Evolution of Life: From Supernatual to Natural Selection
The Origin and Organization of Life
Living Organisms and Vital Functions
Living organisms perform essential functions: they exchange matter and energy (metabolism) through nutrition, reproduce, and respond to environmental information. They are composed of cells, which are made up of organized molecules. These molecules include organic biomolecules specific to living things and some inorganic biomolecules. These molecules assemble to form organelles and constitute cell structures. Understanding the origin of life requires understanding how biomolecules originated and organized.
Supernatural Origin
The idea of a supernatural creation has no place in science because it belongs to the realm of personal beliefs. Science should neither affirm nor deny such beliefs. Many theories about the origin of life have contained or been based on ideas like vital spirit or life force.
Spontaneous Generation
Spontaneous generation refers to the formation or origin of a living being from non-living matter, the chemical transformation of certain substances under specific environmental conditions.
Lamarck’s Ideas
Lamarck proposed the following:
- Simpler life forms often arise through spontaneous generation.
- All organisms have an instinctive momentum that leads them toward perfection and complexity.
- Environmental changes create new needs in individuals, forcing them to respond by using certain organs more and others less. This leads to the formation, development, impairment, or atrophy of those organs, causing alterations in the organism’s constitution. This is where the concept of “function creates the organ” comes from, explaining how each feature appears in a species to play a certain function.
- Alterations in the development, acquisition, or loss of organs are maintained and transmitted to offspring, preserving and increasing them in subsequent generations, resulting in evolutionary change. This explanation of how one life form can change into another is known as the inheritance of acquired characteristics.
Analysis of Lamarck’s Proposal
Lamarck’s theory suggests that adapting to the environment improves the chances of an organism and its descendants. However:
- There is no proven drive towards complexity in living organisms.
- Current genetic knowledge does not support the inheritance of acquired characteristics. Genes, not traits, are inherited.
Endosymbiotic Theory
Eukaryotic cells originated from smaller prokaryotes that were engulfed by larger ones.
Evolution
The Fact of Evolution
The gradual change in the characteristics of species over time is an observable fact.
Theory of Evolution
The explanation of the origin of all species that populate the planet is a grounded scientific theory.
Fixism and Creationism
Fixism-creationism is the belief that species have always remained identical since their origin, created as they are now. The naturalist Linnaeus, in the 18th century, proposed a natural classification system intended to reflect divine creation. However, his plan to group species according to their similarities revealed kinship relations.
Scientific Theory of Evolution
The scientific theory of evolution proposes hypotheses and experiments or observations to solve the problem of the origin of species. These hypotheses include:
- Species share common components.
- The closer the evolutionary relationship between two species, the greater their similarities; the more distant their origin, the more differentiated their features.
- Some species may have disappeared, but a common ancestor remains, as do others that followed, showing intermediate characteristics.
Darwinian Natural Selection
Darwin’s theory of natural selection states:
- Populations show variations in the characteristics of living individuals, even within the same species.
- These individual differences are mostly heritable.
- They are conditioned by the direct action of the environment (an error in his theory: he accepted the possibility of the inheritance of some acquired characteristics).
- These modifications are known as adaptations.
Conclusions of Natural Selection
True evolutionary change occurs when considering the most suitable for reproduction. Those who survive more, reproduce more, and their descendants inherit the characteristics that enabled their success. Through the continuous accumulation of variations consolidated over generations, varieties or breeds can become new species. Natural selection does not cause changes; it selects among those that appear in each generation.