolution, natural selection, and, more specifically, how species adapt and survive.
Charles Robert Darwin (1809–1882) was an English geologist, biologist, and naturalist renowned for his groundbreaking contributions to evolutionary biology. Rather than focusing on his medical studies at Edinburgh University, which he began in 1825, Darwin, a curious youth, immersed himself in various fields of knowledge.
With Professor Robert Edmund Grant, Darwin collected sea slugs and sea pens along the shore, where his mentor explained the growth and relationships of primitive marine invertebrates. These studies provide insight into the origins of more complex forms of life.
Darwin, a free-spirited naturalist, later attended Christ’s College, Cambridge, in 1828, where he developed an interest in activities such as riding, drinking, and shooting. Eventually, he earned a Bachelor of Arts degree in 1831, a prerequisite for entering divinity studies and becoming an Anglican parson.
During this time, Darwin developed a strong connection with the conservative side of botany through Professor John Stevens Henslow. Henslow later recommended that Darwin join him on the voyage aboard HMS Beagle, which set sail on 27 December 1831.
During the journey, Darwin collected numerous specimens of flora, fauna, and fossils, amassing vast amounts of first-hand knowledge about various species. One of the most significant stops on the journey was the Galapagos Islands, a living laboratory teeming with unique species. These islands were integral to the development of Darwin’s theory of evolution.
The islands were home to volcanic landscapes, giant tortoises, and marine iguanas. During his five-week stay, Darwin observed 17 to 18 species of small, sparrow-like birds. These birds, now famously known as “Darwin’s finches”, each had distinct beak shapes suited to specific feeding needs. Darwin concluded that species adapt to their environment to secure food, shelter, and safety in response to predators, climate, and other factors.
Evolution
Evolution is the process by which different kinds of living organisms are believed to have developed from earlier forms throughout Earth’s history.
Types of Evolution
- Divergent Evolution: Occurs when a single species splits into multiple species. Darwin’s finches are an example.
- Convergent Evolution: Happens when different species develop similar traits due to similar environmental pressures. For instance, hummingbirds and hummingbird moths exhibit similarities despite being unrelated.
- Coevolution: Involves two species influencing each other’s adaptations.
- Parallel Evolution: Occurs when different species with similar ancestors maintain comparable traits due to similar environments.
- Gradualism: Describes how species slowly diverge over long periods, sometimes taking millions of years.
- Punctuated Equilibrium: Refers to sudden bursts of evolution, leading to the rapid emergence of new species.
Natural Selection
Natural selection is a key mechanism of evolution. Individuals with traits better suited to their environment are more likely to survive and reproduce, passing on these advantageous traits to the next generation. It is a process by which random evolutionary changes are selected for by nature in a consistent, non-random manner.
Types of Natural Selection
- Directional Selection: For example, giraffes with taller heights are favoured because they can better access food on higher branches, meaning the extreme trait—tall height—is selected.
- Stabilising Selection: In a population of turtles, medium-sized shells may be favoured because smaller turtles are eaten too quickly, and larger turtles struggle to access food in coral reefs. Hence, the intermediate trait (medium shell size) is most beneficial.
- Disruptive Selection: If both small and large turtles are favoured while medium-sized turtles are preyed upon, this would be an example of disruptive selection, where both extreme traits are advantageous.
- Sexual Selection: Peacocks’ colourful tails are an example of sexual selection, where traits evolve to attract mates, increasing reproductive success.
Survival of the Fittest
The term “survival of the fittest” was coined by English sociologist and philosopher Herbert Spencer in his 1864 book Principles of Biology. Darwin adopted this phrase in the fifth edition of his publication in 1869, noting that Spencer had aptly expressed the concept of natural selection.
The 1858 Darwin-Wallace Paper
It is important to note that Darwin did not fully understand the role of genes in evolution. However, in 1858, Darwin and Alfred Russel Wallace, independent thinkers unknown to one another, jointly published their first paper on evolution.
Histoire Naturelle and Buffon’s Influence
While we often associate evolution with Darwin, he later discovered that Georges-Louis Leclerc, Comte de Buffon, had made significant contributions 100 years prior. Upon reading Buffon’s Histoire Naturelle, Darwin realised that many of Buffon’s ideas mirrored his own.
Buffon proposed that animals were going extinct, challenging the belief of the time that God did not allow species to vanish. Buffon theorised that reproduction followed an “inner mould” that organised specific building blocks into particular organisms. This concept, though ahead of its time, could be interpreted as an anticipation of DNA’s role in inheritance.
Buffon’s ideas, although controversial, influenced subsequent scientists, including Jean-Baptiste Lamarck and Georges Cuvier.
Conclusion
Species evolve by adapting to their changing environments to survive and flourish. In today’s world, the focus is no longer solely on competition for survival but also on ensuring that species coexist and thrive together. As National Geographic puts it, “Today, human actions such as overhunting and habitat destruction are the main causes of extinction, occurring at a much faster rate than in the past, as shown in the fossil record.”
