Foundations of Animal Consciousness

When a banana harvesting machine detects and grabs a banana, there is nothing it’s like to be that machine. The machine does not have a point of view or a stream of consciousness. But when a human or monkey looks a banana, there is something it’s like for us to see it. Qualities of the fruit’s shape, size, and color manifest in our stream of consciousness. If we grasp the object, we can feel its texture and firmness. And if we bite into the banana, we can taste its sweetness. Most agree that primates are not the only kinds of creatures that have experiences like taste, smell, sight, touch, sounds, pleasure and pain. But it can be difficult to sort out which other creatures do, as well as the qualities that decorate their inner worlds. Do worms have any experiences or are they like the banana harvesting machine? Do wasps experience pain when sprayed with Raid? Do fish experience fear or sadness? And what should we say about octopuses?  

You might ask, “how we could possibly know what’s going on inside another creature’s head?!” There’s no way to peek inside to see their thoughts or emotions. What if all nonhuman creatures are mindless machines? The 17^th century philosopher Rene Descartes thought that animals were complex automata that God designed for us to use, programmed to react to stimuli without ever feeling or thinking anything. Humans are special, says Descartes, because we are immaterial souls created by God to exercise free control over our bodies. While we can’t definitively say he is wrong, Descartes’s views about animal minds are now extremely controversial, even among theists. But why exactly do most philosophers today reject Descartes’s views about animals? Part of the story is that we’ve learned a lot more about animal behavior, the brain, and the evolution of life on Earth. The other part of the story involves reasoning from this newly acquired knowledge to the existence of animal minds. Conceptual tools like analogical inferences and inferences to the best explanation can be used to build bridges between our observations of the world and our theories. Before judging the reasons philosophers have for thinking some animals have minds, it’s useful to first review the reasons for thinking that other people have minds.

How do you know that you aren’t alone in this world? It’s possible that all other humans that you interact with are like the banana harvesting machine but behave like they have minds. How could that be? Perhaps you are in a perfect computer simulation and those around you are all mindless NPCs. Or maybe your mind has just been spontaneously created by a freak natural accident with false memories of a past and you’re currently dreaming all of this up. It’s impossible to conclusively disprove either of these scenarios using observations, however unlikely we take them to be. Any form of evidence against either hypothesis could be understood as part of a well-designed simulation or a vivid dream. So, if we’re going to discount the possibility of knowing about other nonhuman minds, on the grounds that it’s possible Descartes is right, we must also say the same about the minds of our family and friends. I don’t think we need to conclusively rule out these radical skeptical scenarios to justifiably believe there are other minds. But what then justifies our beliefs about other minds?

There are many similarities that I can observe between me and other humans. Typically, other humans make eye contact during conversation and can infer the kind of mood I’m in. They can answer questions about what’s on their mind, they scream when they stub their toes and sometimes will laugh at my jokes. They also have similar brains and perceptual organs to my own, not created by a mad scientist, but are products of evolution by natural selection. If other humans behave in consistently similar ways to me across a wide range of contexts, are neurobiologically very similar, and have an evolutionary history, then they (probably) have a mind like I do. The inference from my own mind to other humans is not airtight, but it’s the nearly as strong as can be. The only stronger inference to other minds would involve my perfect clone.  

Applying this inference to creatures outside our species gets trickier. Nonhumans often exhibit different behaviors, vary in their neuroanatomy, and have different evolutionary histories. But still, the inference remains very strong for at least some groupings of creatures. Nonhuman apes like chimpanzees exhibit many of the same behaviors as us, have a complex brain with a neocortex, and they are evolutionarily closely related to us. The common ancestor between chimpanzees and humans can be traced back to around six million years ago, which in evolutionary time is not very long ago. Chimpanzees exhibit complex and flexible behaviors that are best explained by the presence of psychological capacities such as self-awareness, episodic memory and foresight, as well as logical and mathematical reasoning. If we can be at least 99% sure other humans have minds, we can be at least 98% sure chimpanzees do too.

The common ancestor of all mammals lived around 180 million years ago. The timescale is grand enough for some mammals to have evolved significantly different behavioral and neuroanatomical traits, but no such examples have (yet) been discovered. All mammals have the same basic structure including the possession of a neocortex found in us and chimpanzees. So, generalizing this analogical inference to all mammals is also well justified.

When around other mammals, many just find it obvious that they have minds like we do. It’s especially true when considering cats and dogs. We often attribute a wide range of mental states to them without much deliberation. Most people who attribute mental states to their pets don’t know much about the brain or evolutionary theory but clearly recognize the many behavioral similarities between us and them. Certain observed behaviors cry out for an explanation and the possession of a mind seems like the best one. When a cat screams after its owner steps on its tail, we infer that the cat is in pain. When a cat meows after long periods without food, we infer that they are hungry. And when a cat runs away from helium balloons or cucumbers, we infer that they saw the object and are afraid of it. As a cat owner, I could spend all day listing examples.

We, in principle, could learn something about cats, chimpanzees, or other humans that casts serious doubt upon the existence of their minds. We could in the process of doing brain surgery, we discover that other humans have hard drives in their skulls. Or maybe we are approached by men in black suits who provide ample evidence that this world is a computer simulation. Perhaps Descartes is right about animals and God informs us through an act of revelation. But merely imagining ways that others may not have minds, given all the evidence to the contrary, does not create a reasonable doubt.

In surveying other groupings of animals, we’ll encounter some potentially relevant differences. As we will see, it is more difficult to justifiably infer the existence of animal consciousness outside of our mammalian class, and in some cases, it will make sense to deny mentality to some of these other groupings. In the next post of this series, I will evaluate the prospects for four non-mammalian animal groupings: annelids, bivalves, cnidarians, and gastropods. Do earthworms feel pain when hooked? Can clams feel the steam rising from a cooking pan? Is there something it’s like for jellyfish see or smell bioluminescence? Do sea slugs fear their predators?

  

The Chicken and the Egg: The Final Chapter*

 

Contrary to Aristotle, chickens haven’t always existed. And contrary to Genesis, chickens were not created instantaneously in either adult or egg form. Modern evolutionary biology tells us that modern chickens evolved from red jungle fowls in southeast Asia around 8000 years ago. But which came first? The chicken or the chicken egg?

Chic is the name I’ll assign to the first chicken. Around 8000 years ago, Chic hatched from an egg laid by her (non-chicken) red jungle fowl mother. Since the egg that Chic hatched from existed before Chic did, it seems like we can quickly settle the age-old question. The chicken egg came first! Many philosophers and scientists have concluded that the egg-first view is correct for empirical and conceptual reasons (Sorensen, 1992; Papineau, 2006). However, to arrive at the egg-first view, one must establish that the egg that Chic hatched from was a chicken egg and not a red jungle fowl egg. For if Chic hatched from a red jungle fowl egg, the chicken-first view would prevail.

After being contacted by a Disney representative working on the film Chicken Little, the philosopher of science David Papineau offered the following as support for the egg-first view:

"I would argue it's a chicken egg if it has a chicken in it. If a kangaroo laid an egg from which an ostrich hatched, that would surely be an ostrich egg, not a kangaroo egg. By this reasoning, the first chicken did indeed come from a chicken egg, even though that egg didn't come from chickens."

Many might share Papineau’s intuition. But his argument relies upon a principle that can be called into question. In its general form, the principle could be formulated as follows: if an embryo of species X hatches from an egg, then it’s an X egg. I’ll call this the carrier principle.

Upon first glance, one might find Papineau’s example to be intuitive and strong support for the carrier principle. But our intuitions about what type of egg something is seems to shift depending on the details. If I imagine a scenario where a kangaroo lays an egg that looks like just an ostrich egg and an ostrich hatches from it, I suspect most would quickly declare it to be an ostrich egg. But this intuition could be generated merely by the association of ostriches with ostrich-like eggs. Our familiarity with what ostrich eggs look like might make it hard for us to view it as something else. Here are three unfamiliar scenarios that both test and raise doubts about Papineau’s carrier principle.

Genetic Engineering: Suppose in the future, a kangaroo is genetically modified so that it lays hard shelled eggs like birds do, but with a highly unique shape and color. Its eggs are lime green with hexagonal plates. Suppose that at an early stage of development, scientists were to create a small hole in one of the kangaroo’s eggs and exchange the kangaroo embryo with an ostrich embryo. Eventually a healthy ostrich hatches from the egg. According to the carrier principle, the egg was an ostrich egg since an ostrich hatched from it. Additionally, the carrier principle implies that the egg changed its type (from kangaroo egg to ostrich egg) once the embryo exchange took place.

Divine Intervention: Suppose that God decided to use his supernatural powers to spontaneously generate a human embryo inside of a large egg laid by an ostrich. Months go by and a human baby hatches from the egg. The carrier principle implies that this baby did not hatch from an ostrich egg. It hatched from a human egg.

Saltation: Suppose that a red jungle fowl were to lay two eggs identical in size, shape, genetic profile, and except for the embryo, the interior contents are also the same. The first egg contains a normal ostrich embryo, but the second egg contained an embryo with several rare mutations. The mutations significantly change the genome of the embryo to the point that it constitutes a speciation event. So, the second egg contains the embryo of a new species, the chicken. According the carrier principle, the eggs are of different types even though the eggs themselves are identical.

There is an alternative principle informed by embryology and the scientific study of eggs (i.e. oogenesis) that supports the chicken-first view. Following Waller (1998), I’d like to first distinguish between (chicken) eggs and (chicken) embryos. By egg, I mean the white oval-shaped object produced by chickens that found in many American refrigerators and by embryo, I mean the organism that typically develops within the egg. This distinction is important because although chicken embryos are typically carried within chicken eggs, they need not be. When it comes to the first member of a new species, the egg is always a different species than the embryo.  

In this case, the egg that Chic hatched from would have had the genetics of her mother, a red jungle fowl. This is because, as Waller (1998) helpfully points out, the eggs are created prior to the embryo and always have the same genetics as the mother. So, there is a scientific reason for thinking that Chic hatched from a red jungle fowl egg. The alternative to carrier principle, which I’ll dub the oogenetic principle states that if egg x has the DNA of species y, then x is a y egg.

Why should we prefer the oogenetic principle over the carrier principle? One reason is that the oogenetic principle is informed by the of science of genetics and egg development. A second reason is that it fares much better against hypothetical counterexamples. The oogenetic principle tells us that most animals in the real world hatched from eggs of the same species but it also has the virtue of being consistent with the view that animals can hatch from eggs of different species in cases of natural speciation, as well as divine intervention, and artificial genetic engineering scenarios. The carrier principle should be resisted for it entails that it’s (logically) impossible for a creature to hatch out of the egg of another species.

In closing, I’ve argued that the despite the initial intuitiveness and popularity of the egg-first view, the chicken-first view has several advantages. For those who view this as a purely semantic debate, you could eliminate the verbal dispute by following Aristotle and making a distinction between two different kinds of eggs: chicken-produced eggs and chicken-producing eggs (Jansen, 2006). If one specifies the former, then the chicken came first. If one specifies the latter, then the egg came first. The End.

 

Works cited

What came first, the chicken or the egg? the definitive answer. (2006). Retrieved from https://www.theguardian.com/science/2006/may/26/uknews

Jansen, Ludger (2006). It’s Chicken and Eggs again: Vagueness, Quasi-Species, and Evolution. Conceptus: Zeitschrift Fur Philosophie 36 (89):71-77.

Sorensen, R. (2003). A Brief History of the Paradox: Philosophy and the Labyrinths of the Mind. Oxford University Press.

Sorensen, R. A. (1992). The egg came before the chicken. Mind, 101(403).

Waller, D. (1998). The chicken and her egg. Mind, 107(428), 851-853.

 *"The Final Chapter" is an allusion to the subtitle of Friday the 13th Part 4. The series continued well after the "final chapter" (seven additional sequels and a remake), and I expect debates on this issue will not end any time soon.