Theories of Species Change: From Fixity to Hominization

The Fixity of Species

The concept of the fixity of species posits that species, as created by God, are immutable and isolated groups. This view was notably supported by Linnaeus.

From a philosophical perspective, this idea relates to the immutability of things (as discussed by Plato). Key tenets include:

• Every individual has a predetermined place in nature.
• There is an immutable core to human nature.
• The human being is considered the protagonist of creation.

Foundations of Evolutionary Theory

Evolutionary thought began with the Lamarckian transformist theory. However, the complete evolutionary framework was developed by Charles Darwin, who provided extensive evidence supporting his ideas:

Key Concepts of Darwinian Evolution

• Common Origin of Species
• The Struggle for Survival
• Natural Selection Theory
• Definition of the Fittest (those with more favorable genetic mutations for adaptation)
• Inheritance of traits
• Nature acts randomly and blindly.

Later contributions from geneticists like Mendel, Weismann, Morgan, and De Vries provided evidence for the genetic basis of inherited traits. Evolutionary theory is characterized as:

1. Materialistic
2. Dynamic
3. Progressive

Natural Evolution: The Hominization Process

Hominization is the evolutionary process involving biological changes that led to the emergence of modern humans. Key biological transformations include:

• The initial change was bipedalism (walking on two feet).
• Modification in the structure of the foot.
• Spine modification required for maintaining an upright posture.
• Liberation of the hands, allowing for the creation and management of tools.
• The mouth is no longer primarily needed for attack, leading to changes in the skull structure.
• Increase in skull size, correlating with increased cranial capacity.

Rational human intelligence is believed to have originated from a genetic mutation that occurred in certain individuals, providing them with a significant adaptive advantage.

Cultural Evolution: Humanization and Psychosocial Change

Humanization is the process of psychosocial change. Unlike non-human primates, whose behavior was constrained by fixed, instinctive patterns, early humans developed the ability to learn new techniques and new ways of existence.

Five characteristics significantly favored this cultural evolution:

1. HUNTING: Fostered intellectual development, social cooperation, technical progress, and the development of language.
2. DISCOVERY OF FIRE: Provided security and protection, and enabled a crucial change in diet (cooking food).
3. LONG LEARNING PERIOD: Characterized by slow physical development, lasting up to 16 years (adolescence). This extended period allows the human being the capacity to learn and explore widely.
4. APPEARANCE OF SOCIAL BEHAVIOR: Established patterns of cooperation, diversification of activities, and the emergence of different social roles.
5. EMERGENCE OF LANGUAGE: Crucial for complex communication and cultural transmission.

Stages of Human Species Evolution

The human species emerged in Africa approximately 2.5 million years ago, evolving from earlier hominids. The main species stages include:

• Homo habilis
• Homo erectus
• Homo sapiens neanderthalensis
• Homo sapiens sapiens