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Approximately 4.6 Billion years ago,
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our planet earth formed through a series of astronomical phenomena that enabled life to form.
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This inconceivable amount of time enabled the formation of biological molecules,
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which in turn, evolved to what we know as “Life” today.
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Now, let us ask,where did life even come from?
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And how did it become this complex system that leave scientists in mystery?
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In this video, we will explain the timeline and evolution of life on earth.
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Approximately 4.6 billion years ago,
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the planet earth was not as “habitable” compared to our current setting.
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This part of the history of earth was called the Hadean Eon.
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Although, it would be interesting to observe this
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since we would be able to see how the earth that we live on today was formed,
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it is not a pleasant environment to live on.
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Earth was consistently bombarded by asteroids and comets
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which in turn, heated the earth causing all water to convert into water vapor,
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thus the earliest atmosphere formed.
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This eon lasted for about 700 million years,
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thus we can imagine that the existence of life is really not possible at this time
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since all organisms would die due to the extremely high temperature of the planet earth.
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However, some scientists believe that these bombardments of heavenly bodies
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sparked the chemical building blocks of life,
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deoxyribonucleic acid
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or most commonly known as the DNA.
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Moreover, during this eon,
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the constant bombardment of the asteroids and comets as mentioned earlier
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caused repeated melting of the earth’s crust.
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Thus, no earth rocks from this time have survived.
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It is also during the Hadean Eon that the believed “Great Impact Hypothesis” occurred.
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This hypothesis tentatively explains the formation of the moon through the collision of a Mars-sized object to the forming Earth
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thus ejecting particles that in time,
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formed the moon through accretion and gravitational pull.
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The moon stayed in orbit with the earth since then.
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In conclusion,
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due to the harsh conditions of the earth back then,
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the existence of life in our planet earth occurred in the succeeding eons after the Hadean eon.
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The existence of the moon significantly affected the climate, oceans, and life on earth.
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In fact, due to the presence of the moon, the rotation of the earth slowed down significantly.
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From the original 6-hour rotation, it became a good long 24 hours.
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In addition to this, the moon significantly helped the earth to stop wobbling.
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Moreover, the different seasons in our time is caused by the moon.
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Because of its presence, the earth has a tilted orientation,
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making its revolution around the sun produce different seasons.
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In line with this, scientist have proposed that the climate of the earth stabilized during the Archaeon eon.
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After millions of years from the molten state of the earth,
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which caused water to evaporate and become vapour,
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during this eon, the water vapour condensed and formed liquid water
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due to the gradual decrease in the Earth’s temperature.
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In accordance with this phenomenon,
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when the earth became more suitable for life,
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primitive organisms were believed to have existed.
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An example of which are cyanobacteria,
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single celled microorganisms which release oxygen into the ocean as a waste product during their photosynthesis process.
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These led to an increase in the oxygen level of iron-rich oceans
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that paved way to the formation of banded iron on the seafloor.
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When all of the iron present in the ocean are consumed,
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excess oxygen are then released to the atmosphere,
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thus, the great oxygenation phenomenon occurred,
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which in turn, contributed to the increasing diversity of life in our planet.
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With the great oxygenation event caused by photosynthesis in cyanobacteria,
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an oxygenated atmosphere now ruled the Earth
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leading to the poisoning and subsequent extinction of chiefly-anaerobic microbes
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in what was called an oxygen crisis.
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With the abundance of methane in the atmosphere,
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there was the presence of an efficient greenhouse effect that warmed the Earth despite the less luminous young sun.
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However, with the emergence of oxygen and its combination with methane,
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carbon dioxide was formed.
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The greenhouse effect became weaker
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leading to an ice age which was termed as the “Snowball Earth”
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which lasted for hundreds of millions of years.
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From the dominance of anaerobic organisms,
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now, with an abundantly oxygen-filled atmosphere came the first aerobic eukaryotes.
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However, persistence of carbon dioxide limited their diversification.
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Dioxygen in the atmosphere led to creation of ozone and the thickening of the ozone layer.
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The ozone layer shielded the Earth from the harmful UV radiation
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and therefore life was able to diversify from shallow waters to the land
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in the end of the Proterozoic Eon and the Precambrian.
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Now we enter the Phanerozoic Eon and the Paleozoic Era with its 6 major periods.
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542 million years ago there was a sudden increase in oxygen levels
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causing the greatest boom of diversification of life in Earth’s history – known as the Cambrian explosion.
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Beginning the Paleozoic is the Cambrian period, known as the age of invertebrates.
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This is when the simple multicellular organisms like sponges, worms, and mollusks appeared in the Cambrian seas.
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These more complex organisms came about due to the presence of sufficient oxygen to maintain their energy needs
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when it came to evolving more complex structures such as shells and skeletons.
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As life continued to get diverse,
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485 million years ago entered the Ordovician period,
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when most of the world’s land was collect in the supercontinent Gondwana.
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Marine invertebrates and early vertebrates flourished in this period.
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The appearance of the first life that can thrive in land came in the transition to the next period 443 million years ago,
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the Silurian period.
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This is when the first simple land ecosystems appeared.
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In entering the Devonian period 419 million years ago,
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the first fish with jaws and backbones appeared.
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With the huge diversity of fish that sprung in this period,
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it was fittingly named as the Age of Fish.
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359 million years ago, large forests grew which also led to extreme oxygen levels
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an ideal environment for arthropods or large insects was created.
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Amphibians also flourished around this time.
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The evolution of some organisms to produce amniotic eggs
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made possible birthing on land and a rapid expansion of diversity.
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The large forests in the Carboniferous ended up as the coal deposits we use today.
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299 million years ago then came the last period of the Paleozoic, the Permian period.
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This is when the first large vertebrates dominated the land.
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The richness of plants in the surroundings and the evolution of stomachs capable of digesting such plants
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allowed herbivores to prosper in this age.
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With the Paleozoic beginning with the Cambrian explosion,
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similarly it ended with a magnificent explosion.
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However, in the process it took with it most of the life created in the Paleozoic.
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The Permian-Triassic Extinction is the largest mass extinction in Earth’s history
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killing 96% of all marine species and 70% of all terrestrial vertebrates.
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This event is also known as “The Great Dying”
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which was probably caused by an explosion of huge volcanic plume or perhaps the cataclysmic impact of a major asteroid.
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As Earth's climate continues to shift from cold to dry,
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amphibians that reside on rainforest lands die as the temperature rises and the rainforest collapses.
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This event is known as Carboniferous Rainforest collapse.
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Reptiles on the other hand were able to adapt and dominate the cool and drier land.
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They eventually evolved and increased in number.
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The Mesozoic, or "Middle Life" Era.
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Life diversified rapidly and giant reptiles, dinosaurs and other monstrous beasts roamed the Earth.
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For the next 160 million years, dinosaurs were the dominant land vertebrates on Earth.
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The dinosaurs adapted to their ecosystems.
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Some adapted as herbivores and some as carnivores.
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The union of the dinosaurs produced hybridization of dinosaurs.
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Spread of seeded plants resulted in more oxygen and less carbon,
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providing a more suitable habitat.
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The supercontinent Pangea eventually tore apart into smaller continents and drifted the dinosaurs apart.
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This is evident to the dinosaur fossils found on separate continents.
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A Dark Nebula collided with our solar system, covering the heat from the sun.
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Global cooling damages the ecosystem and kills many of its inhabitants.
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Finally, a meteorite struck the earth's seabed
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Creating a massive explosion that produced intense heat and deadly wind of dust across the globe leading to dinosaurs' extinction.
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The start of the Cenozoic era signaled the end of the dinosaurs.
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A 6-mile wide asteroid fell from the sky and obliterated most of the reigning reptiles.
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The fall caused a massive dust cloud that resulted to the decrease of the Earth’s temperature.
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This change in the climate the dinosaurs were not used to ensured their total destruction.
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Mammalian creatures were existent before the start of the Cenozoic Era.
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They were small and often hid from the dinosaurs that roamed the earth.
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The extinction of the dinosaurs let them emerge from their hiding and grew bigger to now dominate the land.
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Early Primates who emerged from the line of mammalian creatures stayed near their primary food sources, the trees.
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As time passed, trees became scarcer while grass grew more prolifically.
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They were forced to walk and look for new food sources.
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It is theorized that to see beyond the tall grass, ancient apes slowly evolved to walk on two legs and stand tall.
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They slowly mastered how to use their now hands from walking on four legs.
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Hominids or the early proto human learned how to wield objects in the form of sharpened silicon rocks.
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They wielded tools and by the Stone Age fire was discovered.
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This enabled humans to cook their food and gain more energy from their hunts.
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We slowly learned how to make complex sounds and reach the point of communication.
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The discovery of farming resulted into a shift from nomadic and slowly to community building.
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Through the social structures we were able to progress as a race and reach the modern man.
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The life on earth has come a long way.
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From a simple single-celled organism to the complex structures found in each living being.
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We have come a long way.
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Throughout the years we slowly developed our technology to reach this modern era of science and advancement.
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In the years to come, what developments could the modern man encounter that could drive humanity to a new era?
