Evolution, Natural Selection, and Human Origins: A Historical Overview

Theories of Species and Evolution

Fixism: Philosophical current in which species are immutable and do not change over time. Its defender was Aristotle.

Creationism: Religious position defended by Christians, which holds that God created each species at the beginning of time. The Bible was interpreted literally.

Spontaneous generation: Section of agencies that supposedly produced living beings from inert substrates, without prior parent organisms.

Evolutionism: Species change and evolve, and descendants acquire characteristics from their progenitors.

Lamarck

Lamarck argued that species are not invariable but evolve from other species through two principles: the use and disuse of organs, causing major development or atrophy, and the inheritance of acquired characteristics.

Darwin

Within each species, production occurs at random, generation after generation, of a large number of individual variations in their traits. Due to limited resources and external causes (climate, predators, etc.), only some descendants can survive. Those with advantageous traits are better adapted to the environment and pass those characteristics on.

Social Darwinism

Social Darwinism is a theory inspired by natural selection that transfers the biological theory of natural selection to social phenomena. In this way, it proposes the survival of the fittest among individuals in different social relations, extending to aspects of increasing complexity in human communities.

Mendel

Mendel formulated three laws, which state that the characteristics transmitted to descendants are inherited independently of one another.

The Synthetic Theory of Evolution

Variability and genetic variation arise from mutations and genetic recombination produced at random. Natural selection acts on these variations, which is among the main mechanisms of evolution.

Punctuated Equilibrium

Evolution involves no abrupt change; instead, it proceeds through gradual but sometimes rapid change.

Endosymbiotic Theory

Through the association of prokaryotic cells, eukaryotic cells were formed, giving rise to all living organisms.

Human Evolution

Hominization refers to the morphological, physiological, psychological, and social changes that allowed the appearance of the human species. Its key evolutionary milestones include:

• Bipedalism: the difference between hominids and other primates, and the increase in brain capacity.
• Cranial capacity: the genus Homo and its appearance.

Homo habilis

Increased cranial capacity compared to Australopithecus, opposable thumb, manipulation of objects, and the manufacture of tools.

Homo ergaster and Homo erectus

Major tools, group living, cooperation to hunt more effectively, carnivorous diet, brain development, and use of fire.

Ancestors of Homo sapiens

From this stage, the species evolved toward Homo sapiens.

Homo neanderthalensis

Tools for hunting, cold-climate adaptations, funerals, awareness of death, and a religious conception.

Homo sapiens

High cranial capacity, anatomy similar to our own, domestication of fire, logical reasoning, and symbolic capacity. Three major advances stand out: the invention of increasingly efficient tools, the development of articulated oral language, and the capacity for symbolic representation and culture.

Nature and Culture

Nature: Individual genetic determinants present from birth, along with the buffering characteristics that define the human being, encoded in the genome.

Culture: Everything that humans learn or acquire, including knowledge, sciences, inventions, customs, and the global accumulation of knowledge and innovations acquired and spread within the social group. The amount of knowledge transmitted to successive generations and individuals depends on the social context.

Transmission of Information

Information is transmitted through oral communication, which carries knowledge from one generation to the next over time. Writing allowed knowledge to be preserved and disseminated with greater rigor and reliability than oral language.

Characteristics of Humans

• Invention: Customs and tools invented by humans.
• Transmission of the past: Imitation of behaviors and actions, enabling communication and passing knowledge across generations.
• Learning: The ability to acquire habits and behaviors not genetically received, allowing inventions to be maintained from past to present and future.