4.54 billion years ago, the earth had just formed, and it was completely different from how we see it today.
It was a very inhospitable place with hellish temperatures hot enough to boil water. The atmosphere was devoid of oxygen, and the land was a barren wasteland devoid of any life. The oceans were non-existent as all the water was trapped in the form of gases.
By 3.8 billion years, the earth had cooled down enough for the gases to precipitate as rain. It rained for millions of years, eventually filling the vast basins and gorges, creating the very first oceans.
The oceans would remain empty for a while – with the very first signs of life emerging almost 540 million years later. The very first organism may have looked something like a bacteria, and its cell structure probably would have resembled one too.
From this group of unicellular organisms, life would go on to diversify into a multitude of lifeforms. However, some of these organisms would go extinct, and the niches they left was eventually replaced with other organisms. This cycle manifested itself over millions of years, creating an increasingly complex plethora of lifeforms.
For a long time, one of the most prominent groups of organisms that dominated the prehistoric landscape were the dinosaurs. They came in a lot of sizes and shapes, with the smallest one being no larger than a chicken and the largest one weighing a colossal 77 tons. Dinosaurs roamed the earth for millions of years until an asteroid impact, coupled with global climate change brought about their extinction. However, not all dinosaurs went extinct – the birds that we see today are technically the descendants of dinosaurs. They branched off from a family of dinosaurs called the theropods, which were characteristically bipedal. Today, this is evident as all modern birds are bipedal.
The next evolutionary milestone is the rise of the Great apes, which ultimately branched off into modern humans. However, evolution has not stopped there, as even to this day, humans are continually evolving. Though the changes are not quite perceptible, scientists speculate that an entirely new species of humans could arise over the next few millennia.
Explore other exciting topics from the human heart to cryptobiosis by registering at BYJU’S Biology
Comments