The Doctrine Of Evolution: Its Basis And Its Scope Informative Summary


The Doctrine of Evolution is a scientific framework for understanding the history and current state of the natural world, including living organisms. It argues that natural processes operating today have also shaped the past, including the evolution of life. This lecture series explores the evidence for evolution, focusing on the remarkable diversity and interconnectedness of life, and how the human species fits into this grand scheme.

The lectures begin by examining the fundamental characteristics of living organisms, emphasizing their mechanical nature and adaptation to their environment. The series then delves into the evidence for evolution from various fields of natural history, including comparative anatomy, embryology, paleontology, and geographic distribution. Each discipline provides unique insights into the interconnectedness of life and the transformations that have occurred over time.

Key Findings:

  • The principle of adaptation is central to the understanding of life’s diversity. Organisms are intricately designed to suit their specific environments and needs.
  • The unity of life is evident in shared structural plans, developmental patterns, and fossil histories. Organisms, despite their apparent differences, are connected through common ancestry.
  • Darwin’s theory of natural selection provides a plausible explanation for the mechanisms of evolution. Variation, overproduction, and competition drive the selection of traits that enhance survival and reproduction.
  • Human beings are not exempt from the laws of evolution. Our physical structure, mental abilities, and social organization are products of a long history of natural transformation.
  • The human species is not unique. Our closest relatives are the apes, with whom we share a common ancestor, and whose evolutionary history provides valuable insight into our own.
  • Different human races have evolved along separate branches, displaying distinct characteristics, but also retaining a shared lineage.


  • Adaptation: Living organisms are intricately designed to suit their specific environments and needs. This adaptation arises through a process of trial and error, where advantageous traits are selected for by natural forces.
  • Variation: No two organisms are exactly alike, and these variations are driven by three primary factors: environmental influences, functional use and disuse, and congenital inheritance.
  • Inheritance: Congenital traits, determined by the germ plasm within the nucleus of cells, are passed down through generations. This principle explains why acquired characteristics are not inherited.
  • Natural Selection: The process of natural selection favors organisms with advantageous traits that enhance survival and reproduction. Overproduction and competition ensure that only the most fit individuals pass their traits on.
  • Human Evolution: The human species is a product of natural evolution, sharing a common ancestor with apes. We have evolved a highly developed brain, which has led to our advanced intelligence, social organization, and ability to reason.
  • Human Races: Different human races have evolved along separate branches, displaying distinct characteristics. However, all races share a common ancestry and are connected through a continuous process of evolution.
  • Mental Evolution: Our mental abilities, from instinct and intelligence to reason, are the products of a long evolutionary history. This progression is evident in both individual development and the historical evolution of human thought.
  • Social Evolution: Human societies have evolved from simple family units to complex, interconnected civilizations. This evolution is driven by the same principles of combination and differentiation that operate in other biological communities.
  • Ethics and Religion: Ethical principles and religious beliefs have evolved along with human societies. The fundamental elements of religion—belief in God, human responsibility, and immortality—can be explained through natural processes, arising from human psychology, the desire to survive, and the need to find meaning in a complex world.

Historical Context:

The doctrine of evolution was first formally proposed in the 19th century, built upon previous ideas about change and natural processes. Lyell’s uniformitarianism theory, arguing that the same natural forces shaping the Earth today were active in the past, provided a crucial foundation for Darwin’s theory of natural selection.


  1. The Earth was once a molten mass, a part of a larger nebulous material, that eventually condensed to form the planets of our solar system. (This is true due to the natural processes of cooling and condensation, which are observed in the formation of stars and planets.)
  2. Organic evolution begins with life, and is a part of the greater cosmic process. (Life arose from the non-living world through a process not fully understood by science, but once present, began to evolve.)
  3. The first steam locomotive was a crude mechanism compared to modern trains. (The evolution of technology is a human process of trial and error, similar to natural selection.)
  4. Living organisms are “devices for transforming and utilizing energy.” (Like machines, organisms take in energy from their environment and transform it for their own use.)
  5. Living things have a definite and restricted chemical composition. (The primary building blocks of life are a specific set of chemical elements, mostly carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus.)
  6. The cell is the fundamental unit of life. (All organisms are composed of cells, and complex organisms begin their development as single cells.)
  7. A living organism is a temporary aggregate of elements that pass back and forth between the living and non-living world. (Organisms are constantly taking in matter and energy from their environment and releasing it as waste.)
  8. The process of oxidation, which fuels the burning of a candle, is the same for the living cell. (The fundamental processes of life are ultimately based on chemical reactions.)
  9. Science cannot prove or disprove the existence of a “vitalistic principle” that animates living matter. (The search for a “life force” beyond physical and chemical processes has not yielded conclusive evidence.)
  10. A rudimentary structure, like the cowcatcher on a train, can persist even when its original function is lost. (Vestigial structures, often reduced or non-functional, reveal clues about an organism’s evolutionary history.)
  11. The bones of the fore limb of a whale are the same as those of a cat’s leg, though they are adapted for swimming. (Homologous structures, with common ancestry, are often modified for different functions.)
  12. The evolution of the whale from land-dwelling ancestors is supported by the presence of tiny, non-functional hind limbs. (Vestigial organs can indicate the past history of an organism.)
  13. The duckbill and echidna, egg-laying mammals, demonstrate a connection between mammals and reptiles. (These “primitive” mammals retain features of their reptilian ancestors.)
  14. The most reasonable interpretation of the similar early stages in the development of diverse vertebrates is a common ancestry. (Ontogeny recapitulates phylogeny, meaning that the development of an organism reflects its evolutionary history.)
  15. Fossils are not created as fragments, but are remnants of organisms that lived in the past. (Fossils provide direct evidence of past life forms.)
  16. The Earth has been shaped by slow, continuous geological processes, not by catastrophic events. (The uniformitarianism theory is supported by evidence of erosion and sedimentation.)
  17. The majority of the oldest sedimentary rocks are devoid of fossils. (The lack of fossils in the earliest layers is due to the lack of hard parts in primitive organisms and the transformation of the original rock layers.)
  18. The earliest true horses had four toes on their forefeet and three on their hindfeet. (Fossil evidence reveals the gradual reduction of toes in the horse lineage.)
  19. Archæopteryx, with its feathered wings and reptilian jaws, provides a link between birds and reptiles. (Transitional fossils demonstrate the gradual development of new species.)
  20. Species on islands often resemble those on the nearest mainland, indicating migration and subsequent evolution. (Geographic isolation can lead to the formation of unique species.)


  1. The Mississippi River basin, covering about one-third of the United States, loses an average of one foot of soil and rock every 6000 years. (This demonstrates the immense power of erosion over long periods.)
  2. The Mississippi River discharges enough sediment to cover one square mile to the depth of 269 feet every year. (This showcases the vast amount of material transported by rivers.)
  3. The Niagara Falls have receded an average of 104 inches per year since 1843. (This provides a concrete example of the rate of erosion.)
  4. The Grand Cañon of the Colorado is over a mile deep and 200 miles long. (This shows the immense scale of geological processes over time.)
  5. Volcanoes in the Java region have erupted over 100 cubic miles of lava, cinders, and ashes in the last 100 years. (This illustrates the dramatic impact of volcanic activity.)
  6. The oldest sedimentary rocks, the Azoic or Archæan, comprise about 30,000 feet of strata, which may have taken 20,000,000 years to form. (This provides a scale for the vast timescale of geological history.)
  7. The Palæozoic age, encompassing about 106,000 feet of strata, took roughly 21,000,000 years to deposit. (This gives a sense of the long time spans over which evolution has occurred.)
  8. The English sparrow, introduced to North America less than 50 years ago, has multiplied rapidly, illustrating its high reproductive rate. (The unchecked growth of populations showcases the importance of natural checks on population size.)
  9. A single conger eel can produce 15 million eggs in a season. (This highlights the immense reproductive potential of many species.)
  10. A single tapeworm can produce 300 million embryos. (This exemplifies the enormous reproductive capacity of some organisms.)
  11. The descendants of a single bacterium can fill all the oceans to the depth of one mile within five days, under ideal conditions. (This shows the incredible growth rate of some microorganisms.)
  12. The human species has doubled in the last 25 years. (This highlights the rapid growth of the human population.)
  13. A pair of elephants can produce 19 million offspring within 800 years, under ideal conditions. (This illustrates the potential for rapid population growth, even in slow-breeding species.)
  14. The average height of humans varies from 4 feet 1 inch to nearly 6 feet 7 inches, across different races. (This showcases the wide range of physical variation within the human species.)
  15. The brain capacity of humans varies from 900 cubic centimeters to 2200 cubic centimeters. (This demonstrates the wide range of brain size across individuals.)
  16. The “blackfellow” of Australia has a low brain capacity of about 900 cubic centimeters. (This highlights the variation in brain size among different races.)
  17. The chimpanzee’s mental ability is comparable to that of a nine-month-old human infant. (This shows that apes possess a level of intelligence similar to human infants.)
  18. The brain of a six-month-old human infant is comparable to that of a well-bred fox terrier. (This highlights the development of intelligence in infants.)
  19. The average stature of the Northern European is about 5 feet 8 inches tall. (This gives a specific example of racial differences in body size.)
  20. The average height of the Mongol is about 5 feet 4 inches tall. (This illustrates the variation in stature across different races.)


  1. Adaptation: The process by which organisms become better suited to their environment.
  2. Variation: The natural differences that exist between individuals within a species.
  3. Inheritance: The transmission of traits from parents to offspring.
  4. Natural Selection: The process by which organisms with advantageous traits are more likely to survive and reproduce.
  5. Overproduction: The tendency of organisms to produce more offspring than can survive.
  6. Competition: The struggle for resources, mates, and survival among organisms.
  7. Vestigial Structure: A remnant of an anatomical feature that was present in an organism’s ancestors but has lost its function.
  8. Homologous Structures: Structures with a common ancestry, often adapted for different functions.
  9. Ontogeny: The development of an organism from a single cell to its adult form.
  10. Phylogeny: The evolutionary history of a species or group of organisms.


  1. Locomotion: The evolution of the whale from a land-dwelling ancestor to a marine animal with flippers is a prime example of adaptation.
  2. Vestigial Structures: The tiny, non-functional hind limbs of a whale are a remnant of its four-legged ancestors.
  3. Ontogeny recapitulates phylogeny: The development of a chick includes a stage with gill-slits, reflecting its evolutionary history from fishlike ancestors.
  4. Natural Selection: The English sparrow, introduced to North America, has thrived because it lacked its natural predators and could compete successfully for resources.
  5. Artificial Selection: The breeding of race horses for speed and of cattle for milk production demonstrate how humans can select for desired traits.
  6. Human Evolution: The similarity in skeletal structure and developmental patterns between humans and apes is strong evidence for a common ancestor.
  7. Human Races: The Mongolians, with their straight black hair and slanted eyes, represent a distinct racial type that has evolved along a separate branch from the Caucasian race.
  8. Mental Evolution: The development of a human infant, from exhibiting simple reflexes to demonstrating complex reasoning abilities, is a clear example of mental evolution.
  9. Social Evolution: The development of beehives, with their specialized castes of queen, drones, and workers, highlights the evolution of complex social organization in insects.
  10. Ethics: The practice of infanticide, once common in some cultures, demonstrates how ethical norms can evolve as societies change.


The Doctrine of Evolution offers a powerful framework for understanding the history and interconnectedness of all life, including human beings. It presents a compelling and consistent explanation for the diversity of life, the transformations that have occurred over time, and the origin of human traits and social structures. Evolution is a continuous process, driven by natural forces, and its insights have profound implications for our understanding of ourselves, our place in the world, and our responsibilities to each other. While the doctrine itself does not dictate our beliefs or actions, it provides a valuable foundation for making informed choices and contributing to the betterment of humanity.

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