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- All cells come from a previous cell. (Cell theory, 1880)
- All cells formed by cell division have the same DNA, because it is just the same exact copy of genetic information.
- The zygote (the union between an egg and a sperm) comes from preexisting cells…they should follow an evolution track to know the origin of the first cell.

-The first cells must have arisen from non-living matter.

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Bugs born from dew drops on the leaves (Aristotle)

The Greek philosopher Aristotle was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water

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The Silphium plant sprouts  from the bare ground (Theoprastus)

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Mice, toads and cells can be created from water, air, or decaying matter. (Paracelsus)

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Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers. Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of  spontaneous generation.

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Lazzaro Spallanzani (1729–1799) and performed hundreds of carefully executed experiments using heated broth. As in Needham’s experiment, broth in sealed jars and unsealed jars was infused with plant and animal matter. Spallanzani’s results contradicted the findings of Needham: Heated but sealed flasks remained clear, without any signs of spontaneous growth, unless the flasks were subsequently opened to the air. This suggested that microbes were introduced into these flasks from the air. In response to Spallanzani’s findings, Needham argued that life originates from a “life force” that was destroyed during Spallanzani’s extended boiling. Any subsequent sealing of the flasks then prevented new life force from entering and causing

spontaneous generation

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Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it . His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of  spontaneous generation. He subsequently proposed that “life only comes from life.”

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Origin of the first cell from non-living matter

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Origin of the first cell from non-living matter

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Living cells may have evolved from inorganic matter over hundreds of millions of years in a series of steps. There are some hypotheses as to how this could have happened:

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2. Second
Assembly of carbon compounds into polymers.

The assembly of  carbon compounds into polymers requires a source of energy.

A possible site for the origin of the first carbon compounds is around deep-sea vents. These are cracks in the Earth's surface, characterized by gushing hot water carrying reduced inorganic chemicals such as iron sulphide. These chemicals represent readily accessible supplies of energy.

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3. Third
Formation of membranes.

If phospholipids or other amphipathic carbon compounds were among the first carbon compounds, they would have naturally assembled into bilayers. Experiments have shown that these bilayers readily form vesicles resembling the plasma membrane of a small cell. This would have allowed different internal chemistry from that of the surroundings to develop.

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1. First

The production of Carbon compounds like sugars and amino acids (1952) :

Scientists passed vapor through a mix of   Methane (CH4), Hydrogen (H2) and Ammonia (NH3), to represent atmospheric gases from the beginnings of the earth.  They used electric discharges as a source of energy. Amino acids were formed and other carbon compounds necessary for life.    Amino acids are the basic units of proteins.

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1952 (experiment by S. Miller and H. Urey)

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1952 (experiment by S. Miller and H. Urey)

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Stanley Miller and Harold performed an experiment to describe the origin of life on earth.

In 1952, Stanley Miller and Harold Urey combined water, methane, ammonia, and hydrogen in sealed vials in attempt to replicate Earth’s original atmosphere. They bombarded the vials with heat and continuous electrode sparks to simulate volcanic activity and lightening. Eventually, the reaction produced a number of amino acids – the building blocks of proteins and, by extension, life itself.

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4. Fourth
Development of a mechanism for inheritance (1967)

It is currently known that:

Living organisms are made up of genes made of DNA and with enzymes as catalysts.

Enzymes are required to be able to replicate DNA and pass it on to descendants.

Enzymes require genes in order to form.

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According to CSH (2012), the general idea that RNA replication preceded the appearance of protein synthesis was first proposed over 40 years ago (Woese, 1967; Crick 1968, Orgel 1968)

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There is the idea that on early Earth there existed an abundance of RNA life produced through prebiotic chemical reactions. In fact, in addition to carrying and translating genetic information, RNA is a catalyst, a molecule that increases the rate of a reaction without itself being consumed, meaning that a single RNA catalyst could have produced multiple living forms, which would have been advantageous during the rise of life on Earth.

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- Ribozymes are RNA molecules that can catalyze specific chemical reactions.
- RNA can copy itself, chop itself into pieces, and form these pieces make more RNA.

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The endosymbiotic theory sustains:

The mitochondrion  was a free prokaryote that developed the respiration process.

The mitochondrion where “eaten” by prokaryotes thru the process of endocytosis and instead of digesting them, they live inside their hostage cytoplasm.

The mitochondrion and the prokaryote organism had a symbiotic relationship helped by each other (mutualism).

The natural selection favored this kind of cells.

This theory also explains the formation of chloroplasts.

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Allot, A & Mindorff, D. (2014). Biology Course Companion. United Kingdom: Oxford University press.

Editions SM.SM .(2012) .

Endosymbiotic theory. Retrieved from: https://www.youtube.com/watch?v=RsaqJ2EwIKM

Endosymbiotic theory by the Amoeba Sisters. Retrieved from: https://www.youtube.com/watch?v=FGnS-Xk0ZqU&t=267s

Spontaneous generation of bacteria. Needham and Spallanzani. Retrieved from:

https://www.youtube.com/watch?v=MHZ9MLsepp8&t=482s

The wacky history of the cell theory. Retrieved from:

https://www.youtube.com/watch?v=4OpBylwH9DU&t=57s

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Libretexts. (2022, 5 marzo). 3.1: Spontaneous Generation. Biology LibreTexts. Retrieved 28 april 2023, from https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(OpenStax)/03%3A_The_Cell/3.01%3A_Spontaneous_Generation

Dussault, J. (2015, 23 junio). How can life emerge from nonliving matter? UNC scientists find new evidence. The Christian Science Monitor. Retrieved 28 april 2023, from https://www.csmonitor.com/Science/2015/0623/How-can-life-emerge-from-nonliving-matter-UNC-scientists-find-new-evidence

Foundations of Modern Cell Theory. (s. f.). Course Hero. Retrieved 28 april 2023, from https://www.coursehero.com/study-guides/microbiology/foundations-of-modern-cell-theory/}

Rogers, K. (2011, 29 agosto). Abiogenesis | Definition & Theory. Encyclopedia Britannica. Retrieved 28 april 2023, from https://www.britannica.com/science/abiogenesis

Boylan, M. (s. f.). Aristotle: Biology. Internet Encyclopedia of Philosophy. Retrieved 28 april 2023, from https://iep.utm.edu/aristotle-biology/