Evolutionary Theories: Darwinism, Neo-Darwinism, and Hominid Origins

Changes achieved through the development, acquisition, or loss of organs are maintained and transmitted to offspring, which preserves and increases these traits through successive generations. This concept is known as the inheritance of acquired characteristics. However, analysis of these proposals has not demonstrated any inherent tendency or impulse towards complexity in living things. In light of developments in genetics, the inheritance of acquired characteristics is not supported.

Natural Selection: Darwin and Wallace

Darwinian theory posits that in a changing world, organisms also change over time. Some features disappear, and new ones emerge. This process of change is gradual and continuous. Organisms with similarities are related and descend from a common ancestor. The mechanism driving these developmental changes is natural selection.

According to Darwin, living populations show single-variety traits, and these individual differences are heritable. In many cases, there are two types of heritable differences:

• Those determined by the direct action of the environment.
• Spontaneous changes, such as the appearance of individuals with shorter legs in an animal population. These changes allow organisms to adapt to environmental changes, resulting in adaptations.

Despite the potential for population growth, their numbers remain relatively constant through generations. Darwin conceived the idea of the struggle for existence, where only the fittest survive. Evolutionary change occurs through the continuing accumulation of variations consolidated throughout generations, producing new strains or races that could become new species. Natural selection does not determine or cause variations.

Neo-Darwinism: The Synthetic Theory

The synthetic theory, or neo-Darwinism, is a revision of the classical theory of natural selection. It is synthetic because it integrates knowledge about the evolutionary process from Darwinian theory with insights from population genetics. Variations are due to random mutations in individuals within a population. Natural selection favors mutations that are beneficial in a given environment, increasing their frequency and leading to adaptation. Bio-evolutionary change is gradual and slow, driven by natural selection over generations within a population. Through this process, speciation occurs as cumulative differences cause a new population to diverge into a new species. The fossil record provides evidence of the evolutionary process.

From Primate to Hominid

Hominids are a group of non-arboreal primates whose origins are in Africa, dating back at least 7 million years. Homo features include moving in a vertical, bipedal position, a U-shaped palate, and a skull housing a bulky brain. This increased brain volume is related to a diet of high-energy foods.