This is a fascinating question! However, I think you are making a mistake in estimating the lower bound:
The fact that chimps are removed by 7 million years of evolution (Wikipedia says 4-13 million) rests on the assumptions that:
Chimpanzees needed these 7 million years to evolve to their current level of intelligence.
Instead, their evolution could have contained multiple intervals of random length with no changes to intelligence. This implies that chimpanzees could have evolved from our common ancestor to their current level of intelligence much faster or much slower than 7 million years.
The time since our divergence with chimpanzees is indicative of how long it takes from their level of intelligence to ours.
I am not quite sure what to think of this. I assume your reasoning is “it took us 7 million years to evolve to our current level of intelligence from the common ancestor, and chimpanzees probably did not lose intelligence in those 7 million years, so the starting conditions are at least as favorable as they were 7 million years ago.” This might be right. On the other hand, evolutionary paths are difficult to understand and maybe chimps developed in some way that makes it unlikely to evolve into a technologically advanced society. Nonetheless, this doesn’t seem the case because they do show traits beneficial to evolution of higher intelligence, e.g. tool use, social structure, and eating meat.
All in all, thinking about this I keep coming back to the question: how contingent is evolution instead of directional when we look at intellectual and social capability? There seems to be disagreement here in the field of evolutionary biology, even though there are many different evolutionary branches where intelligence evolved and increased.
Also, you have given the time periods when a next civilisation might arise if it arises, but how likely do you think that it arises?
Surely, 7 million years estimation has big uncertainty, and it could be shorter, but unlikely shorter than 1 million year, as chimps have to undergo important anatomic changes to become human-like: they need to have larger heads, different walking and hanging anatomy, different voice anatomy etc, and selection for such anatomic changes was slow in humans. Also, most catastrophes which will kill humans will probably kill chimps too, as they are already endangered species in many locations, and orangutangs are on the brink of extinction in natural habitats.
However, there is another option for the quick evolution of intelligence after humans, that is domesticated animals, firstly dogs. They have been selected for many human-like traits, including understanding voice commands.
Chimps in zoos also were trained to speak some rudimentary forms of gesture language and trained their children to do so. If they preserve these skills, they could evolve much quicker.
This is a fascinating question! However, I think you are making a mistake in estimating the lower bound: The fact that chimps are removed by 7 million years of evolution (Wikipedia says 4-13 million) rests on the assumptions that:
Chimpanzees needed these 7 million years to evolve to their current level of intelligence. Instead, their evolution could have contained multiple intervals of random length with no changes to intelligence. This implies that chimpanzees could have evolved from our common ancestor to their current level of intelligence much faster or much slower than 7 million years.
The time since our divergence with chimpanzees is indicative of how long it takes from their level of intelligence to ours. I am not quite sure what to think of this. I assume your reasoning is “it took us 7 million years to evolve to our current level of intelligence from the common ancestor, and chimpanzees probably did not lose intelligence in those 7 million years, so the starting conditions are at least as favorable as they were 7 million years ago.” This might be right. On the other hand, evolutionary paths are difficult to understand and maybe chimps developed in some way that makes it unlikely to evolve into a technologically advanced society. Nonetheless, this doesn’t seem the case because they do show traits beneficial to evolution of higher intelligence, e.g. tool use, social structure, and eating meat. All in all, thinking about this I keep coming back to the question: how contingent is evolution instead of directional when we look at intellectual and social capability? There seems to be disagreement here in the field of evolutionary biology, even though there are many different evolutionary branches where intelligence evolved and increased.
Also, you have given the time periods when a next civilisation might arise if it arises, but how likely do you think that it arises?
Surely, 7 million years estimation has big uncertainty, and it could be shorter, but unlikely shorter than 1 million year, as chimps have to undergo important anatomic changes to become human-like: they need to have larger heads, different walking and hanging anatomy, different voice anatomy etc, and selection for such anatomic changes was slow in humans. Also, most catastrophes which will kill humans will probably kill chimps too, as they are already endangered species in many locations, and orangutangs are on the brink of extinction in natural habitats.
However, there is another option for the quick evolution of intelligence after humans, that is domesticated animals, firstly dogs. They have been selected for many human-like traits, including understanding voice commands.
Chimps in zoos also were trained to speak some rudimentary forms of gesture language and trained their children to do so. If they preserve these skills, they could evolve much quicker.