Biochemical Origin of Life - Fifth step: Origin of Autocatalytic Systems, Genes, Viruses and Primordial Life

• This step explains how the first self-replicating and hereditary systems appeared in the primitive oceans.
• It marks the transition from simple chemical evolution to truly life-like systems.

• In the primitive oceans, complex nucleoproteins (nucleic acid + protein) were formed.
• Some of these nucleoproteins showed autocatalytic behaviour, meaning they helped to produce more of themselves.
• This is considered the first sign of self-duplication and hereditary behaviour in early evolution.

• Short nucleotide chains (small pieces of nucleic acid) appeared in these systems.
• These acted like primitive genes, capable of storing and passing simple hereditary information.

• Primitive gene-like chains aggregated into larger protroviruses (virus-like nucleoprotein structures).
• These were similar in organisation to present-day viruses but represented early, simple primordial organisms or life-like systems.

• Time of origin: Life is believed to have originated in the oceans about 3.7 billion years ago during the Precambrian period.
• Habitat: Primitive oceans provided the medium for nucleoproteins and early life-like structures.

Characteristics of Earliest Life Forms

1. Heterotrophic: Depended on pre-existing organic compounds in the ocean; could not prepare their own food.
2. Anaerobic: Lived without free oxygen because the early atmosphere lacked molecular oxygen.
3. Virus-like / nucleoprotein nature: Very simple, non-cellular or pre-cellular nucleoprotein systems.

• Nucleoproteins formed in primitive oceans became autocatalytic, i.e., self-duplicating systems.
• These systems showed the first hereditary role of nucleic acids.
• Short nucleotide chains evolved as primitive genes, storing and transmitting information.
• Primitive genes aggregated into protroviruses, similar to simple virus-like structures.
• Life originated in the Precambrian oceans around 3.7 billion years ago.
• Earliest organisms were heterotrophic and anaerobic, relying on existing organic molecules and living without free oxygen.