Origins of Vision-Based Cognition
Development of Vision
The sense of vision developed and evolved in the Cambrian period. Vision is so fundamental to most of us, that it is difficult to conceive that the world was once without vision, and hence without light. Until the Cambrian period, no living thing was able to see the environment. Until there was vision, there was only electromagnetic energy at an almost unlimited number of wavelengths, but there was no light. Light is defined as those wavelengths which can be seen by an animal. Without eyes to sense the electromagnetic wavelengths … there is no such thing as “light”. Light was created during the Cambrian explosion.
The development of vision in the Cambrian period is documented in “In the Blink of an Eye” by Andrew Parker. He discusses how the sense of vision developed very rapidly during the Cambrian period and how it likely drove the evolutionary process because of its immense survival value. The majority of developments in eyes are thought to have occurred over the span of only a few million years.
The evolutionary plausibility of something as complex as an eye is supported by the work of David Plachetzki and Todd Oakley at the University of California at Santa Barbara and by Dan-Erik Nilsson form Lund University in Sweden. Plachetzki and Oakley have described a current animal (hydra) that has no eyes but that can sense light because of light sensitive proteins (opsin) on the outside of their body. Opsin serves as the basis for photopigments that are the initial light sensors used in animal and human vision. This finding that light-sensitive pigments have been found on the skin supports the Nilsson proposal for the evolutionary development of an eye. As a first stage, the opsin proteins form in conjunction with small pits in the skin of the animal. Because of the shadowing that occurs in a pit based upon the direction of the light, crude directional sensitivity is accomplished as shown in the illustration. With further development (shown in the Figure), the opening to the pit becomes very small, effectively creating a pinhole camera with greater directional sensitivity and even some imaging capability. Skin overgrowth creates a cornea (corneal tissue is derived from ectoderm similar to skin) and eventually we have a modern eye. Nilsson evaluates the rate of evolutionary change and determines there is more than enough evolutionary time for this to have occurred.
Proposed evolutionary development of eye
Figure. Proposed evolutionary development of eye. Initially, the shallow depression in skin, which contained photosensitive molecules, was sensitive to the direction of light because of the shadowing that occurred. This progressed to a smaller opening and optical imaging. Picture from Nilsson, Dan-Erik: Department of Zoology, Lund University in Sweden, with permission.
Role of Vision in the Cambrian Explosion
The sense of vision, today as during the Cambrian period, requires considerable neural networks to translate the signals received from opsin-driven nerves into a usable map of the world. Survival also required that the neural signals from the opsin-driven nerves be translated into muscle driven evasive or attack movements. The nervous system that developed around the sense of vision was certainly the most advanced neural network in each of the successful Cambrian animals.
The strategy for evolution is “survival of the fittest”. The importance of vision to survival cannot be over-emphasized. An animal with superior directional sensitivity and/or imaging capabilities will have clear survival advantage in a world in which animals can navigate their environment. Whether to find and locate prey, or to evade being such prey; vision was the primary sense used to guide action of the animal. Parker suggests, with considerable reason, that the evolution of vision was the catalyst for the Cambrian Explosion. Attack behavior based upon the sense of vision also supported development of defensive attributes such as hard exo-skeletons (armor) and camouflage.
During the critical Cambrian period the sense of vision, with its advanced and complex neurological network, was at the center of the Darwinian struggle for survival. Vision was a principal driver of evolution.
“World”, “Self”, and “Group”
For each individual animal, vision provided an internal map of the external world. At first vision was quite crude and provided only information about the direction of light. Even this, however, would be extremely useful information compared to not having it at all. As vision developed, the animal became able to identify images in the world around it. Prior to the existence of vision, only the senses of touch or taste/smell gave information about a “world” external to the animal.
The concept of the external “world” is encoded in the neurology that perceives vision
Vision provided the animal with a view and map of the external world. As animals developed awareness of an external world, it necessarily invoked the concept that there was something inside the animal that was viewing the world. Self-identity of the organism was necessarily concurrent with the sense of vision and view of the external world. The animal navigated and interacted with the world using vision as its primary guidance and neurological system; the organism had to have some sort of self-awareness as it interacted with the visual world around it.
The concept of “self” is strongly encoded in the sense of vision and the neurology that developed to interpret vision.
With vision, the animal observed other things, some which were fixed in the environment such as rocks and plants, and some which moved in the environment and served as either food or sources of danger. All of these required some sort of muscular response or action – if only to avoid collision. Navigation within the observed environment required an additional skill: knowledge of the animal’s body orientation within the environment with respect to gravity. This was accomplished through the use of a statocyst, which likely evolved as a small in-pouch of skin with some sediment that stimulated different areas of the pouch depending upon gravitational orientation. Vision, along with orientation information from a statocyst, enabled navigation within the world. Very importantly, survival of “self” was the primary objective of vision and its associated neurology as each animal strove to survive.
With vision, the animal also observed that some of the other moving things in the environment were like its self and did not serve as either food or sources of danger. In fact…..quite the opposite. There were survival advantages to being with the “group” of like organisms. There was safety in numbers and numerous ways in which groups of like animals could be more successful at survival in the hostile environment. There was one other strong concept that developed in close association to the sense of vision: reproduction. Sexual reproduction developed and flourished in the Cambrian period. Vision served the animal by identifying sexual partners – something critical to survival of the species.
Therefore, both the concepts of “self” and the concept of “group”, shown in the diagram below, developed around the sense of vision very early in evolution. Survival was the objective.
Figure. The Cambrian-era cognitive concepts based upon the sense of vision, serving as the evolutionary foundation for our vision-based right brain.
In summary, during the explosive development of life in the Cambrian period, vision developed rapidly and played a major role in survival and evolutionary development. The sense of vision was fundamental to the concepts of “self” and “group”, and it was also fundamental to reproduction and survival – the main objectives of the animal. These fundamental concepts or drives are associated with the cognitive skills that have developed from the sense of vision. They remain a major part of Homo sapiens today (to be discussed later).
The sense of vision goes very deep into the evolutionary depths of life and into the genetic code of life. We share the sense of vision and many of the vision-derived cognitive skills with animals.
Development of cognition
From an evolutionary perspective, when and how did a mind develop? Somewhere between single celled animals and Homo sapiens a mind developed. Our mind, consciousness, and cognitive skills reside in our brain. The brain is an accumulation of neural tissue located in the forefront or head of the animal. Such anterior accumulation of neural tissue first occurred in the Cambrian animals. It is unlikely that animals prior to the Cambrian period had any sort of mind or awareness.
The first step towards developing a mind was probably a sense of awareness. As discussed earlier, vision gave the animal an awareness of “self” as distinct from “world”. This would have developed gradually. In the earliest stages of vision development, when vision was really only crude detection of the direction of light, the neural signals regarding light direction may have directly guided muscle movement towards the light without any involvement of central neural processing or accompanying perception. However, central neural processing certainly became necessary when the eye became capable of discerning many different directions and imaging became possible. Image processing required sophisticated neural circuitry.
Vision required more advanced neural processing for the animal than any other body function or ability. The strong survival value of vision provided the drive for better image detection and the neural capabilities to support it. The most advanced neurological circuits in the neural bulb at the head of Cambrian animals was most likely consumed with vision. The budding brain, based upon the sense of vision, was tasked with survival and was aware of “self” and “world”. This was likely the beginning of awareness and mind.
Survival depended not just on seeing the world, but reacting to the image of the world. This required assessments of the patterns of light and darkness such as size, movement, direction, and other detail. Vision involves assessment of images or pictures. This requires parallel processing of information; and the neural networks that interpret vision developed around that capability. The animal’s neural interpretation of the visual world would have affected survival and impacted the entire organism. The neural interpretation would signal “safe” or “danger” to the animal. It would also signal “group” or “other”. As vision and vision processing developed, so also did awareness of “self”, “group” and “world”. These basic recognition patterns were developed very early in evolution of the mind and remain as fundamental concepts supported by our right brain. The growing skills at assessing vision evolved into cognition that is based on vision. Such cognition includes feelings, emotions, instincts, creativity and understanding.
Cambrian awareness of the world was based upon vision and the neurology that evolved to support it. The minds of animals largely developed around neurology to support the sense of vision.