Evolutionary Theories: Lamarck vs. Darwin and Genetic Basis

The Lamarckian Theory of Evolution

Jean-Baptiste Lamarck set out a detailed conception of the theory of evolution and its mechanisms. The Lamarckian theory, which can be synthesized in the expressions: "evolution creates the organ" or "environmental influence," can be summarized as follows:

1. The environment, where living things develop, is subject to change, disrupting life within the system and the needs of the organisms inhabiting that environment.
2. Changes in environmental needs produce changes in behavior, developed to meet new necessities.
3. In turn, behavioral change requires changes in the anatomical or physiological structure of living organisms.

The Darwinian Theory of Evolution

The reason Charles Darwin's name is associated with the idea of evolution, rather than Lamarck or another earlier publicist, is partly due to his highly distinguished contribution to the subject, which was subject to extensive and detailed testing. Darwin, according to J. Huxley, based his theory of evolution on three observable facts and two deductions derived from them.

Darwin's Observations:

1. The first fact Darwin observed was the tendency of all living organisms to increase in proportion to a geometric progression.
2. Despite the trend of gradual increase of individuals of different species, the number of individuals of different species remains approximately constant.
3. The third fact Darwin observed was that variations occur among different individuals of a species; individuals vary so markedly.

Darwin's Deductions:

1. The first deduction Darwin made was the struggle for existence.

Genetic Mutation: A Change in Genes

Genetic mutation is a change in the structure of a gene or gene cluster, which can be manifested in the modification of individual characters or remain as potential future variability. It is known that certain chemical substances and physical agents can cause mutations.

Teleonomy: Purpose in Biological Processes

Teleonomy, a word of Greek origin composed of telos (end or goal) and nomos (law or norm), refers to the rules or laws governing biological processes of living beings that are designed to achieve their purposes, their survival, and reproduction in order to perpetuate the species.

Natural Selection: Adapting to the Environment

Natural selection is a process that, alongside random genetic mutations, selects only those mutations that are adaptive to the environment.

Hominization: The Process of Human Evolution

Hominization is the process of morphological, physiological, psychological, and social changes that, promoted by evolution in the animal world, have allowed the appearance of the human species. This process is considered to have begun with two major evolutionary innovations: upright posture and encephalization (increased cranial capacity).

Upright Posture: This became the distinguishing factor of hominids over other species.

Encephalization or Increased Cranial Capacity: This was the key determinant of the appearance of the genus Homo.