.... So our conscious brains are always involved. They just get so good at it that it's relegated to the background and we don't notice it. So far I have posed several challenges to this hypothesis. I think it remains restricted to autonomic reflex actions and the much slower glandular functions, all of which are pre-programmed and require no conscious thought in the first place.
I noted in my post that the "complex behaviors" I mentioned were not normally called "complex behaviors" and agree that they (and hundreds of others) are called by other names, but they still are "complex behaviors" even so, just as a rose is a rose by any other name.
I also agree the brain plays a significant role in most of them, although some are just reflex arcs that close at the spinal cord -i.e. connect the stimulus to response produced "complex behaviors" (such as the leg jerk with knee tapped)
Most of the brain’s activity has nothing to do with conscious thought yet often produces "complex behaviors." For example, by the brain’s processing of the slight temporal difference* between sudden onset sound waves arriving at the two ears your head will turn towards the sound source without any conscious thought to do so. We can call this a reflex, but it still is a "complex behavior." One can argue the boundary between “reflex” and instinctual behaviors and this example is problematic as present in new borns (but could have been learned in the womb as the mother did turn towards these sounds). None the less, these are all "complex behaviors."
My point is that in many cases, if not all, brain processes determine our conscious behavior WITH NO CONSCIOUS ACTIVITY. For example, it is known that simple decisions are made by the brain up to several seconds and in all cases studied, at least a significant fraction of a second, before we are informed consciously of what has been decided in a binary choice decision.
The early studies demonstrating this used electrodes contacting the exposed brain and the subject watched a faster than normal sweep second hand of a clock. And when he decided (not his brain, but his “conscious choice”) he noted where the sweep second hand was and seconds later reported the position. The doctor, monitoring the brain’s EEG signal knew what the choice would be up to a second earlier than the subject consciously did.
With modern non-invasive technology the recorded signals have shown that the brain made the choice even a few seconds (in some cases) before the subject was aware of "making it." (I.e. had the illusion that he did consciously make the choice.) Thus much of our “conscious behavior” appears to be determined unconsciously by the brain and the conscious "we" is the last to know, but we have the illusion that we “decided.”
Thus with these facts, there is very little difference between "complex behaviors" we have mentioned and given different names, in our ignorant belief that they were fundamentally different. The main difference between them is that “conscious behaviors” are the “complex behaviors” which the brain has made one conscious of. I will however agree that some “conscious behaviors” such a solving an algebraic equation may have essentially no “complex behaviors” of which we are not conscious; however much of routine, natural behavior that appears to be a “conscious behaviors” may just be an illusion of a separate conscious process or decision. This obviously gets deeply in to the question of the existence or not of “free will.”
For many years I thought that too must be an illusion as every behavior is just the end result of discharges in the body’s neural network, especially the brain part of it. The laws of physics, especially diffusion of neuro-transmitters across synaptic clefs and the diffusion of Na ions into the nerve axons to propagate the nerve’s impulse down the axon, determine the firing of each nerve. How could there be “free will" with all this neural activity controlled by the laws of physics?
I have discussed how free will might be consistent with the laws of physics in other posts but continuing here is too far off thread.
SUMMARY of my view on the thread’s question:
“complicated instincts” are not coded anywhere in the DNA. The DNA codes for molecular structures, like proteins. These 3D structures form complexes which further interact to perform functions and a viable body. What it does is a result of these structures and the experiences that body structure (brain included of course) has had. Crudely put: Because of their DNA specified structures, birds fly and snakes crawl, etc.
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* Actually it is much more complex than this as even with only one ear one can crudely locate a sound source. - The sound waves bounce off the external ear also and how these weaker reflected signals combine depends on the locations of the sound source. You cannot even become consciously aware of the information the brain is using o locate the source. Like many other brain process, it is not something you consciously learned, like how to ride a bike, that later became automated. The brain is very pragmatic - it only tells your consciousness a very tiny fraction of what it is doing.