First, we can't really say that human level intelligence has evolved only once. Pretty sure it has evolved only once and got as far as high technology. Or rather several times in related hominids, all except one of which went extinct.
That all the other intelligent hominids except for us went extinct doesn't suggest it is such a huge survival advantage just to be intelligent. For a long time, although humans had primitive technology, they weren't that numerous.
But - could be that there were creatures in the past as intelligent as us. For instance the second most intelligent creature after humans, some would say, is the grey parrot. Or others might say elephant or dolphin. Anyway - they wouldn't be that obvious choices for intelligent creatures in the fossil record.
So what if some of the creatures in the past were as intelligent as humans? Would we know? Assume that they develop only primitive technology - maybe some basic tool using, and lived millions of years ago. If they were dolphin like creatures with no hands, or creatures like parrots with only limited ability to make things by hand, they might leave almost no relics of their presence at all, and what they did leave may not be recognized as technology - just a heap of sticks for instance.
Then - it's only a few hundred million years, perhaps a billion years depending, since the first multi-cellular life. So - what if intelligence is something that is both rare and slow to evolve? Maybe it needs several hundred million years of evolution to get to our stage - or maybe it evolves only once every hundred million years.
Modern animals have larger brains, generally, than dinosaurs of the same size. So might be that there is a general trend in evolution towards a wider spectrum of brain size - gradually evolution "figures out" how to do large brains in various creatures and for them to be able to survive.
If so, we might well be the first of many civilizations that will evolve over the next half billion years.
See also my science20 article: End Of All Life On Earth - A Billion Years From Now - Can It Be Avoided - And Who Will Be Here Then?
which originated in my quora answer to: What are the odds that a viable population of humankind will escape to another planet before the earth becomes uninhabitable?
That all the other intelligent hominids except for us went extinct doesn't suggest it is such a huge survival advantage just to be intelligent. For a long time, although humans had primitive technology, they weren't that numerous.
But - could be that there were creatures in the past as intelligent as us. For instance the second most intelligent creature after humans, some would say, is the grey parrot. Or others might say elephant or dolphin. Anyway - they wouldn't be that obvious choices for intelligent creatures in the fossil record.
So what if some of the creatures in the past were as intelligent as humans? Would we know? Assume that they develop only primitive technology - maybe some basic tool using, and lived millions of years ago. If they were dolphin like creatures with no hands, or creatures like parrots with only limited ability to make things by hand, they might leave almost no relics of their presence at all, and what they did leave may not be recognized as technology - just a heap of sticks for instance.
Then - it's only a few hundred million years, perhaps a billion years depending, since the first multi-cellular life. So - what if intelligence is something that is both rare and slow to evolve? Maybe it needs several hundred million years of evolution to get to our stage - or maybe it evolves only once every hundred million years.
Modern animals have larger brains, generally, than dinosaurs of the same size. So might be that there is a general trend in evolution towards a wider spectrum of brain size - gradually evolution "figures out" how to do large brains in various creatures and for them to be able to survive.
If so, we might well be the first of many civilizations that will evolve over the next half billion years.
See also my science20 article: End Of All Life On Earth - A Billion Years From Now - Can It Be Avoided - And Who Will Be Here Then?
which originated in my quora answer to: What are the odds that a viable population of humankind will escape to another planet before the earth becomes uninhabitable?
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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