Why are there only a handful of species on this planet, of which humans are the pinnacle at the moment, that are capable of sentient thought? Humans, dolphins, whales, and that's about it(there may be more, but these are the ones I know of). What if, at some point in history, the brains of humans and those other creatures became intelligent enough to start shaping their own DNA? It seems silly to think humans have thumbs because it's helpful to hold tools with because how would your DNA know about tools or how useful thumbs are for them? What if the brain subconsciously modifies DNA on it's own? It's not that far fetched. The brain is the least understood of our body parts while being the most important, at least for setting us apart from other animals. What if intelligent creatures subconsciously direct their own evolution? Keep in mind that I'm not claiming to have scientific evidence of this. My scientific interests are with physics and astronomy, and biology/genetics are not an area that I have vast knowledge of. It may be that I am completely wrong and this is impossible. But either way, I've been thinking about it recently and came up with this idea.
No, this is totally far fetched. DNA doesn't have to know about tools. If a mutation has benefits that outweigh the cons then it will be selected for due to natural selection.
Specifically in regards to your example of thumbs; it could be postulated that during a time and in a place where there were many trees the creatures that would become apes found themselves advantaged if they happened to be born with a mutation which allowed them to cling to or climb onto trees such that they could avoid predators. As such mutations which created more and more useful thumb-like fingers would be naturally selected into the gene pool that would become humans. This is not necessarily the only reason but as you can see there are evolutionary explanations for thumbs. Even if we did not have an explanation for the evolution of thumbs, there would be no evidence to support your hypothesis that intelligence has made evolutionary decisions in the past.
We understand the mechanisms of evolution very well: selection (of various kinds, natural, sexual) is the most commonly referred to, but we also have drift, gene flow, hybridization, hitchhiking, etc. Directed evolution is a fictional trope of comics and bad scifi. It doesn't even make good sense. Evolution occurs at the population level*: it is defined as allele frequency change of a population over time. It doesn't occur at the individual level. All individuals eventually die. It's how their differential success of survival and reproduction affects the genetic makeup of the population that matters. There is no reasonable mechanism by which the brain can change its own DNA. *This is different from saying that the unit of selection is the gene.
Long range, mutation directed evolution will, or at least could be, partially superseded by direct gene manipulation. It's already being done in the laboratory. Defective, disease producing genes can and will be be repaired. How widespread this becomes within the human population in the future remains to be seen. Genetic repairs within affected gametes would propagate the repair and tend to reduce the defective gene's propagation through the subsequent population. Eventually, the ravaging effects of Alzheimers, Huntington's, Parkinson, and other genetic mutational diseases can theoretically be drastically reduced, both without and/or in spite of evolution. It will boil down to how willing and able humanity will become in submitting its own reproductive activities to institutionalized medical controls. I'm not necessarily advocating such extremes in societal regulatory control. I'm merely saying that the technological potential for realizing such widespread victory over mutation related diseases exists and will continue to become more feasible in the future.
The subconscience would do the contrary. The subconsience is a radar processing the millions of optical, accustical, olfactory and tactile inputs we get every second without bothering conscience. Subconscience in contrary to conscience never sleeps, cannot be hypnotized or drugged. It simply scans the environment for threats, thus helping us to survive. "Evolution" is a partial change of species. Subconscience would do everything to prevent it. It prefers "bad but familiar" to "potentially better but potentially more dangerous". That is why women everytime run into the same violent partner and businessmen into the same bancrupcy. It is subconscience steering them secretly (and ourselves nobody knows in which direction). On the other hand the dogma that genes cannot store memories to my opinion is wrong. Proof: Take European sing birds. They exist since the dinosaurs. And since the dinosaurs they fly to Africa during the European summer and come back in spring. Continents however move. Only slowly but they move. If those birds navigatimg with the help of the earth magnetism always would fly along the same magnetic vector, the first ten thousand generations could correct the error resulting from continental drift optically. For one generation the continent however would have been out of view. Those birds would disappear. The fact that they didn't shows that small correction factors are passed by heredity. That simply means the genes can store memories from our daily experience.
