Life's Origins and Species Evolution

Origin and Evolution of Life

In the 6th century BC, philosophical inquiry began with questions about existence. Three primary perspectives emerged: religious, philosophical, and scientific. Scientifically, the Big Bang theory explains the universe's origin as a massive explosion of matter and energy, leading to a long process of development. Religious explanations are based on myths, such as creationism and intelligent design in Western culture. Philosophically, early thinkers sought the fundamental principle (arkhé) of the cosmos, often focusing on physical elements like water (Thales).

Origins and Evolution of Species

Fixism

In the 4th century BC, Aristotle classified living beings by species and genera, observing that species are eternal and unchanging. This view, tied to creationism, held that species were perfectly designed and did not evolve. Fixism persisted, with further classifications in the 18th century.

Transformism

Lamarck, in the 18th century, challenged fixism, arguing that living beings adapt to their environment, with unused organs atrophying and others developing. However, he incorrectly believed all changes were heritable.

Darwinism

Darwin's 19th-century observations led him to propose that all living things share a common origin, with species changing progressively through natural selection. This theory explains how species adapt to environmental changes, but not how these changes are inherited.

Mutationism

This theory explains how changes occur within a species but not the extent of possibilities. Mendel's laws revealed how genetic information is inherited through dominant and recessive genes. In the 20th century, the structure of DNA was discovered, raising ethical considerations about modification.

Synthetic Theory

This contemporary theory combines Darwinism, Mendelian genetics, and newer theories like saltationism, which suggests occasional abrupt speciation.

Hominization

Hominization is the random evolutionary process that led to Homo sapiens. Key stages include:

• Early Primates: A group of lemurs took refuge, leading to changes in offspring care.
• Mammalian Evolution: Primitive primates developed nocturnal hunting and enhanced visual skills.
• Australopithecus: Emerged around 4 million years ago.
• Homo habilis: Appeared around 2 million years ago, with increased cranial capacity and agricultural beginnings.
• Homo erectus: Around 1.6 million years ago, developed sophisticated hunting and tool use.
• Homo antecessor: Around 800,000 years ago, found at Atapuerca, were carnivorous hunter-gatherers.
• Homo sapiens: Emerged around 250,000 years ago, with increased cranial capacity and symbolic thought.

Anatomical Changes

• Bipedalism:
• Encephalization: Brain size and complexity increased.
• Hand Shortening: Opposable thumbs facilitated tool use and intelligence.

Physiological Changes

• Freed Hands: Enabled tool use and environmental transformation.
• Brain Development:
• Plasticity and Adaptability:
• Reproductive Control:

Social Changes

• Intensified Social Life: Organized hunting and group living.
• Complex Language: Essential for complex social structures.

Humanization

Humanization marks the shift from biological evolution to cultural development. Key factors include:

• Fire Discovery: Provided light, warmth, cooked food, and a social gathering point.
• Tool Production: Enabled specialization of tasks.
• Agriculture: Ensured food supply and led to settled communities.

Thinking and Language

These developments required a complex brain and led to symbolic thought and language, establishing a code for communication within communities.