Human Evolution: A Journey from Primate to Homo Sapiens
The Origin of Life and Humanity
Evolutionary Hypothesis
The evolutionary hypothesis, inferred from paleontological and anatomical data, suggests that humans haven’t always existed on Earth. Our species represents the culmination of a long evolutionary process.
Theories of Evolution
Anaximander’s Theory
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Lamarck’s Theory
Living beings have an inherent tendency to develop and multiply their organs, resulting in more perfect forms. All plant and animal species descend from more imperfect and less developed ones.
- Function Makes the Organ: Frequent use of an organ leads to its development and enhanced capacity, and vice-versa.
- Transmission of Acquired Characters: Some changes are inherited by offspring, giving rise to new species.
- Adaptation to New Conditions: Species in disadvantaged environments tend to adapt to new conditions. Lamarck’s example is the evolution of giraffes.
A key question is whether humans are part of this evolutionary process.
Darwinism
Darwin, the first to defend the evolution of all species, including humans, published On the Origin of Species and The Descent of Man. These works explain his complete theory of evolution, proposing that all animal and plant species descend from earlier species.
Natural Selection: All species tend to reproduce and multiply, eventually saturating their habitat. This leads to a struggle for survival, where the fittest individuals prevail.
On the Human Species: Darwin posited that humans are a product of the animal kingdom, evolved from a previous animal. Africa is the cradle of humanity. Human characteristics include being spiritual beings (homo faber), possessing a moral sense, and exhibiting a gradation in cultures and races. Darwinism challenged the Christian worldview.
Mutationism
In the mid-19th century, Mendel established that inheritance follows statistical laws. Hugo de Vries theorized about mutations, variations (due to environmental factors), and changes. Variations affect the body but are not transmitted, while mutations in germ cells induce changes that are transmitted, causing changes in the species.
The Synthetic Theory
The discovery of DNA and advances in paleontology and genetics have enhanced our understanding of evolution. Current theories define the world of living beings as a complex of species undergoing slow but steady evolution, involving both natural selection (Darwin) and mutations (de Vries).
- Rejection of the inheritance of acquired characteristics
- Ratification of gradualism in evolution
- Recognition of natural selection and mutation as inheritance mechanisms. Mutations explain random variation, while natural selection directs evolution.
The Process of Hominization
Hominization refers to the evolutionary process that led from primitive hominids to modern humans. The “ecological challenge”—the need to survive in a new environment—drove this process.
Anatomical Features
- Bipedalism: Hominids living in trees had a complete view, but descending to the ground required standing above vegetation to locate food and predators. Bipedalism provided this advantage.
- Release of the Hands: Freed from locomotion, hands became tools for making utensils. The five fingers retained harmonic motion, progressively adapting to perform technical functions.
- Brain Development: Bipedalism and hand use led to central nervous system development and increased brain size and complexity. The vertical position reduced the need for large jaws and facial muscles, allowing for greater cranial capacity.
Physiological Traits
- Eating Habits: Humans adapted their diet, becoming omnivorous. Fire played a vital role in this adaptation.
- Neoteny: A delay in reaching maturity, allowing for longer development and learning, possibly facilitated by fire and cave dwelling.
Psychic Traits
- Social Cooperation: Cooperative activity allowed for better use of food and territory.
- Language: The need to organize increasingly complex tasks led to the development of a broader range of sounds, forming the basis of language.