The Evolution of Fish and the Rise of Coal: A 100-Million-Year Journey
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Chapter 1: The Devonian Period and Its Aquatic Wonders
The current exploration spans a significant 100-million-year timeframe, specifically from 400 to 300 million years ago, encompassing the Devonian Period (419 to 359 million years ago).
Fish Flourishing
The Devonian is often referred to as the "Age of Fish," a title that certainly reflects the remarkable diversification of fish species, including the first recognizable sharks. However, this label overlooks the broader ecological landscape of the time, which was teeming with diverse marine life, such as ammonites, trilobites, coral reefs, sponge reefs, squid, and shellfish.
Tetrapod Evolution
Remarkably, the most significant fish of this era was a lobe-finned species that took a monumental step onto land approximately 385 million years ago. This creature is considered the ancestor of all four-limbed animals known today, which include amphibians, reptiles, mammals, and birds. In essence, this pioneering fish can be viewed as our ancestral figure.
Mass Extinction: Event Two
Around 375 million years ago, the oceans faced the second of Earth's five major extinction events, wiping out nearly half of all marine life within a few million years. The cause of this mass extinction is intriguing. Evidence suggests that it may have been linked to terrestrial events.
In the early Devonian, large fungi were replaced by numerous plants, including towering trees. These plants, equipped with innovations such as seeds and leaves, spread beyond riverbanks, forming extensive forests. Their roots disrupted the bedrock, releasing substantial nutrients into the sea, which fed marine algae and led to toxic algal blooms. If this theory holds true, trees might have been responsible for the demise of fish.
Glacial Impact
Additionally, these new forests acted as carbon sinks, absorbing carbon dioxide from the atmosphere. This shift initiated a significant glaciation event known as the Famennian, occurring around 360 million years ago. With this, the Devonian period drew to a close, paving the way for the Carboniferous Period (359 to 299 million years ago).
The first video, "The Complete History of the Earth: Carboniferous Period," explores the geological and biological developments during this era.
Chapter 2: The Carboniferous Period: Age of Amphibians and Coal
Amphibian Advancement
The Carboniferous is often dubbed the "Age of Amphibians," as fish fully transitioned into tetrapods. Nonetheless, this title minimizes the extraordinary developments of this period.
Supersized Creatures
During this era, dragonflies boasted wingspans comparable to human legs, and two-meter-long millipedes roamed the land. These gigantic insects thrived due to oxygen levels that were 50% to 70% higher than today, a result of the photosynthesis carried out by billions of newly evolved trees.
Coal Formation
However, this period could more aptly be named the "Age of Coal," as it was during the Carboniferous that 90% of Earth's coal reserves were formed. Vast swamps, situated around the humid equator, were home to these newly evolved trees. Upon their death, they became submerged in oxygen-deprived waters, eventually transforming into peat and later, coal.
Glaciation and Environmental Change
Around 305 million years ago, the entire rainforest ecosystem faced collapse. This was due to the persistent decrease in atmospheric carbon dioxide, which triggered another severe ice age, lowering sea levels by 100 meters. Consequently, the swamps dried up, the extensive forests vanished, and the climate shifted from humid to arid.
Thus concludes an incredibly eventful 100-million-year span in Earth's history. This article forms Part 44 of a 50-part series chronicling Earth's evolution.
The second video, "Does Coal Prove the Earth is Young?" presents a thought-provoking discussion regarding the implications of coal formation on geological timelines.
For further reading, check out Part 43: PLANTS AND FUNGI and Part 45: EXTINCTION. If you wish to explore the complete series, please consider following my work.