The History and Mechanisms of Biological Evolution

The Origins of Life and Biological Evolution

About 15 billion years ago, the universe was smaller than an atom and devoid of matter. Life arose soon after Earth formed, about 3.5 billion years ago. Since that time, life began to evolve.

Defining Biological Evolution

Biological evolution is the process of anatomical and physiological changes experienced by populations of living things, which results in the formation of new species.

Human Evolution: A Unique Process

Human evolution is part of the general evolutionary process, but humanity is a unique species within the process of natural evolution.

Foundational Theories of Evolutionary Change

Various theories of evolution attempt to explain this mysterious unfolding of life.

Lamarckism: Acquired Characteristics

Jean-Baptiste Lamarck attempted to explain the diversity of living organisms as a result of gradual changes. His core ideas included:

• He proposed that all living beings have a natural tendency toward the growth of the organism itself and the improvement of their internal organization.
• He believed the action of the environment causes anatomical and physiological changes in organisms.
• A specific need is reacted to with the use or disuse of an organ, which in turn causes its development or disposal.
• Acquired characters are preserved and passed on through generations.

Darwin and Natural Selection

Charles Darwin observed variability in nature. The world is constantly changing, and organisms are transformed over time. He believed that adverse environmental conditions enable evolution:

• Individuals better adapted to their environment are those who survive, and therefore reproduce.

Mendel and the Birth of Genetics

Through his experiments with plants, Gregor Mendel explained the processes of heredity in living things, opening the way for the new science of genetics. Genetics showed that the evolutionary theories of Darwin and Lamarck did not fully account for reality.

Modern Evolutionary Science and Challenges

Successive theories of evolution have corrected and completed initial hypotheses, although none has completely explained the processes that led to the formation of all species. Some theories proposed explanations based on natural selection, while others focused on mutation.

Unresolved Issues in Evolutionary Theory

One of the problems Darwin faced was determining what constituted a species. The concept of a species is rather philosophical, and therefore science struggles to fully define it. A robust theory of evolution must explain how new individuals appear capable of forming a reproductive community.

Furthermore, it has been difficult to scientifically detect a single factor involved in the natural selection of a particular species.