I don’t deny that if you go back into the PreCambrian period three billion years ago you only had bacteria, and now you have flamingos, hippopotamuses, and people. In a sense that is progressive. But, there is no story of slow, steady, increasing, gradual, accumulated advance. What you have is one great burp called the Cambrian explosion 600 million years ago, in which virtually all the major groups of organisms evolved, and the history of life since then, as I see it, has been largely a running of variations on these basic themes.
I do not see gradual, predictable, accumulative progress in the history of life. I do not think you had expected that! Evolution is about local adaptation, it is not about cosmic advance. I think the idea of progress is very much a cultural bias, based on the desire to read the history of nature as the history of perfection, gradually increasing and leading to the late evolution of humans as dominant, and dominating creatures by right.
Let me give you the best example of how you must look at the complexity of human intelligence as a lucky random event, and not as a predictable consequence of accumulated progress. Most people do not know that Mammals evolved in the late Triassic Period that is about 200 million years ago. Mammals lived for about 100 million years that is two thirds of their existence, as tiny little creatures in the interstices of the dinosaur’s world. They did not dominate, they did not get bigger, they lived like little rat like creatures. Then along comes a cosmic catastrophe at the end of the Cretaceous Period that wipes out the dinosaurs and mammals take over, because some space is cleared out.
Now suppose that had not happened. Dinosaurs had lived for 100 million years and mammals never got anywhere. It has only been 65 million years since and but for that, comet showers or whatever, dinosaurs would still dominate and mammals would still be tiny creatures. For 100 million years, dinosaurs were not moving towards intelligence. I think that they would be now what they were then. And we would not be sitting here, our potential ancestors would still be little rats scurrying around the dinosaurs.
There is no predictable progress to human intelligence. A chance comet shower may have been an indisputable condition, leading to our own accidental evolution. Now, I do look at human evolution as glorious. Consciousness is the greatest invention in the history of life, it has allowed life to become aware of itself and to recognise the facts of its own evolution, at least in one species of animal. But, it sure as hell wasn’t a predictable consequence of universal progress.
One interesting political or social spin off to the ‘Theory of Extinction of the Dinosaurs’ (and other past extinctions) by comet showers, is the development of the ‘Nuclear Winter’ scenario as a powerful additional argument against nuclear war. It is fascinating that the scenario envisaged in nuclear winter, getting very cold, and dark, thanks to a dust cloud thrown aloft by nuclear explosions, is in fact the same scenario that many people are proposing for the Cretaceous Extinctions 64 million years ago that wiped out the dinosaurs. It was a recognition that an asteroid packs more megatonnage than all the world’s nuclear weapons, which led to that scenario. I often think it is a delicious irony that perhaps it is the recognition of the same scenario, which is one small aid in a larger struggle that would contribute to our own survival now.
If we did manage to wipe ourselves out. I see no reason to predict that consciousness would evolve again. I do not want to say, "never", because there are billions of years to go before the Sun explodes. But, I see no reason to predict the evolution of consciousness again as I think it was a glorious, unpredictable, evolutionary accident. There is no mammalian lineage, which seems to be moving in that direction. We have been around for a long time, but that is no reason to think that the great apes would be moving in that direction, they have been around a long time. So, I think, it probably would not happen. So, we better stick around if we like the invention.
Condensed from an interview with Stephen Jay Gould, Professor at Harvard University. He teaches Geology, Biology, and the History of Science.