Evolutionary Theories: Lamarck, Darwin, and Modern Synthesis

Evolutionism

According to biology, fixism maintained that the existing living species were independent and immutable and that they had always existed with the same basic characteristics.

From the works of Lamarck and Darwin, evolutionism emerged. It holds that the universe and life in all its manifestations, and therefore all species, are the result of change and adaptation. This theory is called evolution and argues that species living today come from others who have disappeared, and these in turn from another, until reaching the first living organisms. For evolution, all living creatures belong to a single large family that has developed over Earth's history.

Early Evolutionary Theories

Scientists disagree on:

• The mechanisms causing species diversification.
• The evolutionary paths of species over time.
• Whether evolution has a purpose.

Lamarck

According to Lamarck:

• Variations acquired are transmitted to offspring and may create new species.
• Evolution is rationally and scientifically explained by changes in organisms due to environmental influence, resulting from the use or disuse of organs. Used organs develop, while unused ones atrophy.

Lamarck never explained the reason for this trend towards perfection.

Darwin

According to Darwin, the cause of evolution is natural selection.

Populations increase faster than food supply, leading to a struggle for existence between individuals and species. In this struggle, only the fittest survive and reproduce. Advantageous variations are inherited, while weaker individuals are eliminated. The best-adapted survive and pass changes to their descendants.

Darwin believed evolution has no purpose. Changes in organisms are due to chance, depending on environmental circumstances.

Lamarck and Darwin

They posed a problem: why are some changes inherited and others not?

There was a scientific inability to distinguish between changes caused by environmental factors (not inherited) and mutations in genes (inherited). Mendel's discoveries about heredity and Hugo de Vries's work on genes helped clarify this.

Modern Evolutionary Synthesis

Synthetic theory of evolution or neo-Darwinism.

Its basic tenets are:

a) Organisms experience random mutations.

b) Mutations are relatively common in all species.

c) Some mutations are favorable, others unfavorable. Natural selection favors those with genes better adapted to the environment.

d) Beneficial mutations are inherited, leading to better adaptation.

In short, random mutations causing variations are inherited, and natural selection directs evolution by eliminating non-adaptive varieties and perpetuating the best-adapted individuals.

Hominization Process

This is the process of humanization, the emergence of humans from other primates.

The oldest hominid fossil set is Ardipithecus.

Understanding Evolution

Evolution has no purpose or direction towards perfection. In common language, "evolution" means "change for the better," but in Darwinism and neo-Darwinism, it simply means "change."

Evolution and Religion

Religious stories often depict God creating man directly. However, creation accounts do not necessarily contradict evolution or the idea that humans evolved from other life forms. They provide religious meaning to human existence. Both fixity and evolution are scientific theories compatible with creationism.