Robin Hanson discussed great filters in regards to the Fermi Paradox. Humanity seems to have a non-trivial chance of expanding to fill the universe with lasting life. But the fact that space near us seems dead now tells us that any given piece of dead matter faces an astronomically low chance of begating such a future. There thus exists a great filter between death and expanding lasting life, and humanity faces the ominous question: how far along this filter[s] are we?
Consider our best-guess evolutionary path to an explosion which leads to visible colonization of most of the visible universe:
1. The right star system (including organics)
2. Reproductive something (e.g. RNA)
3. Simple (prokaryotic) single-cell life
4. Complex (archaeatic and eukaryotic) single-cell life
5. Sexual reproduction
6. Multi-cell life
7. Tool-using animals with big brains
8. Where we are now
9. Colonization explosion
Around 70,000 B.C., a volcano called Toba, on Sumatra, in Indonesia went off, blowing roughly 650 miles of vaporized rock into the air. It is the largest volcanic eruption we know of, dwarfing everything else… It was probably the second largest known explosive eruption over the last 450 million years.
The Toba catastrophe theory suggests that a bottleneck of the human population occurred c. 70,000 years ago, proposing that the human population was reduced to perhaps 10,000 individuals when the Toba supervolcano in Indonesia erupted and triggered a major environmental change. The theory is based on geological evidences of sudden climate change and on coalescence evidences of some genes (including mitochondrial DNA, Y-chromosome and some nuclear genes) and the relatively low level of genetic variation with humans.
The Toba eruption dropped roughly six centimeters of ash — the layer can still be seen on land — over all of South Asia, the Indian Ocean, the Arabian and South China Sea. The Toba eruption was three times bigger than the Yellowstone eruption.
With so much ash, dust and vapor in the air, Sam Kean says it’s a safe guess that Toba “dimmed the sun for six years, disrupted seasonal rains, choked off streams and scattered whole cubic miles of hot ash (imagine wading through a giant ashtray) across acres and acres of plants.” Berries, fruits, trees, African game became scarce; early humans, living in East Africa just across the Indian Ocean from Mount Toba, probably starved, or at least, he says, “It’s not hard to imagine the population plummeting.”
Habitable planets with more frequent Volcanoes and bigger Volcanoes could prevent space faring civilizations
The Toba example suggest that an otherwise habitable planet with more frequent volcanoes and bigger super-volcanoes could prevent space faring civilizations from having the time to develop.
We also have the asteroid that wiped out the dinosaurs. Again a solar system with more frequent asteroids could be prevented from having a safe period to develop a civilization with space faring capability.
Also, during the dips in population with population bottlenecks, if the other animals or environment were more dangerous then more of the population dips would lead to more extinctions.
The more challenges and close calls that were overcome in human history, then the more likely humans have already overcome great filters and the less likely there are more great filters to overcome in our future.
As usual with really ancient history and human evolution, there is a lot of controversy and disputes around how big the Toba volcano was and whether people just moved or whether the population drop was localized to Africa and asia.
The idea that humans nearly became extinct 75,000 ago because of a super-volcano eruption is not supported by new data from Africa, scientists say. An Oxford University-led team examined ancient sediments in Lake Malawi for traces of this climate catastrophe. It could find none.
Still on another habitable planet, if there were bigger supervolcanoes or more asteroids that disrupt the development of intelligent species and civilizations then they would not be able to achieve space faring capability.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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