The Pre-LUCA Evolution Timeline
Deep orange or reddish-brown atmosphere: The second atmosphere’s formation was crucial and occurred just before or alongside the formation of Earth’s oceans, which directly supported the evolution of organic molecules and prebiotic microenvironments. The second atmosphere began to develop around 4.5 to 4 billion years ago, as volcanic outgassing released gases trapped in the Earth’s […]
Second Atmosphere: Carbon Dioxide & Nitrogen Read More »
Likely white or grayish atmosphere: The first atmosphere developed first but was not directly involved in the development of life. The first atmosphere formed shortly after Earth’s formation around 4.5 billion years ago. This initial atmosphere was primarily composed of hydrogen and helium, the lightest and most abundant elements in the universe, which were captured from
First Atmosphere: Hydrogen & Helium Read More »
As the Earth cooled following its formation, outgassing from volcanic activity released water vapor and other gases into the atmosphere. When the Earth’s surface cooled sufficiently, this water vapor condensed and fell as rain, filling the basins that would become oceans.
First Oceans: Fresh Water Read More »
The synthesis of simple organic molecules such as formaldehyde (H₂CO), methanol (CH₃OH), and simple hydrocarbons in the dense molecular clouds of the interstellar medium occured once sufficient carbon was present. This process has been ongoing for billions of years but became more prevalent as the universe aged and more carbon became available. Big History Thresholds:
Interstellar Clouds: Organic Molecules Read More »
The chemical evolution from inorganic precursors to organic molecules is a fascinating story of transformation driven by Earth’s dynamic early conditions and possibly assisted by the input from space in the form of meteorites rich in organic compounds. During this period, the Earth witnessed a series of complex chemical reactions facilitated by its primordial atmosphere,
Inorganic Precursors to Organic Molecules Read More »
About 3.85 billion years ago, the RNA world resembled a molecular wild west: replicators drifted. When chemistry favored a structure, it binded.
About 3.9 million years ago RNA-based protocells evolved. Likely with a mix of random DNA experiments.
Assembly of Protocells Read More »
Alongside or following the chemical evolution of organic molecules, the formation of prebiotic microenvironments, such as hydrothermal vents or warm little ponds, provided niches where concentrations of organic molecules could interact. These environments could have been crucial for the assembly of complex organic molecules and the initiation of catalytic cycles.
Formation of Prebiotic Microenvironments Read More »
While the 4.4 billion years ago is a guess as to when these processes might have started, the 4.1 billion years ago guess is a better representatoin of current understanding on when the needed building blocks of life evolved. Before the appearance of self-replicating molecules, there was a crucial phase of chemical evolution where simple
Chemical Evolution of Organic Molecules Read More »
About 4.2 billion years ago, chemical reactions in high temperature environments start replicating. Not life, just replication.
First Life: Self-Replicating Molecules Read More »
The formation of cellular membranes represents a pivotal development in the pre-life world, enabling the creation of defined boundaries for primitive cells. These membranes, likely formed from simple lipid bilayers, provided a controlled environment for chemical reactions and played a critical role in the emergence of the first cell-like structures, distinguishing them from their surrounding
Cellular Membranes Read More »
Metabolism-First life theories suggest life began as a series of self-sustaining chemical reactions trapped in rock pores about 4.1 billion years ago.
Metabolic Pathways Read More »
The Earth and the other planets formed 4.5 billion years ago from the same cosmic cloud—the primordial material which gave birth to the Sun. The dust and comets—the rocks—were composed largely of hydrogen, ice, carbon, and nitrogen.
4.6 billion years ago, a cloud of gas and dust collapsed under the force of its own gravity to form our solar system.With the Sun at its center, glowing, the planets had not yet formed. The Sun, a G-type Population 1 star, shines brightly with a surface temperature of about 9,400 degrees, 5,500 Kelvin, and
Legacy: Began enriching the interstellar medium with heavier elements, including carbon, necessary for organic chemistry From the ashes of Population III stars, celestial giants, rose a new generation of stars, the Population II stars. These stars contained a higher proportion of the heavier elements, granting them a longer lifespan, and likely the company of planets.
Population II Stars: Heavy Element Synthesis Read More »
Legacy: First 26 elements of the periodic table of elements. After a few hundred million years, gravity continued to play its part, drawing atoms into an intimate collapse, giving birth to the very first stars and galaxies. These first stars, known as Population III stars, were stellar giants: massive, hot, and short-lived; they burned for
Population III Stars: Heavier Elements Read More »
About 3.75 billion years lived LUCA. Not first life, but the common ancestor of all life today. LUCA used DNA, had ribosomes, used ATP, and had translation machinery. It lived in high-temperature environments.
LUCA: Last Universal Common Ancestor Read More »
