Good science is comparative. Because horses are hoofed herd animals, they have much in common with cattle and deer. Because they are mammals, they have much in common with raccoons and dogs. They are animals and so have much in common with octopus, birds and fish. Our lineage defines our form, but our behaviors can often be traced far back on the family tree. When we find common behaviors across different twigs of the family tree, we can know that we have found an ancient behavior and can often learn about one species by looking carefully at another. When a sandpiper, baby raccoon, or horse threaten, they all bend down, assume a snowplow position with their heads, and move forward. Surely animals have been threatening each other for eons. New species do not bother to invent new behaviors when the old ones work perfectly well.
Understanding the evolution of consciousness will not come from looking for intelligent behavior in other animals, but rather from understanding the fundamental mechanisms that support subjective awareness and selective attention, which we now know insects have.
Consciousness is a summary, produced by the non-conscious brain, and tossed up for us to view. Consciousness requires extra brain work to produce. The hard parts of thinking all happen below the level of consciousness, and we must make an effort to tap what is going on. The thinking that our brain does below consciousness, or before we are consciously aware of what it is doing, is the important part. All animals have the general capabilities of that most important part, and whether they are conscious or not doesn’t much matter.