The History of Evolutionary Biology and Origin of Life Theories

Theory of Spontaneous Generation

For many years, it was believed that living beings were born spontaneously from the decomposition of organic matter. The first scientist who seriously questioned this theory was the Italian Francesco Redi (1626-1697). Redi wanted to show that fly larvae appearing in rotting meat came from flies and not from the flesh itself. In the nineteenth century, Louis Pasteur demonstrated that the widespread belief in spontaneous generation was unfounded. Pasteur concluded that all living beings originate from other living beings.

Formation of the First Cells

In 1922, the Russian biochemist Oparin proposed a theory about the origin of life: the first molecules were formed from the gases of the primitive atmosphere by the action of electrical discharges caused by storms and ultraviolet light from the sun.

Biological Evolution

Evolution is defined as the gradual and progressive transformation of primitive life forms into other, more differentiated and complex organisms.

Fixism and Catastrophism

Fixism

The fixist theory considered that all species were unchangeable and created at the beginning of time. Fossils were viewed as whims of nature (such as shell-shaped stones) or species that disappeared due to disasters, without any evolutionary relationship.

Catastrophism

This theory attempted to reconcile fixism with the existence of fossils. According to this view, the Earth was populated by a succession of flora and fauna independent of each other.

Lamarck's Theory of Evolution

In the 18th century, the French naturalist Lamarck was the first to develop a theory of evolution explaining specific mechanisms:

• Innate tendency for improvement: Living things have an innate drive to improve, allowing them to adapt to different environments.
• Law of use and disuse: Changes in the environment create new needs. Adapting to these conditions causes an increase or decrease in the use of certain organs, leading to physical changes.
• Function creates the organ: When environmental changes originate entirely new needs, entirely new organs may arise in response.
• Inheritance of acquired characters: Because these characters develop and are perpetuated across generations, they are considered hereditary.