Evolutionary Theories: Lamarck, Darwin, Neo-Darwinism, and Hominization
Lamarck’s Theory of Evolution
Lamarck proposed an evolutionary theory, albeit incorrect in its explanation of how evolution occurs. He focused on the use and disuse of organs. His main points were:
- Species are not invariable; they evolve from one another.
- The use or disuse of organs causes their development or atrophy.
- These acquired characteristics through use or disuse are inherited, leading to degeneration and eventual disappearance over generations.
Darwin’s Theory of Evolution
Darwin provided the key to understanding how evolution occurs. During his voyage on the HMS Beagle, he discovered that species are not fixed. His hypotheses included:
- Within the same species, there are many variations; no two individuals are alike.
- Humans practice artificial selection to obtain strains with desired characteristics.
- In the Galapagos Islands, different varieties of finches and tortoises existed due to geographically isolated populations evolving independently.
- The fossil record, initially explained by the universal flood theory, was reinterpreted by evolutionists as remnants of vanished species.
Darwin discarded Lamarck’s principles. After reading Malthus, he understood that any species could spread rapidly across the Earth, but a mechanism must exist to eliminate a portion of the individuals born. He called this mechanism natural selection. The evolutionary process, according to Darwin, is as follows:
- Within each species, individuals exhibit small, random variations in their traits.
- Not all offspring can survive; the most suitable ones survive.
- The process is gradual and continuous.
- There is a community of descent.
Neo-Darwinism
Neo-Darwinism was developed with contributions from other sciences to reaffirm the theory of evolution through the construction of phylogenetic trees.
- Paleontology: The study of fossils initially supported the diluvian theory, but this failed to explain the progression of species. It was replaced by the theory of catastrophes, where natural catastrophes since the creation of the world eliminated ancient species, leading to more perfect species each time. Darwin found a more consistent explanation, suggesting that fossils were the remains of vanished species and their evolutionary transformations.
- Comparative Anatomy: This field established relationships between species based on their body structures and functions.
- Embryology: The study of embryo development in living things revealed evolutionary changes between species.
- Genetics: The study of the transmission of biological characteristics provides the most significant evidence today. It demonstrates variability among individuals. The hereditary material transmitted to offspring can be altered randomly, and sexual reproduction recombines the characteristics of the parents.
Hominization
Following the extinction of the dinosaurs, mammals occupied various ecological niches. Tree-living mammals adapted with differentiating features:
- Upright posture
- Hands with grasping ability
- Neck joining the body
- Encephalization (brain size of approximately 1350 cc)
- Nearly vertical face
- Slow maturation
- Sophisticated language for communication and reflection
- Social, cultural, and historical beings
- Lobed pinna (earlobe)
- Existence of labia majora in the vulva
- Vaginal opening in females
- Bare skin