Events that culminated in the appearance of modern humans

Events that culminated in the appearance of modern humans

ORIGIN OF LIFE TO THE HOMO SAPIENS

origin of the solar system

origin of planet Earth

origin of the universe

Origin of life

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Big Bang & Cosmic Inflation

The Big Bang theory holds that the universe began after a big explosion 13.81 billion years ago. Before this, all the matter in the universe today was concentrated in an extremely small point called a singularity. The massive explosion that this point experienced marked the beginning of the expansion of the universe. The small particles clump together. And they formed the atoms. Then those atoms grouped together. After a long time, the atoms came together to form stars and galaxies. The first stars created larger atoms and groups of atoms. From there more stars were born. At the same time, galaxies collided and clustered with each other. As new stars were born and others died, things like asteroids, comets, planets, and black holes formed.

The theory of cosmic inflation is a proposal from theoretical physics that explains the rapid expansion of the universe in its early moments. This theory states that the universe expanded exponentially for a fraction of a second after the Big Bang. consists of an accelerated phase of expansion that occurred in the early universe at very high energy. This theory not only answers the main problems of the Big Bang, but also proposes a mechanism for a formation structure based on general relativity and quantum mechanics. Inflation theory proposes a period of extremely rapid expansion of the universe before a more gradual expansion. At this time, the energy density of the universe is dominated by a cosmological constant of vacuum energy that then decayed to form the matter and radiation observed in the universe today.

Nebular Hypothesis

around young stars, like those in the Orion Nebula, resembling the early solar system. The nebular hypothesis explains the solar system's formation in these steps: 1. A rotating cloud of gas and dust (nebula) collapses due to gravity. 2. The nebula flattens into a spinning disk, with the Sun forming at the center. 3. Dust and gas in the disk clump into planetesimals, which grow into planets. 4. Solar winds clear leftover gas and dust, leaving the Sun, planets, and smaller bodies.

The nebular hypothesis is a widely accepted explanation for the formation and evolution of the solar system. It was first proposed in the 18th century by Immanuel Kant and Pierre-Simon Laplace, and has since been refined with modern astronomical observations and theoretical advancements. The nebular hypothesis suggests that the solar system formed from a giant rotating cloud of gas and dust, called a solar nebula, approximately 4.6 billion years ago. Under the influence of gravity, this cloud underwent a series of physical and chemical transformations, leading to the creation of the Sun, planets, moons, and other solar system objects. Astronomers have observed protoplanetary disks

Formation of earth

simple organic molecules through a series of chemical reactions. The molecules, possibly formed in the oceans or brought by meteorites, underwent further reactions to create more complex compounds, eventually leading to the first simple life forms. Experiments such as The Miller-Urey experiment gives legitimacy to this theory as in 1952 it demonstrated that amino acids, the building blocks of life, could be synthesized from inorganic compounds under conditions thought to resemble those of early Earth.

Approximately 4.54 billion years ago cloud of gas and dust left over from the formation of the Sun went through the process known as accretion, clumping together to gradually form the Earth. During its early history, Earth had frequent collisions with celestial bodies, causing extreme volcanism, high temperatures and the formation of a primordial atmosphere through volcanic outgassing. As Earth cooled, a solid crust formed and water vapor condensed to create oceans. These new conditions gave way for the emergence of life. One leading hypothesis for the origin of life is abiogenesis, which suggests that life arose from

Theories of the origin of life

Spontaneous Generation: Life arises from inorganic matter. Proposed by Aristotle, disproven by Louis Pasteur in 1859.

Coacervates: Life originated from lipid molecules forming simple structures. Proposed by Oparin and Haldane; evidence exists but lacks definitive proof.

Panspermia: Life originated in space and arrived on Earth. Coined by Svante Arrhenius; lacks evidence for the origin of life itself.

Primitive Bacteria: Organic compounds in oceans formed early life, supported by the Miller-Urey experiment.

Abiotic Synthesis: Organic molecules form from inorganic compounds, potentially leading to life. Supported by the Miller-Urey experiment but not definitively proven.

Endosymbiotic Theory: Eukaryotic cells evolved from symbiosis between prokaryotes. Strong evidence includes organelles with their own DNA. Proposed by Konstantin Mereschkowski and popularized by Lynn Margulis.

Hydrothermal Theory: Organic molecules formed in hydrothermal vents. Proposed by Günter Wächtershäuser; supported by some evidence but unproven.

Mass Extinction (~66 million years ago): A catastrophic event ended non-avian dinosaurs, paving the way for mammal diversification. Cenozoic Era (66 million years ago - present): Primates appeared (~55 million years ago), eventually evolving into hominids, the ancestors of humans. Emergence of Homo (~2.5 million years ago): Species like Homo habilis (tool users) and Homo erectus (migrators) laid the foundation for modern humans. Homo sapiens (~300,000 years ago): Modern humans evolved with advanced cognition, language, and culture, thriving globally and creating complex societies.

First Life Forms (~3.5 billion years ago): Unicellular prokaryotes (bacteria) emerged, dominating for billions of years. Eukaryotes arose later through symbiosis, leading to complex cells. Multicellular Life (~1.5 billion years ago): Eukaryotes began forming multicellular organisms, enabling the development of complex structures and diversity. Paleozoic Era (541–252 million years ago): Marine animals, terrestrial plants, amphibians, and reptiles appeared, marking the transition of life from water to land. Mesozoic Era (252–66 million years ago): Dinosaurs dominated, alongside the first mammals and birds. Flowering plants diversified.