The Dawn of Reason; Or, Mental Traits in the Lower Animals Informative Summary


This book delves into the surprising mental capabilities of animals, arguing that many creatures possess a wider range of cognitive abilities than previously thought. Dr. Weir, a biologist and physician, challenges the traditional view that animal behavior is driven solely by instinct. He presents evidence of conscious determination, memory, emotions, reason, and even aestheticism in a variety of species, from insects to mammals.

The book meticulously examines various senses in animals, exploring their development and function in different creatures. It then moves on to explore the complex interplay of these senses with conscious determination, memory, and emotions. Dr. Weir meticulously documents observations of animals engaging in seemingly thoughtful actions, such as the mud-dauber wasp learning to avoid a window after a single experience, or the ant displaying care and sympathy for injured companions. He also explores the intriguing realm of animal aestheticism, showcasing examples of animals who appreciate music, enjoy personal cleanliness, and even engage in decorative arts.

Key Findings:

  • Animals are capable of conscious determination. Dr. Weir argues that even the simplest organisms, like the protozoan Stentor polymorphus, display signs of choice and decision-making. He provides numerous examples of animals, such as the water-louse and the garden snail, exhibiting conscious effort and purposeful behavior.
  • Animals possess a wide range of cognitive abilities. The book presents evidence of memory, emotions, reason, and even abstract ideas in various species. This challenges the traditional view that animals are simply driven by instinct.
  • Animals possess auxiliary senses beyond those found in humans. Dr. Weir explores two senses specific to certain animal species: tinctumutation (color-changing) and the “homing sense” (sense of direction). He presents fascinating evidence and experiments to support his findings, highlighting their evolutionary significance.
  • Instinct and reason are not mutually exclusive. The book emphasizes that while instinct plays a crucial role in animal behavior, it does not preclude the existence of reason. Dr. Weir provides examples of animals exhibiting intelligent adaptations to unforeseen situations, demonstrating their ability to reason and make complex decisions.


  • The evolution of mind: By studying animals, we can gain valuable insights into the evolution of mind, observing how simpler forms of cognition develop into more complex capabilities. This helps us understand the origins of our own mental abilities.
  • The interdependence of morphology, physiology, and psychology: Dr. Weir highlights the interconnectedness of these three aspects of life, demonstrating how physical adaptations and physiological functions impact and shape animal behavior and cognition.
  • Animal communication: The book presents evidence suggesting that animals can communicate complex ideas and emotions, challenging the long-held view of animals as non-verbal creatures.
  • The importance of careful observation: Dr. Weir emphasizes the need for meticulous observation and experimentation to understand animal behavior. He encourages readers to look beyond simple assumptions and seek evidence of complex cognitive abilities in even the smallest creatures.
  • The ethical implications of our understanding of animal cognition: By recognizing the mental capabilities of animals, we gain a new perspective on our relationship with the natural world, raising questions about our responsibilities towards other species and challenging our anthropocentric biases.

Historical Context:

The text was written in 1899, a time of significant scientific advancements in natural history and evolutionary theory. Darwin’s theories on evolution and natural selection were gaining widespread acceptance, prompting new investigations into animal behavior and cognition. This book reflects the emerging debate about the nature of animal intelligence and the growing recognition of the mental capabilities of creatures beyond humans.


  • The sense of touch is likely the most primal sense. It is likely present even in the simplest organisms.
  • Actinophryans possess taste. They can distinguish between starch spores and sand grains.
  • Animals adapt their structures to new environments. This is evident in the evolution of flat fish, whose eyes have migrated to the top of their heads to adapt to a bottom-dwelling lifestyle.
  • Total darkness can lead to degeneration of sight organs. This is illustrated by the mole, which has rudimentary eyes and can only differentiate between light and darkness.
  • Light can be fatal to some animals. Blind cave fish are highly sensitive to light and die quickly when exposed to it.
  • Primitive eyes (ocelli) appear in animals very low on the evolutionary scale. The jelly-fish possesses these primitive eyes around the margin of its bell.
  • The crayfish has compound eyes, providing a mosaic-like picture of its surroundings.
  • The Periophthalmus fish can leave the sea and live on land, using its pectoral fins as legs. This adaptation allows it to hunt for its prey, the Onchidium mollusk, which possesses unique dorsal eyes.
  • The pineal gland in humans is a remnant of a third eye.
  • Sound vibrations are converted into nerve energy through the auditory organs.
  • The antennæ of insects are not always the seat of auditory organs.
  • Grasshoppers and crickets have ears located in their front legs.
  • The balancers of flies are auditory organs.
  • Butterflies have ears in their antennæ.
  • The maxillary palpi of beetles are crucial for hearing.
  • Nerve-tissue is present in all animals above Hydrozoa.
  • The nervous system of Stentor polymorphus is well-developed.
  • Conscious determination arises from reflex action.
  • Nerve-tissue possesses memory.
  • The association of ideas (stimuli and reflexes) is a key feature of nerve function.


  • The jelly-fish can have as many as 600 “eyes” (marginal bodies).
  • The sea-urchin’s lens looks like a “brilliant egg in a scarlet nest.”
  • A garden snail can see a moving white object at a distance of two feet.
  • A crayfish can see a man at a distance of 20-25 feet.
  • The “red-legged locust” (Melanoplus femur-rubrum) has a series of graduated auditory vesicles in its balancers.
  • There are six rows of graduated auditory vesicles in the balancers of the horsefly (Tabanus atratus).
  • The queen of a termite colony can lay over 80,000 eggs in 24 hours, or one egg every second.
  • A queen termite can live for about two years, laying approximately 60 million eggs.
  • The abdomen of a queen termite can grow to be 2,000 times the size of the rest of its body.
  • The honey-making ant (Myrmecocystus mexicanus) stores honey in the bodies of specialized ants.
  • Harvester ants in Arkansas have no pathways or roads leading to their nests.
  • The mason wasp deposits five spiders in cells for male larvae and eight spiders in cells for female larvae.
  • A blind collie dog could count her six puppies and recognize when one was missing.
  • A mule once stopped working after completing its 50th trip, regardless of the time of day.


  • Monera: One-celled organisms, lacking differentiated nerve cells.
  • Nervoid: Relating to or resembling nerve tissue.
  • Chromatophore: A pigment-containing cell, responsible for color changes in animal skin.
  • Tinctumutation: The ability to change color based on surrounding environment.
  • Letisimulation: The act of feigning death to avoid predators.
  • Cuniculi: Tunnels or burrows, particularly those created by mites in the skin.
  • Ptomaines: Poisonous substances produced by the decomposition of animal matter.
  • Mutualists: Organisms that live in a mutually beneficial relationship, often involving one species providing a service in exchange for food or protection.
  • Ganglion: A cluster of nerve cells, acting as a nerve center.
  • Ocelli: Simple eyes, found in some invertebrates, capable of detecting light.


  • The actinophrys’s selection of starch grains over uric acid crystals. This demonstrates the ability of these simple organisms to recognize food by taste.
  • The flounder’s evolution of unilateral eyes. This adaptation illustrates how animals adjust to new environments.
  • The mole’s inability to see but its ability to differentiate between light and darkness. This exemplifies the degeneration of sight organs in animals living in perpetual darkness.
  • The jelly-fish’s response to light. This shows how even simple creatures can exhibit purposeful behavior, driven by a sense of light.
  • The bombardier bug’s use of a foul-smelling secretion for defense. This demonstrates how animals can utilize specialized physical features for protection.
  • The mud-dauber wasp’s learning from a single experience. This highlights the capacity for learning and adaptation in insects.
  • The ant’s ability to recognize and care for its injured companions. This illustrates the complexity of social behavior and the presence of empathy in insects.
  • The honey-making ant’s adaptation to a new environment. This shows how ants can exhibit intelligent problem-solving and adapt to challenging situations.
  • The termite colony’s division of labor. This demonstrates the intricate social structure and communication within insect communities.
  • The harvester ant’s agricultural practices. This reveals the remarkable intelligence and complex behavior of ants in maintaining and managing their food sources.
  • The mason wasp’s ability to count spiders and differentiate between male and female eggs. This showcases the remarkable cognitive abilities of insects, including the ability to compute.
  • The blind collie dog’s ability to count her puppies. This suggests that even animals lacking certain senses can develop sophisticated cognitive abilities.
  • The elephant’s ability to recognize and handle objects based on their properties. This exemplifies the ability of elephants to form abstract ideas.


This book provides a compelling argument for the existence of a wide range of cognitive abilities in the animal kingdom. Dr. Weir’s meticulous observations and experiments challenge traditional views about animal intelligence, demonstrating that many species possess conscious determination, memory, emotions, reason, and even aestheticism. The book’s central message is that while instinct plays a crucial role in animal behavior, it does not preclude the existence of intelligence, reasoning, and even abstraction in many creatures. This understanding compels us to reconsider our relationship with the animal world and embrace a more holistic perspective on the evolution of mind.

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