History of Evolutionary Thought: Videos & Practice Problems

Charles Darwin and Alfred Russel Wallace independently formulated the theory of evolution by natural selection in the mid-1800s. Darwin's observations during his voyage on the HMS Beagle, particularly in the Galapagos Islands, led him to conclude that species adapt to their environments over time. Wallace, through his studies in the Malay Archipelago, identified similar patterns of species distribution. Both naturalists emphasized the role of environmental pressures in shaping adaptations, laying the groundwork for modern evolutionary biology and the understanding of genetic variation as a key factor in evolution.

Geological Thinking

Before delving into Charles Darwin's theory of evolution by natural selection, it's essential to understand the scientific context of his time, particularly the shift in geological thought during the late 1700s. Prior to this period, the prevailing belief, influenced by philosophers like Plato and Aristotle, was that species were unchanging and organized in a hierarchical structure known as the Great Chain of Being. However, advancements in geology began to challenge these notions.

Three key figures emerged during this transformative period: James Hutton, Georges Cuvier, and Charles Lyell. James Hutton introduced the concept of uniformitarianism, which posits that the geological processes we observe today, such as erosion and sedimentation, have been consistent throughout Earth's history. This idea implies that the Earth is very old, as the formation of significant geological features, like mountains and canyons, requires extensive time and gradual change.

Georges Cuvier, a prominent paleontologist, contributed to our understanding of extinct species through his study of fossils. He argued that the fossil record demonstrates that many organisms, such as the trilobite and giant ground sloths, no longer exist, indicating that life on Earth has changed over time. Although Cuvier believed species were fixed and did not evolve, his recognition of extinction opened the door to the possibility of species change.

In the early 1800s, Charles Lyell synthesized these ideas in his influential work, Principles of Geology. This book popularized modern geological thought and was significant for Darwin, as he carried it on his voyage aboard the HMS Beagle. Lyell's work emphasized the slow, gradual processes shaping the Earth, reinforcing the notion of an ancient planet.

In summary, the contributions of Hutton, Cuvier, and Lyell laid the groundwork for Darwin's revolutionary ideas. Hutton's uniformitarianism highlighted the slow pace of geological change, Cuvier's fossil studies revealed the reality of extinction, and Lyell's writings provided a comprehensive framework for understanding Earth's history. Together, these concepts set the stage for the development of evolutionary theory.

Whose book “Principles of Geology” most directly influenced the thinking of Charles Darwin?

• A. Georges Cuvier.
• B. Charles Lyell.
• C. Alfred Russel Wallace.
• D. James Hutton.

Answer: (B)

Which scientist was one of the first proponents of uniformitarianism and suggested the Earth was much older than a few thousand years?

• A. Georges Cuvier.
• B. Charles Lyell.
• C. Alfred Russel Wallace.
• D. James Hutton.

Answer: (D)

Which scientist specialized in fossils and has been called “The Father of Paleontology”?

• A. Georges Cuvier.
• B. Charles Lyell.
• C. Alfred Russel Wallace.
• D. James Hutton.

Answer: (A)

Lamarck and Inheritance of Acquired Traits

By the early 1800s, the field of geology was beginning to embrace the concept of a changing Earth, while biological thought was still grappling with the mechanisms of evolution. During this period, Jean Baptiste Lamarck emerged as a significant figure, proposing one of the first mechanisms for evolution through his theory of the inheritance of acquired traits. Although there was growing evidence for evolution, scientists lacked a comprehensive explanation for how species changed over time, primarily due to the absence of an understanding of genetics until the early 1900s.

Lamarck's theory was based on two key principles. The first principle, known as use and disuse, suggested that traits could become more or less developed during an organism's lifetime based on their usage. For instance, if an individual consistently exercised one arm, that arm would become stronger, while the other might weaken due to lack of use. These changes within a lifetime were termed acquired traits.

The second principle, which is where Lamarck's theory falters, posited that these acquired traits could be inherited by the next generation. For example, he theorized that if a kangaroo ancestor developed larger hind limbs due to jumping, its offspring would inherit these larger limbs, while the forelimbs would be smaller due to disuse. This notion of inheriting traits acquired during an organism's life is fundamentally incorrect, as modern genetics shows that only genetic variations are passed down to offspring, not traits developed through individual experience.

In summary, while Lamarck's ideas contributed to the early discussions of evolution, they were ultimately flawed. The changes that occur during an organism's lifetime do not affect the genetic information passed to the next generation. Today, we understand that evolution is driven by genetic variation and natural selection, concepts that were not fully appreciated until the rediscovery of Mendel's work in the early 20th century.

History of Evolutionary Theory Example 1

The fiddler crab exhibits a fascinating characteristic of having one large claw and one small claw, which can be examined through the lens of Lamarckian evolution. According to Lamarck's principles, particularly the concepts of use and disuse and the inheritance of acquired traits, one might hypothesize that the crab originally had claws of equal size. Over time, as the crab utilized one claw more frequently, that claw would grow larger due to its increased use, while the less-used claw would diminish in size due to disuse.

Lamarck would suggest that this change in claw size could be passed down to the crab's offspring, resulting in the next generation inheriting one large claw and one small claw. However, it is crucial to recognize that Lamarck's theories have been largely discredited in modern biology. The principle of use and disuse does not universally apply, as not all traits are enhanced or diminished through usage. More importantly, the idea of the inheritance of acquired traits is fundamentally incorrect; traits acquired during an organism's lifetime are not genetically passed on to future generations.

Today, evolutionary biology emphasizes genetic variation as the primary driver of evolution, rather than changes that occur within an individual's lifetime. Understanding these distinctions is essential for grasping the mechanisms of evolution and the role of genetic inheritance in shaping species over time.

Lamarck developed his ideas almost 100 years before Mendel’s principles of genetics would be widely understood. With our current understanding of genetics, which of Lamarck’s ideas do we most clearly understand to be INCORRECT?

• A. In an individual, traits that are not used regularly will become less enhanced.
• B. In an individual, traits that are used regularly will become more enhanced.
• C. Characters acquired in an organism’s lifetime can be inherited by offspring.
• D. Populations will become more adapted to their environments over time.

Answer: (C)

Certain dog breeds regularly have “docked” tails, where a dog’s tail is cut to a short length while still a puppy. A breeder of rottweilers tells you that docking has become so common in this breed that they think puppies will start being born with short tails. Evaluate their thinking.

• A. Because only dogs with docked tails are reproducing, puppies are likely to be born with short tails.
• B. A docked tail would be considered an acquired trait, and therefore, you would not expect it to be inherited.
• C. Docked tails will become more common if they help the dogs perform certain tasks.
• D. Short tails are unlikely to become common in puppies because a docked tail mainly affects a dog’s appearance.

Answer: (B)

Darwin and Wallace

Charles Darwin and Alfred Russel Wallace are pivotal figures in the development of the theory of evolution by natural selection, both arriving at similar conclusions in the mid-1800s. Darwin, born in 1809 into a wealthy intellectual family, initially pursued a career in medicine but shifted to theology, ultimately finding his passion in studying nature. His transformative journey began in 1831 when he joined the HMS Beagle as a naturalist, embarking on a significant expedition to South America.

During this voyage, Darwin made crucial observations, including the discovery of fossils and the unique organisms of the Galapagos Islands, such as Darwin's finches and marine iguanas. These experiences led him to hypothesize that species adapt to their environments over time, a concept influenced by the geological theories of Hutton and Lyell. Upon returning to England, Darwin spent over 20 years refining his ideas, aware of the potential controversy they might incite.

In 1858, Darwin received a letter from Wallace, who had independently developed a similar theory. Wallace, a less formally educated naturalist, had spent years collecting specimens in the Amazon and the Malay Archipelago, where he noted distinct species distributions that suggested evolutionary processes. His observations led to the formulation of what is now known as Wallace's Line, illustrating the divergence of species based on geographical boundaries.

Upon realizing that Wallace had reached the same conclusions, Darwin quickly prepared a paper that was presented alongside Wallace's findings. This collaboration culminated in the publication of Darwin's seminal work, "On the Origin of Species," which provided extensive documentation and evidence for the theory of evolution by natural selection. While Darwin's contributions are often highlighted, it is essential to acknowledge Wallace's role in the development of this groundbreaking scientific theory.

In summary, the theory of evolution by natural selection emerged from the combined efforts of Darwin and Wallace, both of whom made significant contributions through their observations and research. Their work laid the foundation for modern evolutionary biology, emphasizing the importance of adaptation and the interconnectedness of life on Earth.

Of the following four observations, three were made by and strongly influenced Charles Darwin. Which observation was made by and influenced Alfred Russel Wallace?

• A. The distribution of species on islands in the Malay Archipelago.
• B. A large earthquake in Chile that caused measurable changes to the landscape.
• C. Fossils, including those of an extinct giant ground sloth.
• D. Differences between the finches on different islands of the Galapagos.

Answer: (A)

In 1858, Darwin received a letter from Alfred Russel Wallace describing a theory nearly identical to his theory of natural selection. How did Darwin respond?

• A. He ignored the letter and quickly published his own short paper.
• B. He immediately published his book “On the Origin of Species”.
• C. He quickly published his own paper jointly with Wallace’s letter.
• D. He published the letter from Wallace first, and waited to publish his ideas until he had finished his book “On the Origin of Species”.

Answer: (C)

Here’s what students ask on this topic:

What were the key contributions of James Hutton, Georges Cuvier, and Charles Lyell to the field of geology?

James Hutton introduced the idea of uniformitarianism, which posits that geological processes occurring today are the same as those in the past, implying that Earth is very old. Georges Cuvier, considered the father of modern paleontology, studied fossils and argued that the fossil record shows extinct organisms, indicating that life today is different from the past. Charles Lyell modernized these ideas and popularized them in his book 'Principles of Geology,' which was influential in the scientific community and particularly for Charles Darwin. Together, their contributions laid the groundwork for understanding Earth's geological history and the concept of an evolving planet.

How did Jean-Baptiste Lamarck's theory of evolution differ from Darwin's theory of natural selection?

Jean-Baptiste Lamarck proposed that traits acquired during an organism's lifetime through use or disuse could be inherited by its offspring, a concept known as the inheritance of acquired traits. For example, he suggested that a kangaroo's strong hind limbs developed from jumping and would be passed on to its offspring. In contrast, Charles Darwin's theory of natural selection posited that individuals with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to the next generation. Darwin's theory is based on genetic variation and differential survival, not the inheritance of acquired traits.

What observations did Charles Darwin make during his voyage on the HMS Beagle that contributed to his theory of evolution?

During his voyage on the HMS Beagle, Charles Darwin made several key observations that contributed to his theory of evolution. In South America, he observed fossils of extinct species like the giant ground sloth, noting differences between past and present life forms. In Chile, he witnessed an earthquake that demonstrated geological changes. Most famously, in the Galapagos Islands, he observed unique species such as finches with varying beak shapes and marine iguanas, which led him to conclude that species adapt to their environments over time. These observations helped him formulate the idea of natural selection as a mechanism for evolution.

How did Alfred Russel Wallace's studies in the Malay Archipelago contribute to the theory of evolution by natural selection?

Alfred Russel Wallace's studies in the Malay Archipelago significantly contributed to the theory of evolution by natural selection. He observed distinct patterns of species distribution, noting that organisms on islands to the south and east of the Wallace Line resembled Australian species, while those to the north and west were more like Asian species. This led him to hypothesize that species evolve and adapt to their environments over time. Wallace's independent formulation of the theory, based on his extensive fieldwork and observations, paralleled Darwin's conclusions and prompted the joint publication of their ideas, solidifying the foundation of evolutionary biology.

Why is Charles Darwin often more credited with the theory of evolution by natural selection than Alfred Russel Wallace?

Charles Darwin is often more credited with the theory of evolution by natural selection than Alfred Russel Wallace primarily because of Darwin's extensive research and the publication of his influential book, 'On the Origin of Species.' Darwin spent over 20 years gathering evidence and developing his theory, which he meticulously documented in his book. This comprehensive work had a significant impact on both the scientific community and the public. Although Wallace independently arrived at similar conclusions and co-published the initial paper with Darwin, Darwin's detailed and well-supported exposition in 'On the Origin of Species' solidified his association with the theory.