Principles of Genetics and Breeding

1.1.3 History of genetics

• In ancient times, people understood some basic rules of heredity and used this knowledge to breed domestic animals and crops.
• By about 5000 B.C. people in different parts of the world had begun applying selective breeding techniques to grow new plant varieties, including types of wheat, maize, rice, and date palms, that had never existed in the wild.
• Ancient people understood that the rules of inheritance also applied to humans. The ancient Greeks were particularly interested in human heredity and evolution. Greek scientists and philosophers hotly debated whether a male or female parent contributed more to an offspring.
• In the 4th century B.C. Aristotle speculated that acquired characteristics, such as a scar that was incurred during life, could be passed on to offspring. He also believed in a widely held theory known as pangenesis.
• According to this theory the particles in the body, called gemmules, reside in the limbs and organs. The gemmules become imprinted with any changes acquired by the body, such as muscle development from exercise. The gemmules then move to the reproductive cells and transfer information about the body’s alterations to these cells. The reproductive cells transmit the acquired traits to offspring through particles called pangenes.
• The theories about the inheritance of acquired characteristics and pangenesis persisted until the middle of the 19th century.
• French zoologist Jean-Baptiste Lamarck formalized the theory of acquired characteristics in his treatise Philosophie Zoologique (1809). Lamarck proposed that organisms evolve by responding to changes in their environment. When organisms undergo a change in order to adjust to their environment, that change acts as a trait that can be passed on to offspring.
• Charles Darwin, supporter of pangenesis believed that the theory accounted for the process of heredity. Related species adapt to their local environments.
• Darwin and Alfred Wallace independently formulated the theory of natural selection, which holds that members of a given species born with more favourable characteristics to deal with their environment would be most likely to survive to pass on these traits to the next generation. This important theory was popularized by Darwin’s publication On the Origin of Species (1859).