Human Evolution and Biological Theories: From Stone Age to Darwin

The Paleolithic and Neolithic Eras

Paleolithic: The oldest Stone Age, spanning from the appearance of humans on Earth until the beginning of agriculture.

Neolithic: The stage where humanity transitioned from nomadism to a sedentary lifestyle, bringing many significant changes.

Key Historical Concepts

• Stone Age Tools: Use of stone and metal (iron, copper).
• Lifestyle Shifts: Transition from nomadism to sedentary living.
• Technological Advancements: Human-pulled plows, animal-pulled plows, and early navigation (rafts and sails).
• Chronology: Paleolithic, Neolithic, Copper Age, Bronze Age, and Iron Age.

Biological Theories of Evolution

Fixism vs. Transformism

Fixism: Maintained that species were immutable, independent, and static, meaning they had not changed their characteristics since they first appeared on the planet. This idea persisted until the mid-19th century.

Transformism: Argued that species change over time, giving rise to different organisms.

Origins of Evolutionary Thought

The first explanations of how species evolved emerged in Ancient Greece. Philosophers and mathematicians such as Thales of Miletus, Aristotle, Anaximander, Empedocles, and Epicurus sought naturalistic explanations for the diversity of living organisms and their adaptation to various environments.

Lamarck's Theory

Proposed in 1809, Lamarck's theory described evolution as a process moving from simple organisms to more complex plants and animals, reaching a peak of perfection in humans. His theory is based on four principles:

1. Existence of an inner drive toward differentiation in all living things.
2. The ability of organisms to adapt to environmental changes.
3. The principle of use and disuse of organs.
4. The inheritance of acquired characteristics.

Darwin's Theory

Charles Darwin's interest in the diversification and origin of species was influenced by the ideas of his grandfather, Erasmus Darwin, and the scientific theories of Lamarck. Initially, at age 18, Darwin did not doubt the immutability of species.

Synthetic Theory of Evolution

Also known as Neo-Darwinism, this theory was developed by a group of biologists in the mid-20th century. It combines Darwinian natural selection with Mendelian genetics. Evolution occurs through the selection of organisms whose traits respond best to the environment, allowing them to reproduce in greater numbers and in less time.