Why Now?

Asking the question about whether there could have been a more advanced civilization of humans that was eliminated in a catastrophe, or related questions, leads to some deeper ones. Why did intelligent humans evolve at the time they did? Why didn't we evolve into city-living, culture-appreciating, educated, adept, clever humans two hundred thousand years ago? What delayed our approach? Why weren't we delayed another hundred thousand or two years? Why now?

One way of looking at this is to examine the preconditions for the final leap of evolution, to thinking brains and everything they required, and see when they arose for the first time. The simplistic solution is to just make a list, accurate as possible, of what steps led to humans and see why one of them couldn't have happened earlier.

One detail needed to follow this approach is to decide just where on the taxonomy of animals intelligence could have arisen. The pat answer is that we needed thermally regulating bodies so our brains didn't turn off in the winter. Why is this true? What about evolving in a region with fairly constant temperatures over the year? Perhaps it is a day/night temperature difference that excluded reptiles from becoming intelligent. Suppose some lizard had a complex brain, but could only think during the day when temperatures were warmer; why is this an impossibility? During colder temperatures only the lower brain stem, which is what today's reptiles have, was working. That part would allow the reptile to live like other dumber reptiles, except when temperatures got warmer, and then it could think great thoughts.

If we cannot determine some incontrovertible reason why reptiles couldn't have become more intelligent, the boundary of time when intelligence could have started is pushed back, hundreds of millions of years, when, supposedly, reptile species ruled the entire planet. We should ask: what good would being able to think more complex thoughts do for a reptile? Their ability to survive and reproduce depends on their visual skills, their speed, their ability to recognize hiding places, their ability to capture prey using body and head muscle linkages with eye coordination, and perhaps a few other things. Nowhere in this list is anything that a complex thought might help. Compare that with chimpanzee-like species which could begin to use found objects and then shaped objects as tools. Tool-using elevated species from chimpanzee level to human level. Current eptiles don't have the physiology for that.

So, could we have reptiles of millions of years ago, those who were living in forests, take an evolutionary jump to climbing trees and developing opposing thumbs and dextrous hands? If evolution could do this, why not, over another million years of evolution, could they not develop thermal regulation to some extent? Thermal regulation requires energy, and could reptiles become better hunters or more complete omnivores, and simply follow the pathway to intelligence that proto-chimpanzees would follow millions of years later? Why weren't the steps needed for intelligence, whatever they might have included, completed long ago, in the millions of years scale.

Perhaps evolution couldn't make the total number of jumps needed for this, simultaneously. Was the jungle many millions of years ago more hostile to the growth of intelligence that the forests of a few hundred thousand years ago? What about hands? Some animals climb trees using their claws, which penetrate into the bark or catch on irregularities in the bark of trees, and evolve so that this method improves, as opposed to developing grasping hands, which is a totally different evolutionary path.

Without grasping hands, evolution couldn't take one of its sideways steps. A sideways step in evolution is when a species either mutates its genome by moving one section to another place, perhaps copying it there, which then allows the species access to some new capability, not related to the one for which the genes had evolved for. We can think of the software side of evolution, which is what happens when one generation imparts some wisdom to the next one, which allows the newer generation to use its mental and physical capabilities in a task that it wouldn't have, without the training.

What else in evolutionary pressure serves to force hands to develop? If the species lives on fruits and other pickable objects, hands might be useful here. Alternately, if the animal simply eats leaves and flowers for nourishment, then hands don't play much of a role and wouldn't be selected for in the evolutionary process. Fruit provides more concentrated nourishment that leaves, as do seeds and some roots. Was food selection the problem that kept reptiles from becoming intelligent millions of years ago?

This doesn't sound correct. Why couldn't reptiles evolve to eat fruit and seeds, if primates could? Were there fruits around millions of years ago in the equivalent of forests?

Perhaps the question should be asked in a completely different way. How do we know that some lizard species did not develop intelligence of some sort two hundred million years ago? Would there be anything detectable this many years after they became extinct? Perhaps the intelligent lizards lasted a million years and build cities. What kind of rubble lasts two hundred million years? Do we know how to do excavations to figure out the answer to this question?

One thing we do have is fossils. Fossils occur when some animal does some stupid thing and gets caught in some mud and dies and then the mud turns to stone. Because of some perversity of nature, braincases are not often found in fossils. But recently some have.

To be intelligent, one needs a large brain, measured in terms of brainweight to bodyweight. Some recent finds of reptiles raises the possibility that some of them may have larger brains that has been expected by the earlier-discovered fossils. If we assume that civilized reptiles two hundred million years ago managed to largely avoid getting stuck in mud pits and turned into fossils, then their absence in our dinosaur skeletal displays in the different natural history museums around the world is understandable.

What else might be left behind from a civilizatin of intelligent creatures that lived for a million years and died out two hundred million years ago? What might get buried and refound that would last two hundred million years? For early human civilizations, we look at burial mounds. These are put together in the first few thousand years of civilization, and then everybody stops doing it. Inside these burial mounds there are gold ornaments and jewels, which might be contenders for enduring the forces of nature for millions of years. Would a civilization that lasted much longer not simply collect these things from their own archaic burial mounds and put them in a museum? And since the Earth changes its profile in much shorter times that two hundred million years, moving dirt and rock and lava and water and any materials around on the planetary surface, how could we expect anything from an ancient city to survive. Maybe they invented materials that were more durable than concrete? Concrete might be good for tens of thousands of years, if no earthquake or flood gets to it. What is left after a short time such as a hundred thousand years? Rubble. Maybe there might be some chemical test to see if some rubble we find has some unique features? Rubble near the surface probably wouldn't stay in one place, however.

One thing we can detect for long periods, in very unique situations, is the materials embedded in layers of rock. That is how we suspect a large asteroid hit the planet some 65 million years ago, from the thin layer of iridium-rich deposits all around the world. Would the lizard civilization have put something into their air which would be detectable? It is very hard to think of any possibilities in this area.

The conclusion is beginning to look inescapable. There is no way to tell if we are the first intelligent species to emerge on Earth. All the hubbub that goes on about aliens on other planets coming to visit us might be expanded to ask if there were some 'aliens', of the homegrown variety, right here already. If it could have happened once, maybe it could have happened twice or more times. All of these things would leave no evidence. One result of realizing we might be the tenth intelligent species on Earth rather than the first is that we really don't have a good understanding of evolution yet. Maybe there are clues buried in the genomes of the organisms of Earth that indicate something intelligent was around a very long time before us. It is certainly not clear how this might happen, but we need to grasp at straws to answer this question.

Ancient Civilizations

Common belief here on Earth is that our civilization has been continuously improving since the human species came into existence. It has been a steady sequence of more population, more technology, more areas inhabited, more organization, more culture and so on. With that as our history, it is easy to project onto possible alien civilizations on exoplanets that they too had a uniformly improving history. Then some comparisons can be made, some calculations, and some predictions. That has been the basis of this blog.

What if this is all wrong? What if there have been one or more civilizations on Earth which were wiped out by one or more catastrophes? There are at least two questions that immediately spring up. One is about the evidence that might indicate this is at least possible and not ruled out by everything archeologists, geologists, and other scientists have collected and interpreted. The other is, provided the answer to the first is that the evidence for the simple single rise of civilization is not wholly compelling, what does this mean about potential alien civilizations? If our planet had one or even a series of catastrophes, wiping out mankind down to the hunter-gatherer level, and then mankind built up a following civilization virtually from scratch, maybe this happened on exoplanets as well. 

Why even consider this? There are some scientists and others who see something in the evidence available to us, overlooked to date, which indicates the progression of society has not been wholly linear. They noted that the level of the oldest stonework at a few sites appears to be significantly more capable than later stonework. They raised the possibility that there was a retrogression of technology at least once in the history of humankind. Instead of a fruitless discussion of the arguments involved, just suppose that it is a possibility. We might first ask what kind of catastrophe might destroy civilization but not lead to species extinction, not for humans or for any other noticeable species. Is there even a possible phenomena which could wipe out civilization without ending the human species? 

To be able to completely collapse after such an event, totally but not permanently, means that civilization is much more fragile that has been appreciated before. This fragility needs to be understood in terms of the civilization that existed at the time of the catastrophe. That civilization might have taken some different paths that made it more vulnerable that ours is. Or perhaps we underestimate the fragility of our own civilization. What could wipe out our civilization so that only hunter-gatherer tribes were left? Are there any unique events that could do this? 

There are natural catastrophes, like volcanoes, and human catastrophes, like a biowar which targeted food crops. The list of natural catastrophes is quite well-known, as only a few things could affect mankind world-wide. Ice ages could top the list, as there have been several major ice ages, and many more mini ice ages during the non-ice-age intervals. The causes of ice ages are not conclusively determined, but that is of no consequence to the determination of their effects on a civilization. Perhaps one of the most interesting factors is the albedo of ice. Since it is higher that that of uncovered dirt, vegetation, or ocean water, that means that if something happened to increase the fraction of Earth covered by ice, then the amount of heat received by Earth, in total, would decrease, and it would cool down more. This is a positive feedback loop, and could go either way. Orbital variations might be the trigger for this rapid change. The large gas giants affect the orbit of Earth, as an example, and change its eccentricity, and perhaps other parameters. If we look at the collection of possible Earth orbits over the last billion years, we would see there is a distribution, perhaps a bell curve, of the insolation averaged over each year. If the orbit of the Earth was at one end of the distribution of solar energy intercepted, the end where insolation was largest, the climate could snap from ice age to minimal ice in a short time. At the other end of the distribution, it could snap the other way. 'Snap' might mean less than a thousand years or even less than a few hundred. 

Ice melting on such a vast scale changes the sea level depth by something of the order of a hundred meters. If civilization had adopted mostly coastal cities, they would be wiped out in short order. Perhaps this is one candidate for a civilization-terminating catastrophe. Even a lesser amount of melting might drown most cities. Would this end civilization? 

What would happen to a civilization similar to ours if such an event were to happen? Perhaps over a few centuries, most cities would be inundated. People would have to move to higher ground. There is no question, at least on Earth, that there is bare land available for cities, but the benefits of the locations of the previous, now flooded, cities would not be available. These might be ports. A tremendous amount of our trade is by ocean transport. New ports might be available when the seas stop rising, but during the period of continuous rise: no one would be able to build a port which might be flooded in a few more years. So transportation would be seriously affected. 

The costs of building new cities would be very large, and perhaps enough to overwhelm the economy of Earth, or of any comparable civilization of aliens on an exo-planet with a similar ice age phenomena. Would the economy crash, or just degrade enough so that science and technology would be preserved, and the living standard would only decline a moderate amount, not entirely down to hunter-gatherer level. 

Some of this land would have been agricultural, so some food production would be lost. Many countries would be little affected, and others very seriously affected. Would this mean massive migration? Would it mean wars fought over who would control the remaining good land? On top of the possibility of the economy crashing or at least declining significantly, there is the possibility of war, where the holders of good land attempt to stop huge populations of those from inundated lands entering and taking it over. War might not be local, but in many different places, almost at once. If a faltering economy did not cause enough damage, widescale war on top of it might, and here is a possible scenario for a collapse of civilization. 

There are many other questions related to this issue, but they deserve a separate post.