Trillions of ways life can evolve
I didn't know there were that many different species on Earth.
There aren't. That's the point.
Earth represents only a single environment where life has evolved and although quite diverse, can't even begin to describe what might be possible in a completely different environment.
Drake's Equation gives us only a tiny idea of just how wide spread life in the cosmos might be.
That is a very antiquated equation that was derived using only one data point. Nothing more than a guess disguised as a mathematical equation.
There are really two questions. The first is there life outside of our planet? We don't know because we only have one data point. The second question is if there is life elsewhere can it evolve into higher forms like here on earth, eventually (after 500 million years) leading to an intelligent species?
I have read the book "Rare Earth: Why Complex Life in the Universe is Uncommon in the Universe".
Rare Earth hypothesis - Wikipedia
Rare Earth hypothesis
According to the hypothesis, complex
extraterrestrial life is an improbable phenomenon and likely to be rare. The term "Rare Earth" originates from
Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), a book by
Peter Ward, a geologist and paleontologist, and
Donald E. Brownlee, an astronomer and astrobiologist, both faculty members at the
University of Washington.
Requirements for complex life
The Rare Earth hypothesis argues that the
evolution of biological complexity requires a host of fortuitous circumstances, such as a
galactic habitable zone, a central star and planetary system having the requisite character, the
circumstellar habitable zone, a right-sized terrestrial planet, the advantage of a gas giant guardian like Jupiter and a large
natural satellite, conditions needed to ensure the planet has a
magnetosphere and
plate tectonics, the chemistry of the
lithosphere,
atmosphere, and oceans, the role of "evolutionary pumps" such as massive
glaciation and rare
bolide impacts, and whatever led to the appearance of the
eukaryote cell,
sexual reproduction and the
Cambrian explosion of
animal,
plant, and
fungi phyla. The
evolution of human intelligence may have required yet further events, which are extremely unlikely to have happened were it not for the
Cretaceous–Paleogene extinction event 66 million years ago removing
dinosaurs as the dominant terrestrial
vertebrates.
In order for a small rocky planet to support complex life, Ward and Brownlee argue, the values of several variables must fall within narrow ranges.