Oparin, Lamarck, and Darwin: Theories of Life’s Origins
Oparin’s Hypothesis on the Origin of Life
In 1922, the Russian biochemist Alexander Oparin published The Origin of Life, detailing his theory:
- The early Earth’s atmosphere was composed of hydrogen, methane, ammonia, and water vapor, without oxygen.
- Ultraviolet rays, electric shocks, and high temperatures caused these gases to react, resulting in many small organic molecules (prebiotic synthesis).
- As the Earth’s temperature lowered, these molecules fell and accumulated, forming a “primordial soup.”
- Molecules reacted further, forming macromolecules and then molecular aggregates (coacervates).
- These aggregates could evolve into cellular structures, the fundamental component of all living things.
Lamarckism: Early Evolutionary Theory
Lamarck proposed that all living organisms are a product of nature, resulting from gradual succession.
His evolutionary theory is presented in four laws:
- Life tends to increase the volume and dimensions of living organisms.
- The production of a new organ results from a new need.
- Organ development and strength are connected to its use.
- Acquired traits are transmitted to descendants.
Lamarck’s ideas can be summarized as:
- Need creates the organ.
- Use strengthens an organ; disuse causes it to degenerate.
- Inheritance of acquired characteristics.
The lasting impact of Lamarck’s thought is the concept of evolution.
Darwinism and Natural Selection
Charles Darwin, a naturalist, gained most of his experience on a five-year voyage aboard the Beagle. His biogeographic analysis, especially of the Galapagos Islands, showed that each island had unique species within each group (e.g., giant tortoises).
This suggested a common origin for species within an archipelago, with differentiation due to geographic isolation. Darwin recognized great variability within species, supporting the evolutionary thesis. He also noted that species have high reproductive capacity, with more individuals born than can survive.
This leads to competition and natural selection, favoring individuals best adapted to prevailing conditions. These individuals produce more offspring, leading to a gradual increase in the favored characteristics. Natural selection is a process of differential reproduction.
Darwin’s theories were published in The Origin of Species (1859). Alfred Wallace independently reached similar conclusions.