9.b.1. Lamarck's theory of evolution
Lamarck's theory of evolution appeared in his Zoological Philosophical Work written in 1809.
His evolutionary theory was as follows:
- Environmental changes generate new needs
- These needs determine the use or disuse of some organs
- Such organs develop or are diminished
- The acquired characters are hereditary
Therefore, this theory of evolution is also a theory of the human origin.
The famous expression for Lamarck's Theory of evolution is functions create organs and heredity determines the change in offspring. Therefore, human origin is the monkey thinking.
A typical example of Lamarck’s theory is the evolution of the necks of giraffes, due to the effort of eating leaves from the trees.
9.b.2. Theory of evolution of Darwin
This point refers to the biological theory by Charles Darwin, the English Naturalist in his main work The Origin of the species, en 1859.
As a contrast to Lamarck's evolutionary theory, Darwin's theory of evolution proposed natural selection as the basis of evolution and human origin. His theory was as follows:
Individuals display differences
Shortage of food leads them to fight for existence
Individuals with superior differences have more chance to reach adulthood, reproduce and transmit these variations to their offspring
From a philosophical point of view, the Theory of Natural Selection of Darwin base on the emergentism.
Later, in his The Origin of Man and Sexual Selection (1871), he added a new factor of evolution and human origin, sexual selection, in which male or female chooses partners with more attractive qualities.
The scientific community generally accepted the evolutionary theory of Darwin (in opposition to Lamarck's), as presented in his work The Origin of the Species in 1859. This theory of human origin and evolution of Darwin has been updated many times while keeping its essence; it maintains that individuals present/display variations and that evolution is determined by natural selection.
The variations in DNA or in the genes are random mutations in self-adaptations of Darwin theory of evolution, in order to remark its character supposedly not directed.