Building complex and robust machine may have more ways than just one. To have backups or overlapping systems is one way of doing it, the most stupid and awkward way. Instead of a single engine in a small plane, a more complex large plane may have 4 engines with 2 of them as backups. But is that the nature’s way for using DNA to build complex life? Do we have an extra heart or brain or any organ as pure backups? We don’t. If we don’t do it at the phenotype level, do we do it at the genotype level? Mostly not. Our gene numbers are much smaller than any one had predicted because complexity is not linked to an increase in gene numbers or in back up genes. Nature is smarter and does it by combinations of genes and by inventing novel and complex ways of using the same set of genes. And by giving extra functions to an existing gene. We create music not by inventing more notes, and the ways of using the existing notes are already infinite.
To add back up or overlap system is not really an increase in complexity. A four engine plane and a one engine plane has the same level of complexity as far as the engine is concerned. To have a back up brain, we still need to have a complex brain in the first place. For that to happen, disorder and random mutation must be suppressed. Who can imagine a brain capable of infinite order like mathematics could tolerate a level of disorder/randomness in its building blocks like that of a flu virus or any simple virus like early life forms at the beginning of evolution?
The backup way is also not sound for DNA based lives because, in my thinking, it increases the size of the genome and hence the target size for mutations. The backup copy is not expressed or functional in normal situations and therefore not maintained by natural selection and can easily lose its function due to accumulation of mutations. Thus, it is safe to predict that most paralogs of a gene in a complex organism have unique functions and are not just backups (plenty of data for this). The claim of complex organisms have more backups is simply wishful thinking and not supported by facts. Don’t we have a lot of single mutation diseases in humans?
For both genotypes and phenotypes, nature follows the rule of use it or lose it. Backups may have been invented once but would simply be lost due to disuse. Which is more effective in advancing complexity: to decrease mutations or to use backups? All facts of nature say the first. It is simply a reality that a theory based on that notion explains all facts whereas any theory that ignores it meets with countless contradictions.
There is an extremely common mistake in the evolution field that has infected the lay public. It is to ignore the main pattern and use whatever trivial pattern/facts to suit our theory and to invalidate the main pattern when our theory does not predict it. Given the infinite amount of data/facts of nature, any stupid theory can find some factual support, if the goal is not to account for the major patterns or is not to explain all without contradiction. The advance with time in complexity is the dominant pattern in evolution that is so obvious that it is hardly worth stating. (The best ancient Chinese thinkers from 5000-7000 years ago had always placed man above all else in nature and as equal in status to the creative power of nature namely yang/heaven and yin/earth as written in I-ching, which has been the foundation for the most long lasting civilization as well as the world view of the largest population on Earth. Ancients have much better intuitive sense than moderns simply because their focus is less distracted by trivial things or man-made artifacts, and intuition is the foundation of science.) But since our theory does not predict that, we ignore it and cite trivial cases of randomness to support no direction towards complexity. Or we use trivial and much less common cases of complexity loss like loss of limbs in snakes as evidence for no direction towards higher complexity. Or we cite abundant cases of no change in complexity during microevolution. But all these merely indicate that in addition to complexity increase, there is also another trend for stability or no change. One cannot use a single mechanism to explain two opposite major trends, which is what we are doing.
We ignore the order/beauty/complexity of our big brain, and cite examples of imagined imperfections in some organs as evidence for the imperfections of nature or evolution. We ignore the general perfection of the human body and cite examples of rare diseases to fault the power of nature/evolution. In every case, the main pattern says that nature/evolution is all good, order, and beauty. The existence of disorder, randomness, and ugliness are all trivial and minor patterns. It is simply nonsensical to focus on the minor patterns and to turn blind to the main patterns. We should not explain the trivial at the expanse of the main but that has become a habitual behavior to most followers of evolution, another simple indication that we are not on the right path in understanding the main pattern.