In What Ways Might Human and Animal Consciousness Differ?

One area of potential confusion when discussing consciousness is what we mean by this term. As I have written previously, Aristotle believed that there were three types of consciousness, with only human beings possessing the rational, "higher" form.

The idea that human beings and their intellectual powers were unique compared to other species continued with the Judeo-Christian philosophical tradition. Yet the last half millennium has seen an erosion of the idea that there is something unique about humans and our place in the universe. This trend began with Nicolaus Copernicus’s demonstration in 1543 that instead of being at the centre of the universe, the Earth is merely a satellite of the Sun, which we now know as just one star amongst trillions of others.

A further blow to our egos came with Charles Darwin and Alfred Russel Wallace’s theory of natural selection, most famously expounded in Darwin’s The Origin of Species, published in 1859, which showed that humans are only one of many branches on the tree of evolutionary change.

We now appreciate that while life itself has existed on Earth for 4 billion years, humans only diverged from our closest relatives, the chimpanzee, much more recently, between 6 to 10 million years ago. And comparisons of human and chimp genes have shown that these are 99 percent similar in DNA sequence. Because of this biological continuity between humans and other species, it is perhaps not surprising that some philosophers and neuroscientists have looked for such continuity in consciousness.

At one level, there is no doubt that at the most basic molecular and cellular levels, but also potentially at higher levels of structure and function, there are many similarities between the brains of humans and other species, and particularly with those of other primates. And in contrast to the distinction made by Aristotle and later philosophers of the Judeo-Christian tradition between the consciousness of humans compared to that of other species, some philosophers of mind and neuroscientists believe there is a continuum of consciousness that extends from bacteria to human beings. For instance, the neuroscientist Christof Koch believes that "consciousness is … probably present in most of metazoa, most animals, [and] may even be present in very simple systems like a bacterium."

The idea that consciousness is something shared by a great number of species underlies a famous essay by the philosopher Thomas Nagel in which he asked "What is it like to be a bat?" In this essay, Nagel makes a number of assumptions. One is that "conscious experience is a widespread phenomenon" present in many animals, particularly mammals. Another is that such experience has a "subjective" character. Turing to the specific question of what it would feel like to be a bat, Nagel argues that because bats have such different sensory apparatus compared to humans, relying much more on sonar to navigate the world rather than a visual system, it would be very difficult to imagine what it would be like to be a bat.

Nagel uses this fact to question whether scientific methods can ever reveal the true nature of consciousness in a materialist, objective, and scientific fashion, or whether this will always be outside the reach of science. In a sense then Nagel’s argument is a variant of David Chalmers’ notion of a "hard problem" in consciousness, but with added emphasis since imagining what it feels like to be a bat is surely is even more difficult than imagining what it feels like to be another human.

But what if Nagel’s assumptions are incorrect? What if the self-conscious awareness that we humans mean when we talk about having a consciousness is not shared with other species? And what if as a consequence, there is no sense that other species can have a subjective sense of themselves as an individual, but rather their "consciousness" will never be more than a mass of feelings and sensations, and as a consequence will be nothing like the individual identity that we take for granted as individual humans?

This may seem like a bold claim, but I think it is consistent with the facts. In particular, I believe it underlies one indisputable difference between human beings and other species, which is the human capacity for transforming the world around us with each new generation. It is this that explains how in the last 40,000 years, human beings have gone from scratching a living from the earth to sending rocket probes to Mars and beyond.

In contrast, no other species on the planet, and that includes our closest biological cousins the apes, has shown the capacity to transform the world in the way that human beings do. Not that this capacity is always a good thing, as witnessed by the fact that human civilisation appears to be heading for catastrophe in the form of global warming, but it is a unique capacity nevertheless. I would argue that it is a direct manifestation of something else unique about human beings, namely our powers of conceptual thought and language, coupled with our ability to design, and redesign, new types of tools and technologies.

Later in this blog, I will look at how these capacities arose as part of our evolution from apes, and what this means in terms of making human self-conscious awareness unique on Earth.