Imagine the scenario of reincarnation. After death of one body, experience reawakens in a different body at the start of a new lifecycle. The facts of the new body constrains what is possible to perceive and to perform and it restrains what influence the re-awakened intelligence to influence the behavior of the body. Just like in the human body there are autonomous systems that are outside of our conscious influence.
Although I am not a believer of reincarnation, this is a nice metaphor for how I see intelligence in biology. Instead of increased complexity generating higher intelligence, it instead empowers the innate intelligence to have influence on the body. The intelligence is always present but it is constrained by varying degrees.
The constraints of what we consider less intelligent life-forms disqualifies them for recognition of their intelligence. This is very practical. This concept of shared comparable intelligence is analogous to the observation that all living beings have DNA. DNA is material and provides an explanation for behavior as well as body structure and function. With a material explanation we do not need a non-material soul-like explanation.
My musings are on the question of are we alone? Are only human able to have human like intelligence. The astronomical study for the search of extra-terrestrial intelligence seeks this answer scientifically.
I think we will never acknowledge such intelligence because we can’t acknowledge intelligence that surrounds us. Some observation of electromagnetic signature may appear to be something that can be the result of an intelligence. But once that observation is studied, I have no doubt that we will find a materialistic explanation. If extra-terrestrials would arrive and allow us to see for ourselves their superior technology, their technology may be so advanced that we would mistake it as natural.
Our biases (or our insecurities) are so strong that about the only intelligence we will accept is something that uses human-like technologies to do human-like thinks with their human-like bodies. We are very clever about finding materialistic explanations for anything that deviates from the model.
We dismiss an animal’s innate ability to figure out how to use its body as instinct. A single cell automatically spins its flagella and it instinctually seeks out food and defends from attackers. A newborn whale calf instinctually understands to not start breathing until it surfaces. A spider instinctually knows not only how to spin a web but to optimally place it for maximum protection and prey-capture potential. Migratory birds instinctually navigate a round world with their use of celestial and magnetic navigation. Behavior is inherited. Behavior is somehow coded in the DNA. No matter how clever, these are not good evidence of intelligence.
We can demand an additional criteria that a creature must be able to modify the external environment. Birds build nests with material they find and modify to fit the nests. Bees do the same thing. Both will use novel materials recently introduced by man, such as plastic bags or caulking. Ants perform massive earthworks to produce elaborate underground networks and sizable hills of excavated debris. These are still behaviors that could come from DNA. They are just more complicated behaviors.
We can further test that in addition to innate behaviors, a creature will not perform some behavior until it is demonstrated in front of him by a more experienced creature (not necessarily the same species). We do not know all of the perceptive faculties of creatures, but we can see examples where behaviors are visually or tactilely demonstrated before the behavior is repeated by the less experienced. This is getting closer. Usually the behaviors are rather basic and may be considered as training (association of a behavior for a specific scenario) as opposed to learning (building a model to use to figure out future scenarios).
Eventually we concede some level of intelligence proportional to larger brain size or brain/body ratios, or how close these approach the human brain. The closest candidates we can identify are still considered to have intelligence that so remote from ours that we don’t acknowledge their eligibility to be our peers.
I decline to insist that our intelligence to be nearly supernatural. I’ll just observe and relate.