Happiness is a strange thing, and it can sometimes be elusive, even though we often try to make choices to maximize it. One of the downsides of being as conscious as we are is that we are often aware that we are in pursuit of happiness. Yet sometimes we focus on the wrong goals. Keeping up with the Joneses and accruing vast wealth might not make you happy, but it is what we tend to focus on. Perhaps consciousness is not always as wonderful as we might think.
Plants and fungi are not conscious. They have no brain or equivalent organ to feel experiences of the world around them. They do not produce even rudimentary brainwaves. Although they are not sentient, they can still respond to environmental cues, growing towards the light and extending roots downwards, but these processes require no decisions to be made. Developments of particular parts of a plant or mushroom are towards a cue, be it light, gravity or water, that rudimentary sensing cells detect. These sensing cells do not link to neurons in a brain to be interpreted.
Unicellular organisms also lack the ability to be conscious, but they too can respond to environmental cues, using specialist organelles called cilia to move through their environment towards or away from useful and harmful chemical stimuli. These single-celled organisms can detect chemical cues in their environment, and as molecules that carry these cues bind to proteins on the surface of the cell, they can respond by moving towards or away from the cue.
Brains are the domain of animals, but not all animals have them. Adult sponges do not have brains, nor any form of nervous system. In some species of sponge, juvenile larvae do have simple brains. The larvae use these to move and to find somewhere to settle. Once a suitable piece of real estate is identified, the larva settles in a place to call home and begins to develop into an adult. As it does so, it digests its brain, as it is no longer useful. Several other sedentary animals, such as mussels and oysters, also lack brains. Those few species of animals that do not move and have a brain tend to have very simple ones. The ability to move seems to have been the evolutionary driver of developing a brain.
Why would the ability of multicellular animals to move drive the development of a brain? The evolution of muscles permits movement, which is the ability to, temporarily at least, resist the forces of gravity and electromagnetism. A rock, or indeed an adult sponge, is unable to resist these forces, but every time you walk, you use energy to resist gravity, lifting your feet and placing them in a new position. You also move through air, resisting the drag created by the electromagnetic force as you move. Being able to move opens up the way for choice and the option of making decisions: should I go over there, or stay here? The evolution of movement makes free will, and consciousness, a possibility, even if not a necessity. Complex mobile animals have choices, and evolution has produced complex brains, and presumably consciousness, to help organisms make the best possible choices. Swimming bacteria and archaea can move, and by this argument could have free will, but no within-cell brain organelle has ever evolved to allow decision-making.
Moving allows animals to escape from harmful environments, but to do this they need to sense harm. Even quite simple animals appear to be able to register pleasure and pain. Houseflies modify their behaviour after experiencing an injury, although it is unclear whether they feel pain in quite the same way as us. Nonetheless, if an animal has a nervous system such that they can transmit signatures from sensory organs to the brain and back to muscles, and act in response, it suggests that the sensation of pain is a characteristic that evolved at around the time the first mobile animals appeared on the tree of life. The first wisps of free will likely evolved with the ability to make directed movements. Pain is an effective way of telling an animal to act, and to do so quickly.
There is a terrible condition in humans called congenital analgesia that, fortunately, is extremely rare. Those who suffer from it cannot feel pain. The condition is caused by genetic mutations that prevent some types of neurons communicating effectively by impacting the flow of ions across the cell membranes that form synapses. Signals cannot be sent through the body’s network of neurons in the usual way. Congenital analgesia is extremely dangerous, as individuals are frequently injuring themselves as they do not respond to harmful stimuli, and sufferers often die young from accidents. Registering pain is an important part of being an animal, and that is why fruit flies, shrimps, fish and snakes are all able to do it, even if they don’t feel pain in exactly the same way as we do.
A key challenge in the science of consciousness is working out exactly what it is that different animals experience. How widespread is consciousness, and how does its degree differ between different species? In the last few decades, a growing number of scientists have concluded that even quite simple animals, including invertebrates such as shrimp, lobsters and octopus, can experience pain and probably other emotions similar to pleasure. They do not think that all these animals experience pain and pleasure in identical ways, and exactly what pain means to a crab, or a lamprey, is yet to be worked out. We do not yet know what it feels like to be a bat, rat or cat. Nonetheless, the ability to experience pain is a very ancient trait, it is probably the first emotion that any animal experienced, with higher degrees of consciousness, perhaps even complex thought, evolving from the ability of early animals to experience pain. When any individual experiences pain, regardless of the species, it will not be pleasant, and this means we do need to re-evaluate how we treat species like crayfish, lobsters, octopus, chickens, pigs and cows.
Scientists have compared the structures of brains in animals across the tree of life, and this has helped them work out how brains, and to a lesser extent consciousness, have evolved. The simplest brains consist of only a small number of neurons, with each looking the same. More complex brains, including ours, consist of lots of different types of neurons that are linked together in all sorts of different configurations. Different types of neurons in different areas of the brain can differ in shape and in the number of synapses they form, even though each neuron contains the same structures such as an axon and dendrites.
Brains evolved and became more complex by increasing the number of neurons, by diversifying their shapes, and by playing with the way they are connected. As we move through the tree of life from the first animals to you and me, we see that brains get more complex, with new areas being built on top of existing areas. Evolution has tended to add on new sections as brains have become more complex. Evolution is like a builder, adding on extensions when a new function provides a fitness advantage. Mammals developed the neocortex, something that is not found in other animals, and humans take the size of the neocortex to an extreme. During development, we grow lots and lots of neurons in the neocortex to a greater extent than most other mammals do. In contrast, Woofler developed a long nose with lots of cells that can detect smells along with a relatively larger part of the brain that enables him to interpret smells to a much greater extent than humans can. He can read the recent history of a patch of ground through smell in a way we can’t, and this helps him locate prey to hunt. But evolution can shrink areas of the brain too. Some of our ancestors had better sight, hearing and smell than we do, but they could not solve crosswords or sudoku puzzles or master fire. On our branch of the tree of life, our brains have increased in size, but the relative size of different areas has fluctuated over the last hundreds of millions of years. We are at a point where it is beneficial to have a large neocortex, but perhaps as artificial intelligence becomes more human, we will lose the need for such an organ. Perhaps our descendants will return to the trees and lose the ability to speak while artificial intelligence does all the heavy lifting. Predicting the future is beyond this book, but understanding the past is not. We are now at a point in our history where mammals have evolved, and where animals are conscious, but I am yet to discuss how humans came to dominate the planet. That is the topic of the next chapter. Why are there humans?