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Origin of Life
a year ago
General
The origin of life on Earth is a complex process that likely involved several stages, including:
Chemical evolution
Stars created atomic elements that could form simple molecules in space. These molecules could have rained down into Earth's oceans.
Replicating molecules
These molecules evolved and began to copy themselves, passing their genetic information on to offspring.
Cell membranes
Replicating molecules became enclosed within a cell membrane, which allowed the internal environment to differ from the external environment.
Metabolic processes
Some cells evolved more modern metabolic processes, outcompeting those with older forms.
Multicellularity
Multicellularity evolved.
Protective membranes
Life developed a protective membrane that wasn't soluble in water. Lipids, fatty molecules, may have been essential for this step.
The earliest evidence of life on Earth includes:
Biogenic graphite in 3.7 billion-year-old rocks from Western Greenland
Microbial mat fossils in 3.48 billion-year-old sandstone from Western Australia
"Remains of biotic life" in 4.1 billion-year-old rocks in Western Australia
Putative microfossils in 4.28 billion-year-old hydrothermal vent precipitates in Quebec, Canada
The transition from non-living to living entities has never been observed experimentally.
Chemical evolution
Stars created atomic elements that could form simple molecules in space. These molecules could have rained down into Earth's oceans.
Replicating molecules
These molecules evolved and began to copy themselves, passing their genetic information on to offspring.
Cell membranes
Replicating molecules became enclosed within a cell membrane, which allowed the internal environment to differ from the external environment.
Metabolic processes
Some cells evolved more modern metabolic processes, outcompeting those with older forms.
Multicellularity
Multicellularity evolved.
Protective membranes
Life developed a protective membrane that wasn't soluble in water. Lipids, fatty molecules, may have been essential for this step.
The earliest evidence of life on Earth includes:
Biogenic graphite in 3.7 billion-year-old rocks from Western Greenland
Microbial mat fossils in 3.48 billion-year-old sandstone from Western Australia
"Remains of biotic life" in 4.1 billion-year-old rocks in Western Australia
Putative microfossils in 4.28 billion-year-old hydrothermal vent precipitates in Quebec, Canada
The transition from non-living to living entities has never been observed experimentally.
