Darwinism Informative Summary


This book, written by Alfred Russel Wallace, a contemporary and co-discoverer of natural selection with Darwin, provides a detailed exploration of the theory of natural selection. The book argues that natural selection, driven by the struggle for existence and the inherent variability of organisms, is the primary force behind the origin of new species. Wallace builds upon Darwin’s work, incorporating new findings and addressing critiques that arose in the years following the publication of “On the Origin of Species.”

The first few chapters lay the foundation for the theory, examining the concepts of species, the struggle for existence, and the variability of both wild and domesticated organisms. Wallace presents evidence to demonstrate the tremendous rate at which organisms reproduce and the resulting competition for limited resources. He also showcases the extensive and often significant variation that exists within species, even among those in their natural state. He further emphasizes the power of artificial selection, showcasing how humans have successfully modified domesticated animals and cultivated plants through careful selection of desirable traits

The subsequent chapters delve into the mechanisms of natural selection, exploring how variations that enhance an organism’s ability to survive and reproduce are selected for and propagated through generations. This process leads to the diversification of species, with each adapting to its unique environmental niche. Wallace addresses numerous objections raised against natural selection, including the issue of small variations, the emergence of complex organs, and the swamping effects of interbreeding. He further examines the intricacies of hybridity, questioning the dogma of universal sterility in hybrids and fertility in mongrels, and presenting evidence that supports the role of natural selection in influencing fertility.

The final chapters move beyond the mechanics of evolution, exploring the origins and uses of color in animals, examining both protective coloration and mimicry. Wallace provides evidence for the function of color in concealing animals from predators, in attracting prey, and in facilitating communication and recognition among members of the same species. He also delves into sexual selection, challenging Darwin’s theory of female choice and proposing alternative explanations for the development of ornamental plumage in birds and other animals.

The book concludes with a discussion of the origin of man, examining the anatomical and developmental evidence that connects humans to other primates, particularly the anthropoid apes. Wallace argues for a common ancestor for humans and the apes, and speculates about the possible birthplace of mankind and the early stages of human evolution. He then goes on to address the origins of human intellect and moral sense, questioning whether these faculties were solely shaped by natural selection.

Key Findings:

  • Natural selection is the primary force behind the origin of new species. It acts by favoring those variations that enhance an organism’s survival and reproductive success.
  • Species are not fixed but are constantly evolving and adapting. They are not immutable creations, but rather the product of a long process of descent with modification.
  • Variation is a pervasive feature of all species. It is not limited to superficial traits, but can also affect internal organs, anatomical features, and even habits and behaviors.
  • Interbreeding can be a powerful force in shaping populations. While intercrossing between different species often results in infertility or sterility, careful selection can sometimes lead to fertile hybrid offspring.
  • Color plays a vital role in the survival and reproduction of organisms. It serves as a means of camouflage, warning, recognition, and attraction.
  • The human body shows a close anatomical and developmental relationship to other mammals, particularly the anthropoid apes.
  • Human intellect and moral sense likely arose through a combination of natural selection and other, perhaps spiritual, influences.


  • The reader will learn about the process of natural selection. They will understand how the struggle for existence, coupled with variation, leads to the survival and propagation of those organisms best suited to their environment.
  • The reader will gain a deeper understanding of species and their origins. The book challenges the notion of fixed species and demonstrates how the theory of evolution accounts for the immense diversity of life on Earth.
  • The reader will learn about the importance of variation in evolution. They will see how variations, both small and large, provide the raw material for natural selection to act upon.
  • The reader will explore the diverse uses of color in the animal world. The book reveals how color serves a multitude of functions, including camouflage, warning, mimicry, and communication.
  • The reader will gain insights into the origins of human evolution and the nature of human intellect. The book raises questions about the limitations of natural selection in explaining the emergence of human consciousness and advanced cognitive abilities.

Historical context:

  • The book was written in 1889, following decades of debate and discussion about Darwin’s theory of evolution.
  • Wallace’s book reflects the growing acceptance of the principle of descent with modification, but also highlights the ongoing critiques and challenges to Darwin’s theory, particularly in relation to the role of natural selection in shaping complex adaptations and human intellect.


  1. Species are not immutable. They change over time due to natural selection.
  2. All organisms have the potential to reproduce rapidly. This leads to competition for resources, known as the struggle for existence.
  3. Variation exists within every species. Individuals within a species differ in traits like size, color, and behavior.
  4. Favorable variations are passed on to offspring. This process is known as natural selection.
  5. Natural selection leads to the diversification of species. As species adapt to their environments, they become increasingly different.
  6. Most species are capable of interbreeding with closely related species. However, this often results in infertile or sterile offspring.
  7. Color plays a crucial role in animal survival. It can be used for camouflage, warning, mimicry, and communication.
  8. The human body exhibits numerous anatomical features that link it to other mammals. These include rudimentary organs and muscle variations.
  9. The human embryo undergoes stages of development that mirror those of other mammals. This is further evidence of shared ancestry.
  10. Many diseases are shared between humans and other animals. This indicates a similarity in their biological structures.
  11. The anthropoid apes are the most closely related animals to humans. However, there is no single species that can be definitively identified as our closest relative.
  12. The brain of humans is significantly larger and more complex than the brains of apes.
  13. The human foot is uniquely adapted for upright walking. Apes retain a grasping foot that resembles a hand.
  14. The mathematical faculty is nearly absent in most savage tribes. This suggests it is a relatively recent development in human evolution.
  15. The musical and artistic faculties also appear to be late developments in human evolution. They are not essential for survival, and are only prominent in a small percentage of the population.
  16. The development of human intellect, including complex cognitive abilities and moral sense, likely involves factors beyond natural selection. This points to the possibility of a spiritual element in human nature.
  17. The earliest known human remains date back to the late Pleistocene era. There is limited evidence of human existence during the Pliocene era.
  18. The probable birthplace of mankind is thought to be in the Eastern hemisphere. The large plateaus of Asia may have provided the ideal environment for early human development.
  19. The diversity of human skin color likely arose in response to different environmental conditions. This suggests a close correlation between skin pigmentation and physiological adaptations.
  20. The development of human culture, technology, and language have allowed humans to adapt to a wider range of environments than other animals. This has freed humans from the direct pressures of natural selection on their physical bodies, allowing for the rapid evolution of their intellect.


  1. The number of known fossil molluscs exceeds the number of living species. This highlights the vastness of the fossil record and the constant change in species over geological time.
  2. The land area of the Earth is about 28% of the total surface. The remaining 72% is covered by water.
  3. The average height of land above sea level is about 2250 feet. The average depth of the ocean is about 14,640 feet.
  4. The volume of dry land is about 23,450,000 cubic miles. The volume of water in the oceans is about 323,800,000 cubic miles.
  5. The thousand-fathom line marks a probable boundary between continental and oceanic areas.
  6. The Mozambique Channel, which separates Madagascar from Africa, is deeper than 1000 fathoms. This suggests a long history of separation.
  7. The sea separating New Zealand from Australia is more than 2000 fathoms deep. This reinforces the idea of their ancient separation.
  8. The remains of over 40 species of beasts of prey alone were found in a limited area in Quercy, France. This highlights the abundance of past biodiversity.
  9. Over 30 species of fossil Equidae have been discovered in the United States. This extensive fossil record showcases the gradual evolution of the horse.
  10. The Irish elk, possessing the largest antlers ever known, became extinct during the prehistoric era. This demonstrates that even highly successful species can become extinct due to environmental changes.
  11. The average human brain weighs 48-49 ounces. This is significantly larger than the average ape brain, which weighs about 18 ounces.
  12. Over 558 muscular variations were observed in 36 human subjects. This highlights the significant variability in human anatomy.
  13. Around 8,000 to 9,000 species of fossil plants have been described. This demonstrates the diversity of past plant life.
  14. About 3,000 species of ferns are currently known. This is significantly higher than the number of fossil fern species found in the Miocene era.
  15. Over 770 species of dicotyledonous flowering plants are found in the Upper Cretaceous period. This marks the rapid diversification of the angiosperms.
  16. Insects are found at altitudes of up to 18,000 feet. This highlights their remarkable dispersal abilities.
  17. Over 121 species of plants have been identified in drift collected during the Challenger expedition. This showcases the role of ocean currents in seed dispersal.
  18. One partridge was found to have carried 82 seeds attached to its foot. This highlights the role of birds in seed dispersal.
  19. Quartz grains have been found in deep-sea ooze over 700 miles from land. This indicates the powerful dispersal abilities of wind.
  20. The smallest seeds in the sample weighed only 1/12,000th of a grain. This showcases the remarkable dispersal abilities of wind in moving even the smallest objects.


  • Species: A group of organisms that can interbreed and produce fertile offspring.
  • Natural selection: The process by which organisms with traits that enhance their survival and reproduction are more likely to pass on those traits to future generations.
  • Variation: The differences that exist between individuals within a species.
  • Hybrid: The offspring resulting from the crossbreeding of two different species.
  • Mongrel: The offspring resulting from the crossbreeding of two different varieties within the same species.
  • Mimicry: The evolution of one species to resemble another species, usually for protection.
  • Warning coloration: Conspicuous coloration that warns predators of an organism’s inedibility or dangerous defenses.
  • Sexual selection: A type of natural selection that acts on traits related to reproduction, such as mating displays, competition between males, and female choice.
  • Rudiment: A vestigial organ that has lost its original function, but is still present in an organism.
  • Germ-plasm: The hereditary material that is passed from one generation to the next.


  1. The domestic dog: Multiple wild species of wolves and jackals were likely domesticated and selectively bred, resulting in the incredible diversity of dog breeds we see today.
  2. The domestic pigeon: All breeds of domestic pigeons are believed to have descended from the common rock pigeon (Columba livia). Selective breeding has resulted in birds with drastically different appearances and behaviors.
  3. The Kea (Nestor notabilis): This New Zealand parrot, initially a honey-eating bird, has recently adapted to a carnivorous diet, preying on sheep. This illustrates the plasticity of animal behavior.
  4. The insects of Madeira: Many insects on the island of Madeira have lost their wings or have reduced wings, likely due to strong winds that blow them out to sea.
  5. The dipper (Cinclus): This bird, closely related to thrushes, has adapted to a life in mountain torrents, developing the ability to “fly” underwater to catch prey.
  6. The bromelia leaves: Various insects, crustaceans, and even frogs have adapted to the unique habitat of bromelia leaves, illustrating how diverse organisms can evolve to occupy new niches.
  7. The tiger: The tiger’s stripes provide camouflage in the long grass, effectively concealing it from prey and predators.
  8. The banded fruit pigeon of Timor: This bird, with its white head and yellow belly, appears conspicuous yet is remarkably well camouflaged among the eucalyptus trees it inhabits.
  9. The stick and leaf insects: These insects exhibit a remarkable level of detailed imitation, blending seamlessly with their surroundings to evade predators.
  10. The Royal Persimmon moth (Bombyx regia): This large caterpillar, with its striking orange-red tubercles, appears fearsome and deters predators.


“Darwinism: An Exposition of the Theory of Natural Selection” provides a compelling and insightful examination of the power and scope of natural selection in shaping the diversity of life. By drawing on a vast array of evidence from natural history, anatomy, embryology, and geology, Wallace presents a powerful case for the theory of evolution through descent with modification. While acknowledging the inherent complexity of the process, he demonstrates how natural selection can account for a wide range of phenomena, from the origins of species to the remarkable adaptations of color and behavior.

However, Wallace ultimately questions the ability of natural selection to fully explain the emergence of complex human faculties, such as the mathematical, musical, and artistic abilities. He suggests that these may be evidence of a spiritual element in human nature, transcending the solely material processes of natural selection.

This book offers a valuable and thought-provoking exploration of the theory of evolution, and its impact on our understanding of both the natural world and our own place within it.

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