The Variation of Animals and Plants Under Domestication, Volume II (of 2)

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Gutenberg ID

28897

Title

The Variation of Animals and Plants Under Domestication, Volume II (of 2)

Language

en

Book source

Project Gutenberg

Description max 80 words

In this seminal scientific work, Charles Darwin explores the mechanisms of variation and inheritance in domesticated animals and plants. With a tone of rigorous observation and philosophical inquiry, the text challenges readers to reconsider the origins of species, the power of selection, and the intricate laws governing biological change.

Summary up to 500 words

In Volume II of 'The Variation of Animals and Plants Under Domestication,' Charles Darwin systematically dissects the mechanisms driving the diversity of domesticated species. He argues that the vast array of breeds seen in nature arises not from chance, but from the accumulation of slight, fluctuating variations guided by the paramount power of selection. Darwin meticulously examines inheritance, demonstrating that it follows complex laws rather than randomness. He details how traits ranging from eye peculiarities to inherited diseases and longevity are passed down, while also noting instances of weak or fluctuating inheritance in traits like dwarfness and fruit color. A central theme is the phenomenon of reversion, or atavism, where latent ancestral characters reappear in descendants. Darwin explores how crossing distinct varieties often obliterates differences but can also induce sterility, whereas close interbreeding augments morbid tendencies. He posits that domestic races originate through the divergence of characters and the extinction of intermediate varieties, a process driven by both methodical and unconscious selection by humans. Darwin investigates the causes of variability, attributing them to changed conditions of life, the use and disuse of organs, and correlated variability, where modifications in one body part affect others. He addresses the direct action of external conditions, such as climate and food, on an organism's structure and chemical properties. Furthermore, he discusses the laws of variation, including the effects of mechanical pressure and the correlation between homologous parts. The text culminates in Darwin's provisional hypothesis of pangenesis, proposing that 'gemmules' from every part of the body are transmitted to the reproductive organs, explaining inheritance, reversion, and the effects of crossing. Throughout, Darwin maintains that while the precise cause of every individual difference remains unexplained, the general laws of variation and selection sufficiently account for the adaptation and diversity observed in nature. This work serves as a foundational text for evolutionary theory, illustrating how the plasticity of organization and the struggle for existence lead to the formation of distinct breeds and species.

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Categories

• Science
• Biology