Understanding the Evolution of Life Forms and Humans
Evolution of Life Forms: A Theory
Conventional religious literature presents the theory of special creation, which suggests that:
- All living organisms we see today were created as such.
- The diversity of life has remained constant since creation and will continue to be the same in the future.
- The Earth is approximately 4,000 years old.
These ideas faced strong challenges during the nineteenth century. Based on observations made during a sea voyage around the world in a sail ship called H.M.S. Beagle, Charles Darwin concluded that existing living forms share similarities to varying degrees, not only among themselves but also with life forms that existed millions of years ago. Many such life forms no longer exist. Extinctions of different life forms have occurred over time, just as new forms of life arose during different periods of Earth’s history. This indicates a gradual evolution of life forms. Any population exhibits inherent variation in characteristics. Those characteristics that enable some individuals to survive better under natural conditions (climate, food, physical factors, etc.) are favored.
Biological Evolution
Evolution by natural selection, in a true sense, likely began when cellular forms of life with differences in metabolic capability originated on Earth.
Mechanism of Evolution
What is the origin of this variation, and how does speciation occur? Although Mendel discussed inheritable ‘factors’ influencing phenotype, Darwin either ignored these observations or remained silent. In the first decade of the twentieth century, Hugo de Vries, based on his work with evening primrose, introduced the concept of mutations—large differences arising suddenly within a population. He believed that mutations, rather than the minor heritable variations Darwin described, cause evolution. Mutations are random and directionless, whereas Darwinian variations are small and directional. Darwin viewed evolution as gradual, while de Vries believed that mutations caused speciation, a process he termed saltation.
Hardy-Weinberg Principle
Within a given population, one can determine the frequency of occurrence of alleles of a gene or a locus. This frequency is expected to remain fixed and constant across generations. The Hardy-Weinberg principle, expressed through algebraic equations, states that allele frequencies in a population are stable and remain constant from generation to generation. The gene pool (the total genes and their alleles in a population) remains constant, a state known as genetic equilibrium.
A Brief Account of Evolution
Approximately 2,000 million years ago (mya), the first cellular forms of life appeared on Earth. The mechanism by which non-cellular aggregates of giant macromolecules evolved into cells with membranous envelopes remains unknown. Some of these cells possessed the ability to release O2. This reaction may have resembled the light reaction in photosynthesis, where water is split using solar energy captured and channeled by appropriate light-harvesting pigments.
Origin and Evolution of Man
Around 15 mya, primates known as Dryopithecus and Ramapithecus existed. They were hairy and walked like gorillas and chimpanzees. Ramapithecus was more human-like, while Dryopithecus was more ape-like. Fossils of human-like bones discovered in Ethiopia and Tanzania reveal hominid features, leading to the belief that around 3-4 mya, human-like primates walked in eastern Africa.