Jul 29 2011
I received the following question in my inbox this morning, and thought it would be a great topic for my blog today:
The dinosaurs were wiped out, along with much of the species of the Earth at some point. The few species that managed to survive eventually evolved and branched until something made it all the way to the modern human.
My question is – if humans were wiped off of the earth, would whatever primitive animal or insect that survives after our demise have no other choice than to evolve into something more intelligent than we are today? Or, is our human intellect the result of a very specific evolutionary path.
It makes sense to me that acquiring intelligence, at some point in the long, long process of evolution, would be one of the very few ways to get a leg up on your competition. The clever roaches live, ensure survival, pass along those smart genes. The next generation has an even higher bar, so only the most clever of those roaches survives, and so on.
Assume the only surviving species is a left undisturbed by the universe, and is coerced by its environment to compete and adapt until the end of time. Would intelligence be unavoidable?
This is a great question. Is the evolution of intelligence inevitable given the clear survival advantages of being smarter. This question is relevant to the Drake equation – on planets with life, how often will a technological intelligence arise?
From one perspective, we have one data point on this- Earth. We do not yet have any data on life on other worlds. Once we send our machines around exploring the galaxy (or however we do it) we may find countless worlds inhabited by the equivalent of bacteria or algae, but little multi-cellular life. Or we may find most planets with life occupied by one or more technological civilizations. Both extremes are compatible with the tiny amount of data we have (just Earth).
Perhaps, however, we can make some reasonable inferences from the history of life on Earth. Life arose very quickly after conditions on Earth allowed for it – a few hundred million years after the surface cooled. This suggest that life will tend to arise wherever conditions allow. However, physicists recently argued that this fact is still compatible with life being arbitrarily rare. True – but I think it does make it more likely that life is common.
This is the overarching question, however. How much can we infer from the history of life on Earth? Is Earth typical, or quirky? I will proceed based upon the reasonable assumption (but recognizing that it’s an assumption) that Earth is statistically typical, and does not represent a rare quirky example of how life develops and evolves.
Based on that assumption, life would seem to be common in the universe. However, it took over 3 billion years for life to develop multi-cellular forms. Multi-cellular life is about 550 million years old. Perhaps it will survive for another 500 million to 1 billion years. Therefore, if Earth is typical, life-bearing planets will have simple life for most of their history, and multi-cellular life for the final third or so. Perhaps many planets will not have stable enough conditions for life for long enough to develop complex multi-cellular life.
But now we are getting close to the e-mailer’s question – on worlds with multi-cellular life, how inevitable is intelligence, and as a subset of intelligence, how likely is a technological civilization? Following the logic above – not very.
Most of the evolutionary lineages on earth have not led to complex central nervous systems. All the invertebrates – insects, worms, jellies, sea stars, mollusks – have found adaptive strategies for survival that have not placed them on a course to technological intelligence. Given another billion years will the descendants of octupi evolve greater intelligence? Perhaps.
If we look at the first creatures to appear in the Cambrian explosion, basic body plans developed by chance. Only one of the 30 plus basic body plans (phyla) led to vertebrates and eventually developed complex central nervous systems. Perhaps on many worlds even with multi-cellular life there are no phyla that really have the potential to develop a technological intelligence.
Even among vertebrates, only in one tiny branch of one Family within one Order did technological intelligence arise. If this is any indication, then we can infer that the development of such intelligence is far from inevitable, but is extremely rare.
Whales and dolphins are fairly intelligent, but living in the ocean makes it unlikely they will develop advanced technology. This indicates that there are many different types of intelligence, and not all of them lead inevitably to technology.
A separate but related question, however, which the e-mailer mentions – is there a general tendency to evolve greater intelligence? Is intelligence a chance epiphenomenon, or can we expect a general trend toward greater intelligence over time? I think both views have merit. As I stated above, many multi-cellular lines do not seem to demonstrate a tendency for greater intelligence over time.
However, in those lines that have the basic anatomy and physiology (brains) that provide the potential for intelligence, there does appear to be a general trend over time for greater intelligence, at least in some of the lineages. I am not sure if the ungulates of today are smarter than the ungulates of 10 million years ago, but they may be.
Evolution does not follow a linear path toward greater intelligence (or any other quality). Adaptive radiation leads in many directions, and very few involve a significant increase in intelligence, and only some of those have the potential to lead to technology. The history of life on Earth would suggest that, while life itself may be common, complex life is less so, and technological intelligence is quite rare.
But that is where we run into the limits of our data – the fact that we have one data point makes it impossible to come to any firm conclusions. Technological intelligence may be rare in terms of lineages on Earth, but perhaps many planets with multicellular life, given that evolution will explore many body plans and adaptive strategies, will have one or more lineages that head in that direction.
I certainly would love to know the answer to these many questions. We are not going to figure it out on our own anytime soon, however. The best we can hope to do with our own exploration in my lifetime is to explore the solar system for life, such as in the oceans beneath the surface of Europa. We are nowhere close to exploring other stellar systems, however. Our only real hope there is SETI, or if another civilization contacts us directly.
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