Intelligent life on Earth appeared in a delicately balanced environment, formed following a number of global catastrophes, which have prompted some to brand them strokes of good luck for humankind. What exactly caused us to be so lucky?
Birth of the Moon
Our planet’s satellite, the Moon, which drastically impacts life on Earth, was born 4.5 billion years ago as a result of a major catastrophe, scientists concluded after studying its soil. In the young and messy Solar system, newly-formed Earth allegedly collided with a Mars-sized planed, sometimes referred to as Theia. Although a piece of Earth was lost and our planet changed its axis, the unwelcome guest was shattered.
The resulting debris from the collision formed the Moon as the gravitation pulled them together about one million years later. While the tilted axis contributed to the appearance of four seasons, the Moon and its pull kept the iron core inside Earth from stiffening. This enables our planet to have an atmosphere of oxygen, which shields us from ultra-violet radiation, and protects us from asteroids. Without all this, life on Earth, as we know it, would be hardly imaginable.
Earth has also had several periods of extremely low temperatures, with the two coldest eras particulary important for the development of life. The first such severe period, called the Huronian glaciation (or Makganyene glaciation), happened 2.4 billion years ago and lasted 300 million years. Although life existed around that time, it was limited to micro-organisms. So these bacteria managed to survive to develop into more complicated organisms.
Another major glaciation, which allegedly came 720–635 million years ago when sponge-like creatures and sea bacteria existed, is sarcastically called the Snowball Earth. As one of the hypotheses suggests, the temperature reached -43 °С around the Equator. However, the alleged puddles at the Equator and near mountain tops remained, which helped these creatures to survive – what their chances were if this period lasted longer, we can only guess.
Siberian Traps Born
Another major catastrophe, which, on the contrary, heated up Earth, happened 252 million years ago. At that time, the planet witnessed a massive eruptive event in what is currently Siberia, which was located in the north of the ancient super-continent Pangaea. More than 5 million cubic metres of basalt were brought onto the surface, forming mesmerising landscapes, along with ashes and poisonous gases.
It coincided with the massive extinction period when 96% of marine creatures and 70% terrestrial vertebral animals disappeared, as well as 83% of insect species. This event was called the Permian extinction. However, as scientists suggest, this was not the only effect of the eruption. The latter likely triggered other biosphere processes, steering evolution on the course that eventually led to the appearance of humans.
Another mass extinction period came 66 million years ago, wiping out the creatures which had ruled Earth for 250 million years, dinosaurs. They along with other big and medium-sized animals and three-quarters of all existing plant and animal species vanished in the Cretaceous–Paleogene extinction event, allegedly caused by an asteroid strike.