Friday, September 14, 2018

Latitude, Seasonality and Evolution

When we are scanning planets for signs of life, there are levels of priorities based on what attributes the planet has – some planets are more likely to harbor life, as far as we know, than others, and therefore the largest effort should be put into extracting information from these planets.

These parameters are mostly very obvious. We don't want one that is too hot or too cold, as life is an organic process and its molecules are destroyed by heat and inactivated by cold. We don't want one that is too big or too small, as the big ones have to be gas giants as they can hold onto their hydrogen, and the little ones can't hold onto any atmosphere at all. Earthlings think having a small atmosphere is a requirement for life, and it probably is a requirement for the origination of life. An advanced alien civilization might find living on an airless planet not very difficult.

There are two planetary parameters in play here. One is rotation rate and the other is axial tilt. If they are both zero, there is no seasonality. Every minute is the same, provided the ellipticity of the orbit is also small. Unless the atmosphere had some type of difficult-to-imagine instability, then the weather would be the same from one minute to the next and one year to the next as well. It would be possible to define sidereal months, but they would be inconsequential. Nothing would ever change. The assumptions in this extreme case include no moon of significant mass.

Rotation rate goes to zero from the effects of solar tidal forces on the planet. The moon has suffered this and so have other moons in our solar system. No planets have, but Mercury comes close, with a 3:2 phase locking. Venus also has a very low rotation rate. An alien planet with this situation would place life on the planet in a strange situation: nothing every changes about the environment.

This is a different type of fitness test than was present on Earth. There shouldn't be variation in the winds, which would be driven by constant convection forces. Things are about as constant as they can possibly be, and life on such a planet would evolve to a very stable arrangement as well. On a planet such as this, latitude certainly plays a role as it does on every planet, but here longitude is like a variation of latitude. A rotating planet averages over longitude, so that only latitude makes a difference, but on a non-rotator, walking around the equator is very similar to walking to the north pole. There are simply circles of constant illumination, dependent on the angle the sun makes. It keeps the same angle and same position in the sky perpetually. The substellar point would likely be the hottest, and once one passed to the dark side, everything would be cold, except for heating done by winds and the ground.

Winds would likely flow inward on the surface toward the substellar point, driven by the heating of the atmosphere there. That means the flow of air at upper altitudes would be away from the substellar point, and where it would descend is somewhat indeterminate. Likely, descent would be in the circular band near the perimeter where the star is just on the horizon, although it could be a bit inside this. The atmosphere would be too thin to support the toroidal flows that are seen on our solar system's larger planets.

With no tectonics going on, as this needs to be driven by rotation interacting with tidal forces, if there is water, it would be in a circular ring. If the planet were hot enough, no surface water would exist at the substellar point, but as one moved away, there would be a place where water could exist, and perhaps it would create a tremendous moat. On the other side of the moat might be ice, which could continue onto the dark side.

Evolution takes place in a locality, as a huge gene pool takes too long to modify genes by fitness testing. So, in each radial band, circumscribing the substellar point, there would be optimized life forms. Each life form must have some form of mobility, although it might be quite different than here on Earth. With a constant surface wind blowing away from the substellar point, wind-blown seeds would only move outward, and reseeding at the location where a plant was already rooted would not happen. Thus, heavy seeds, such as in a fruit, would be likely in all the various bands.

Evolution likes to migrate, however, so plants would likely have something like rhizomes to move inward toward the substellar point, up to the ring where there is no longer any rain. Animals have no such constraints and could move freely toward and away from the substellar point, as their capabilities to compete in adjacent bands developed.

The other two possibilities, bring closer in or farther out from the star, would provide different bull's eye patterns. Too far out and there would be ice everywhere, with only snow falling near the substellar point and nothing beyond a certain radius. Too far in and there would be no liquid water on the lighted side, and perhaps some chemotropes living in the dark but wet band just past the light boundary.

Whether or not life could originate on such a planet depends on how it originates. If the theory expounded in this blog, the organic oceans theory, where life only could originate in an early Earth-like setting, would rule out life originating on a phase-locked planet, unless some very unusual planetary movements had taken place. Maybe if there was a moon, but it eventually drifted so far out that it could detach from its planet, and then the planet became phase-locked, something might be possible. If some other theory is the correct one, such as the sea-vent concept, this planet would would be a loser, as without continents and oceans, there would be no sea vents. Perhaps life would find a completely unique way of originating on such a planet however, but out preoccupation with life here on Earth inhibits our realizing how it might happen. 

Sunday, September 9, 2018

The Convergence of Quality in Genetics


Consider an animal. It has genes which came from the gene pool for its species. If gene selection was random, looking at animals of that species you would see some which are superior in appearance, others superior in physical ability or agility, others superior in perception or mental abilities, others superior in strength, and so on. The best genes for one attribute set would be in some subset of animals of this species; the best genes for another attribute set would in another subset, and so on. The number of those who are superior in both attribute set one and attribute set two would be small, just the product of the fraction of these two qualities compared to the whole set of animals in that species. The number of those who are superior in three attributes would be multiplicatively smaller still. 

That’s not the way it goes. There is a correlation between having superior genes for one attribute set and for another, so the numbers are higher that just the product of the fraction in each attribute set alone. Just to give a numerical example, suppose the animals who are the fastest runners, moving individually, are 10%, and the animals who have the sharpest perception skills are likewise 10%. The numbers of course depend on the thresholds set for superiority. If everything were random, there would be 1% who are both the fastest runners and the most perceptive. But there are more of them, maybe 2% or 5%. Why does this happen?

Consider three types of animals. One, a species where individuals are loners. Two, a species that lives in herds and are prey for other species. Three, a species that hunts in groups.

In the first species, during mate selection, males of the species compete for desirable females. The competition in both males and females will go preferentially to those who are superior in one or more attributes. Who gets the superior spouses? The superior animals of the other gender, as they win the competition more frequently. Thus we have mating of superior animals, with superiority in different attribute sets, together, and some of the offspring will be superior in both parents’ categories. These offspring will survive to the age of mating with higher probability, and the correlation starts to increase. Over many generations, it will increase to a level controlled by the natural randomness of life and surely multiple other factors. But this is a possible mechanism by which the correlation can happen.

This mechanism works with all species, not just loners. Whenever there is a bi-gender competition for mates, the correlation will creep in.

The same correlation will occur in the gene pool if there is a correlation between two attribute sets in necessary activities. For example, if it is easier for some animal in a particular species to gather food if they are both better at reaching it, from length of limbs or something else, and also better at spotting it, from more acute perception, in a synergistic way, then this correlation will eventually translate over into a correlation in the gene pool. This does not only relate to food gathering, but also hunting, if the species does that, in avoiding predators, if it is subject to this problem, in surviving temperature extremes, or in finding the way back to its den, or other activities which contribute to the survivability and eventually reproduction rate of an individual animal.

For herd animals, where there are some special competitive actions, such as rights to the best food or to be protected by the largest animals of the herd, or to be nurtured by non-parental animals as a young animal, or to be the leader in any stampede, or anything else which might promote reproduction rate, then the same synergistic correlation in activities will translate into a correlation in genetic superiority in more than one attribute set. The competition between herd animals for these positions of priority is based on multiple attributes, and synergism is quite reasonable to expect. 

For predator groups, animals which live in groups and where the adults mostly hunt together, there is much the same group leader or top animal hierarchy effects which occur here. The attributes would be quite different, such as jaw strength, ability to intimidate, ability to inspire others to follow, ferociousness, and others, but those gene sets which lead to each of these might serve to add to the probability an individual will reach top status in the group.

In an alien species which is becoming intelligent, there is no reason to think that these two effects: mate selection and synergism in necessary activities, would be any less of an influence in producing individuals who excel in more than one attribute set, perhaps leading to an accumulation of superior genes in a small fraction of the population. Healthiness is an attribute set that has not been mentioned before, but it plays a large role in reproduction rate. So also might food tolerance, or the ability to digest multiple sources of nutrition. Many others certainly exist.

The downstream impact of this, as the alien species begins to live in fixed locations and develop a civilization, is that there would be a tendency for some class distinctions to arise, probably hereditary as well. The pathway exists in any alien civilization which has the wherewithal to develop tool use and start its way up the ladder of technology to a situation where there are large differences among individuals in many attributes, but in a correlated way. Thus, some nobility or upper caste or something similar is likely to exist during a phase of the species’ technology development.

This translates into a problem. Individuals who are superior in many ways, and are so since birth, and because of it have enjoyed more fruits of the civilization than others, would be loath to relinquish their position at the top. Thus, this group of powerful individuals might seek to block the spread of genetic wealth down to the remainder of the society. Is it possible that they could seek to freeze society in the state they find it in?

This would be a worry for any prediction that a civilization eventually reaches asymptotic technology, except for the fact that civilizations are not stable at intermediate levels. Stasis eventually leads to decline and then a turn-around and another climb, each time higher. Eventually the civilization should pass through the genetic grand transformation, and after that, can easily stabilize, and then proceed on to star travel, if such things are possible and within their grasp, relative to the resources of their solar system.

Sunday, September 2, 2018

Dark Planets


What can happen concerning life on a planet without any sunlight? A planet at a favorable radius from its star, but with an atmosphere continually and completely covered with clouds is an easily concocted example. Earth had life long before life could use solar photons for energy, either directly or indirectly via feasting on a food chain starting with solar photons. It is believed that early Earth life was powered by chemical energy.

Chemistry can provide plenty of energy. To give our dark planet the best chance of making something impressive without photons, suppose that it has an abundance of chemical energy. Consider an ocean on the dark planet first. Suppose there are continuous volcanic events somewhere, and the ocean circulates the chemical products everywhere throughout the connected seas. Maybe there is a basalt flood going on somewhere, dumping something like methane and other alkanes into the water, along with ammonia, ferrous iron, and other edible tidbits. Far away from that, some chemotrophs are busy oxidizing these chemicals. It is like a whole ocean as rich as one of Earth’s undersea vents.

There might be a variable density of these creatures, with more of them nearer the principal sources of chemical energy, but not too close because the water temperature is higher there. There can be a wide variety of life in such conditions, as demonstrated by the various microbes and animals which inhabit sea vents. Our life forms are limited by the evolution that can happen in the duration of a sea vent, but if we imagine the dark planet to have recurring basalt flooding, maybe multiple at a time, perhaps caused by asteroid impacts, then evolution might go on for billions of years in a chemical energy-rich environment, leading to a variety of creatures far beyond what we see at a sea vent.

There is a question here on Earth as to whether the organic chemicals forming cells in the creatures inhabiting the vicinity of a sea vent have been contaminated or worse, contributed to by photic life forms living in the upper layers of the seas. This is not a question for the dark planet, as it could not happen there without any sunlight, but more pointedly, what can evolve in a phototroph can evolve in a chemotroph, although maybe not as speedily. DNA mutation is simply a change in DNA, caused by one mutagen or another or just by accidental errors in DNA copying. Where it happens is largely immaterial.

Consider the atmosphere. If the dark planet has continuously producing basalt floods, the atmosphere may also be full of chemical energy sources, such as the smaller alkanes and ammonia. Is it conceivable that an organism could emerge from the ocean and live on land on the dark planet? Breathing would be the same as eating, and the organism would not resemble anything easily imaginable from Earth’s examples.

One advantage that life had on Earth was that photons arriving on the land surface are more abundant than those arriving underwater, as water absorbs some of them. This means it can be an evolutionary advantage for a plant to live closer and closer to the surface, and eventually migrate to living in the shallows and then on land. A DP-plant would have a corresponding disadvantage, as the atmosphere, being a gas, can hold much less of the energetic chemicals. This does not mean that there would be no land life, but that it probably would not have the diversity that proximity to a solar energy source provides here on Earth.

On Earth, we have a nice clean division between plants and animals, as plants are almost uniformly photosynthetic while animals live on plants, or on other animals. On the dark planet, there might be a similar division, between DP-plants, which live on chemical energy in the oceans or in the atmosphere, and DP-animals, which consume DP-plants. Earth plants typically maximize the absorption of sunlight, by having such things as leaves. Sunlight is absorbed by a surface. Chemicals in a fluid have to be absorbed by maximizing the flow of the medium through or past an absorbing surface. One possible arrangement might be a porous DP-plant, though which the ocean continually flows. This would work if the DP-plant were fastened to the seafloor near a constant or almost constant flow of seawater. Any DP-plant which was free-floating would have to have a mechanism for circulating the ocean water past its chemical digestion tract, much like many Earth sea creatures do who dine on microscopic organisms floating in the water.

Without sunlight, vision might not evolve, neither in oceanic life nor in any creatures which manage to live on the land surface. Senses would be restricted to smell, taste, touch, and vibration. Perhaps some will evolve electrical discharge capability, initially for defense or predation, but perhaps later for communication. Earth has evolved creatures with electrical discharge ability, but perhaps none which can reliably detect a discharge. This does not mean that evolution is not capable of it, but instead that there are so many excellent competing senses possible here that it did not emerge.

How far can evolution take life on a dark planet? Suppose that such a planet were formed early in the history of the galaxy, so that life has had maybe ten or eleven billion years to evolve there. Could there be animals which live in packs, communicating with vibrations or electrical signals? These are all short range, and low frequency acoustics might serve for long-range communications. Another sense possible is echolocation, which has only evolved in the sea in mammals on Earth, but could easily be supposed to evolve in whatever DP-animals arise.

There is a stopping point, however, in the march of evolution on a dark planet. One problem is tool-use, and an example is the specific first tool used by primates, fire. There is nothing equivalent in an ocean. Nor are there advantages to developing the limbs needed to use tools, such as a primate’s hands. Thus, evolution can go a very long distance, but not in the direction of intelligence.

If there was such a planet as our dark planet, teeming with life but no intelligence, would it be detectable? With a cloud cover, no evidence would be visible to even a huge telescope. No oxygen is present, which is considered, perhaps prematurely, as the indicator of life. Such a dark planet might be passed over, even by a nearby alien civilization who were hunting for other planets with life. 

Does this make any difference? Could an alien civilization make any use of a dark planet such as the one we have been postulating? If the energy source is continuous basalt flooding caused by asteroid impact, then the question would be, could there be any regions present there which could be visited, even temporarily by an alien landing party? If the basalt flooding were underwater, in a deep part of the ocean, possibly the land surface might be tolerable, even if the atmosphere was extremely toxic. It is an extremely interesting thought exercise to see if there was any reason that an alien civilization would want to visit such a planet, or to establish some sort of colony there. Perhaps this blog will return to the topic to suggest something relevant.