The issue of complexity
Sources of complexity: the big bang and evolution
There are two major things that resulted in the “world” (the totality of everything that exists) being surprisingly complex. The first thing is closely related to the big bang. The universe turned out to be very structured immediately after the big bang, with different levels of material density, radiation, temperature etc. This caused the formation of stars, galaxies and solid material. From then on entropy has increased continuously for almost 14 billion years, but still the world looks pretty structured.
The second thing was the biological evolution on our planet that is responsible for almost every form of complexity that we experience in our daily life. While the general structure of the universe came from something like an initial condition, evolution was a long process during which complexity increased almost all the time. Most people find the latter amazing. And many don’t believe it could have happened just like that. It is definitely a fact that demands an explanation.
The whole issue is tricky not only because complexity is difficult to define, but also because the question how to explain the existence of such a vast amount of complexity can’t be separated from the heated debates between evangelical Christians and naturalists. Evangelicals claim that evolution would have been impossible without god, while naturalists claim that evolution is a natural process. Many naturalists also claim that evolution will happen almost inevitably whenever the environmental conditions don’t prevent it straight away.
These are the major questions about complexity:
How can we define complexity?
While everybody has an intuitive understanding of complexity the formal definitions are rather abstract. Basically the amount of complexity can be seen as the minimum amount of information needed to fully describe something. The thermodynamic approach is to ask how frequently something will appear at random. Complexity then is the logarithm of the reciprocal of the a priory probability for this random emergence.
Read more about complexity defined here.
Why do evangelicals want to prove evolution wrong?
Evangelicals and creationists claim that evolution can’t have happened the way it is being told by modern evolution theory. This claim is mainly a political statement. Evangelicals want to prove evolution wrong, not out of scientific interest but in order to push their political agenda and to heave creationism taught in science classes.
Read more about creationism here.
What if evolution would indeed violate the second law?
If evolution should turn out to violate the second law of thermodynamics, this wouldn't prove much in terms of god's guidance. Even if an unguided evolution would be extremely unlikely a priori, so that only very few cases exist at all where evolution managed to create an intelligent species, then due to the so-called anthropic bias these intelligent species will observe their own habitats only, while the myriads of solar systems without intelligent life will stay unobserved.
Read more about the anthropic bias here.
What about the so-called “universal probability bound”?
In a finite universe with discrete time there is only a limited amount of things that can happen anywhere ever. If the probability of an event like evolution on our planet would be not only very low but so ridiculously low, that is some magnitudes smaller than the reciprocal of the number of events happening anywhere ever, this event can be regarded as virtually impossible. Such a “too low” probability is called a universal probability bound. However such a limit does not exist as long as we don't know how big the universe actually is and whether it is finite at all. Therefore the idea that evolution not only violates the principles of statistical physics (making evolution uncommon but not necessarily unlikely) but violates them in a very extreme way is still perfectly compatible with a purely naturalistic world view, regardless how small the a priori probability for evolution might be.
Read more about probability bounds here.
So does evolution violate the second law after all?
Our whole solar system can be regarded as close enough to a closed system, unlike the planet earth alone. If we talk about statistical physics in general and not only about thermodynamics, then different types of high or low entropy have to be distinguished. Low thermodynamic entropy in our solar system is one kind of effect, low entropy in terms of genetic information is an entirely different one. The critical point is that the existence of one effect as such doesn’t automatically make the occurrence of a different type of effect any more likely. Such a correlation would have to be proven separately for that particular case, as it does not follow from applying statistical physics in general. Our solar system went from high entropy to low entropy in terms of genetic and biological information. This is so far an unusual exception within statistical physics unless some other explanation would be found.
Read more about statistical physics here.
What evidence would prove evolution to be nonetheless common?
Discovery of extraterrestrial life, successful simulation of the increase of complexity in laboratory experiments or the tree of life having upwards oriented branches would be evidence for evolution to be common. With any evidence of that sort missing an uncommon evolution is the most credible assumption.
Read more about common evolution here.
What are the consequences of evolution being very uncommon?
If evolution is an extremely uncommon process, which is reasonable to believe, we will never fully understand the human mind, we are most likely not part of a universal simulation, we will fail to simulate the increase of complexity in evolution, we will never meet our next door alien neighbors, complexity of biological life will decrease fast from now, and the branches of the biological tree of life are in fact flat. But the Darwinian theory of evolution together with most of their concepts still holds and no god is required in the context of scientific reasoning.
Read more about uncommon evolution here.