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Regardless of billions of years of life on Earth, people first arose solely ~300,000 years in the past. It took all that point to make our arrival attainable.
It’s arduous to think about given how considerable and macroscopic life on Earth is in the present day, however for practically all of Earth’s historical past — upwards of three billion years and sure nearer to 4 — there have been no organisms extra advanced than a single-celled life type on our world. It wasn’t till the Earth itself was practically 4 billion years outdated that the appearance of enormous vegetation and animals lastly occurred. Complexity exploded round that point, as the mix of multicellularity, sexual copy, and different genetic advances introduced in regards to the Cambrian explosion. Many evolutionary modifications occurred over the subsequent 500 million years, with extinction occasions and choice pressures paving the best way for brand new types of life to come up, develop, and occupy ecological niches that immediately turned vacant.
After which, round 65 million years in the past, an epic occasion catapulted a category of small, largely scavenger animals — the mammals — right into a outstanding position that they had by no means occupied earlier than. As a catastrophic asteroid strike occurred, it worn out not solely the dinosaurs, however virtually each animal weighing over 25 kg (excepting leatherback sea turtles and a few crocodiles). This was Earth’s most up-to-date nice mass extinction, and left numerous niches unfilled in its wake. Mammals rose to prominence on land within the aftermath of this occasion, resulting in the primary people, which arose fewer than 1 million years in the past. Right here’s our story.
Our Photo voltaic System is and has at all times been a chaotic place, with objects reminiscent of asteroids, Kuiper belt objects, and Oort cloud objects consistently getting gravitationally perturbed by the planets and different objects of their vicinities. The extinction occasion that occurred on the finish of the Cretaceous interval was triggered by an enormous asteroid strike, as an asteroid someplace between 5 and 10 kilometers in diameter collided with Earth. The impression kicked up a layer of mud that settled all around the…
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