When science writer Carl Zimmer had his genome sequenced – every molecular “letter” of his DNA read and recorded – one of the scientists who helped him to understand what it meant indulged in the rhetorical flourish beloved of genomics researchers. Pointing at him, the scientist declared, “That is not Carl Zimmer.” Then he pointed to the hard drive containing his genome data. “This,” he announced, “is Carl Zimmer.”
It wasn’t (I hope) a comment designed for deep philosophical reflection, but its unguarded nature makes deconstruction all the more rewarding. We have been prepared for sentiments like this ever since the Human Genome Project – the international initiative that ran from 1990 to the early 2000s to read an entire human genome – was advertised as an effort to understand “what makes us human”. The project, we were informed, was reading the book of life. It would reveal the blueprint of humankind. And so on.
What Zimmer was told puts that notion into its starkest expression: the body, the brain, the whole physical being of a person may be divested of personal identity and be reduced to a mere housing for, a husk of, the true individual. Our personhood itself, in this narrative, resides in abstract information that can be stored on the bytes of a computer disk. It is rather as if René Magritte were to reverse the message of his famous painting, insisting that this physical object in his hand were not a pipe at all because its essence of pipeness had been captured in the picture.
It is of course the genetic analogue of “downloading our brains”: another strange and frantic flight from our fleshy nature. In this narrative, the body is de-authenticated and personhood becomes a computer code. You can put it in a book.
It’s worth understanding how we got to this point. One reason, I believe, is the allure of the comprehensible. Human beings are frightfully complicated. To understand how the fertilized cell becomes an embryo, a fetus, a person, is a quest on which we have only just begun. Merely understanding how the body (usually) gets the right shape, let alone why some deviations from that shape are fatal while others remain viable, is a tremendous challenge. When we come to consider how the brain, the most complex object we know, becomes wired and orchestrates our behaviour from a mixture of contingent growth, sensory and environmental inputs, and genetic predisposition … well, then we struggle even to erect a multi-dimensional frame of reference for articulating the problem. The idea that all of this information can be reduced to an “instruction manual” encoded in four symbols that fits onto a hard drive promised to make the problem manageable. But it is an illusion.
There are other forces at play. If we believe that the real self can be put into a computer memory, we need no longer be troubled by corruption of the body. And of course mortification of and disgust for the flesh has a long and deep history in Western culture, where “carnal” carries a whiff of the debauched and morally corrupt. Our meat-self is animal, while the cerebral – I mean metaphorically, not the icky grey matter inside our skull – elevates the human to a higher plane. Bodily disgust is quickly (and enthusiastically) taught and quickly learnt. Sex is a dirty necessity, even with our best efforts to sanctify bodily union via a socialized morality tightly policed by taboos. The same with death: grief is tinged with disgust and anxiety about decay, which our death rituals do their best to allay with embalmings and professionalization of bodily disposal. One of the worst (and best) horrors is the return of the dead, smelling of the charnel house.
Yes, when you think about the history of the body, it is no surprise at all that we have become so determined to find in modern biology permission to dematerialize the self into information. Such a self is timeless and perfectible – for information can be copied, preserved, even updated and edited (not to mention copyrighted and sold). Flesh is a mortal coil, but data is an eternal stream.
I don’t think that anyone, faced with the warm, breathing person and the cold metallic hard drive, would have a moment’s hesitation in deciding which is the real Carl Zimmer. He, like each of us, is not just made of flesh but is written into it. He is the fellow who enjoys a latte in New Haven’s Book Trader café, not the binary code that allegedly encrypts those predilections and memories.
The temptation is to say we “inhabit” our bodies, even that we are “trapped in them”. But that would be to collude with the fiction that the self is a thing that is housed, and perhaps that needs to be set free – that it could enjoy an independent existence, if only we can find the key to the exit. But we are our flesh, in the same sense that England is its hills and dales, its rivers and its cities and people. All of these things change over time; we never step onto the same England twice. The flux is part of the definition.
But even while we should reclaim our identity from the genome-fantasists, we have to recognize that modern science complicates this insistence of returning to the body. For the body is far more plastic than we thought. I know that mine is, because I’ve seen some of it growing in an incubator across town, behaving as though it “wants” to become another superorganism like me, with thoughts of its own, searching with questing stumps of neural tissue for a body that is not there. My piece of flesh didn’t get, could not yet be given, that opportunity. But it’s by no means obvious that this is not, in principle, an option.
This new understanding of the capacities of human flesh disturbs old philosophical questions. Pretty much all of the traditional philosophies of self, from Descartes to Hume to Sydney Shoemaker, are predicated on the uniqueness and integrity of the individual.1 But I seem now forced to accept the possibility (even if the actuality remains distant) that a piece of my arm could become an embryo, even without an act of conception: that pretty much every cell in my, or your, body is a potential person, or at least the progenitor gamete of a person. What does that mean for the religious ethics, not to mention the legalities, of the self? (If you can buy Elvis’s sweat on eBay, does that mean you could “grow your own Elvis”?)
In the light of this protean ability of our flesh to grow, and keep growing, perhaps in any way we choose to guide it, how can we develop a moral framework for adjudicating life, death and identity? Where, in this seething mass of life, are we? Are we perhaps just a particular realization of some more general “essence of us” imbued in our living flesh?
What we seem to be seeking here is the root of our individuality. It may come as something of a shock to discover that biology fails to locate it.
* * *
John Donne’s celebrated claim that “No man is an island” might be read retrospectively as a rearguard action, a spirited defence of the social self against early modernity’s assertion of the independence and isolation of the individual. As Daniel Defoe’s Robinson Crusoe – the first great fable of that modern view – illustrated, to be an island to oneself was to experience the contradictory terrors that you might never again enjoy human intercourse and that your self-sufficient and even comfortable isolation would be violated.
Pace Donne, our existence is totally and unavoidably solipsistic. We are trapped in our minds, ignorant of all that evades our senses and able only to infer, and never to experience, the minds of others. It is this (generally benign but potentially hellish) internal imprisonment that literature, art and some aspects of spirituality seek to alleviate. The mystery, though, is how the biology of mind and body conspire to assemble our illusion of unity. How are all our sensory inputs, each taking finite but differing times to process, integrated into the sensation that we are each a single conscious entity alive to the moment? The answer to that question still lies somewhere within the black box we label consciousness. We can only assume that the mind has evolved this capacity because it is a useful one: that perhaps a feeling of identity and individuality rewards us with a sense of agency, enabling us to make our way in the world.
What’s odd, though, is that this should be necessary. We do not and presumably cannot know what it means to be a bat, as Thomas Nagel famously observed. But it’s far harder to imagine what it is like to be a fungus, and it isn’t clear that there is much meaning in asking what it is like to be a slime mould like Dictyostelium discoideum, which is both single-celled and multi-celled. It’s doubtful there is anything much to be “like” when it comes to single cells. And yet these organisms make their own way in the world too, and with considerable success. There seems no reason to suppose that fungi, plants and bacteria, at least, have any need for “consciousness” in the way we know it: a feeling of individuality that goes beyond the ability to respond to stimuli in a self-preserving fashion.
Regardless of how or even why the human mind conjures the perception of individuality, it evidently does so. And this predisposes us to see it as a fact of nature. It stands to reason that there are also individual dogs and bats, and even individual cells. This singular existence is what the very word “organism” is supposed to invoke.
But even though science has sometimes been called “organized common sense”, it can be frustratingly hard to make common sense scientific. When you really get down to it, the concept of the individual is all but impossible to define in scientific terms.
Our first instinct may be to define it with reference to the boundaries of the body. (Even bacteria have edges, right?) But my mini-brain put paid to that, as far as I’m concerned. If those tissues were not somehow a living piece of me, I do not know what they were. But it is clear in any case that my body is not just an assembly of human cells but a complex ecosystem composed of cells from hundreds of species. And as we’ve seen, the collective action of this community (especially but not exclusively the microbes in my gut) affects not only my metabolism but also my mood and other mental states – qualities that feel very much a part of the subjective “me”. At any rate, “I” would be in a bad way without them.
This is the norm in nature. Symbiotic unions of cells from different species, often sharing metabolic and developmental duties, are everywhere. Plants acquire their nitrogen – a vital element for metabolism and growth – from the bacteria (rhizobia) in their root systems, where there are also fungi (mycorrhizae) to be found that carry out other essential functions. Corals depend on the nutrients provided by their symbiotic algae; some sponges contain 40 per cent by volume of bacteria.
“It seems,” writes microbiologist James Shapiro, “that we need to think of organism as a term that has a much broader community-based or systemic meaning than the significance given by traditional perspectives based on the idea that each organism has its own separate, vertically inherited genome.” It’s no surprise that it would take a microbiologist to see beyond the traditional perspectives – for these folk are fixated precisely on life at the level of the cell and its environment, where the meanings of “life” become complicated. We could of course tell a nice inspirational story about all this “cooperation”, to counteract the ruthless narrative of a “selfish” Darwinian struggle; but that seems neither essential nor particularly useful. Grant that random genetic variation subject to varying degrees of natural selection happens among proliferating cells, and evolution follows. Biology is what it is, and sometimes we should resist making it any more or less than that.
The ubiquity of symbiosis makes it clear that defining an individual organism in genetic terms doesn’t generally make sense either. It will hopefully be clear now that the idea that our genome is the “essence of us” is fallacious from the outset. But it’s not an essence of our organismic individuality either. Symbiosis means that we need things our genomes can’t give us. As more and more species have their genomes sequenced, we are regularly encouraged to equate species with sequence, and sequence with organismal identity. But the genome of no complex organism contains all it needs for healthy growth and survival.
Even if our genome is not “complete”, isn’t it at least unique? That is the notion gene-sequencing companies push so hard, aiming to flatter: let us reveal the uniqueness of you. Of course, they know already that this will do nothing to flatter identical twins (quite the reverse, I’d have thought). Neither will it work for the many people who have mosaicism or chimerism in their cellular make-up (see here). And it certainly won’t work for a definition of biological individuality in general, being irrelevant to bacteria that replicate asexually (and thus clonally) by cell division. No, there is no innate connection between the individuality of the organism and its genome – no one is going to propose, I think, that those cloned macaque monkeys are somehow “the same individual”. Indeed, one of the weakest objections to human reproductive cloning (about which there are also some more persuasive concerns) is that it disrespects the “integrity” of a human being to give them the same genome as someone else. This is really just an expression of Scott Gilbert’s myth of “DNA as soul”.
Faced with these facts, some biologists have sought other ways to define biological individuality. How about the immune system, which after all is set up precisely to distinguish “self” (safe) tissues, cells and fragments thereof from “non-self” (potentially dangerous)? But immunity is not just protecting the organism from outside threats; it also looks for those coming from the inside, such as cancer cells, symbionts that get out of hand, even fetuses that the maternal body rejects. As Gilbert and his co-authors have written, the immune system is not merely the body’s “armed forces” but also its “passport control”: do you have the correct documentation to be here? “Immunity,” they write, “does not merely guard the body against other hostile organisms in the environment; it also mediates the body’s participation in a community of ‘others’ that contribute to its welfare.”
In some desperation, a few researchers have tried to find a behavioural definition of the individual: it is that which is “autonomous” and “end-directed”, acting towards some goal. But as usual in biology, introducing teleology causes more problems than it solves. Does the amoeba have a goal?
This might seem like pedantry. After all, we are individuals! But if that’s so, philosopher Ellen Clarke has pointed out, then surely a biology worthy of the name ought to give some account of what it means. Individuals, she says, are “central to the inner logic of evolution by natural selection” – since it is the individual that evolution “sees”, whose life or death determines whether the genes are passed on. But evidently, Clarke concludes, “we lack a theory telling us which lumps to count” in evolution and life.
This is because what “counts” (and what to count) depends on what questions we are asking and what scale we are observing. In short, there is not the slightest reason to suppose that what “counts” for our cells is what “counts” for us, any more than to think that what “matters” for quarks is what “matters” for planets. As a result, it should be no surprise that cell biology messes with our sense of self.
The best illustration I have seen of this fact is supplied by an organism none of us is in any hurry to encounter: the Portuguese man-of-war. This jellyfish has a nasty sting, its dangling tentacles loaded with a venom strong enough to kill a fish. But the Portuguese man-of-war is not actually a jellyfish at all. It looks pretty much indistinguishable from those organisms. Yet each “organism” is not an individual but a colony of small multi-celled animals called polyps. There are several “colonial animals” of this kind, collectively called zooids; corals are another example.
A Portuguese man-of-war: an “organism” that is truly a colony.
We are not like Portuguese men-of-war (if that is the plural); our cells are fully integrated, not apportioned into separate animals within the body. But that doesn’t make us any the less a colony: a collaboration of cells, some of them human and some not, that has evolved this rather wonderful and mysterious tendency to consider itself a unique entity. Does the Portuguese man-of-war harbour, in its collective polyp-mind, any comparable illusion, I wonder?
* * *
Complicating the notion of individuality in biology is more than a nuisance for theories that seem to demand it. It pulls up at the roots the concept of nature that has grounded the discipline.
At one level, retaining the idea of the living world as a collection of individual, self-contained organisms is not only sensible but necessary – in much the same way as it is necessary for us to hold onto the idea of objects in a microscopic physical world imbued with quantum flux and devoid of hard edges. At the microscopic scale, we know that the large objects of classical physics – a book, a pen, an aircraft carrier – are fuzzy, their boundaries being a constant traffic of atoms. But it’s worse than that, for quantum physics tells us that the subatomic particles making up matter can, in theory, pop up anywhere in the universe if we choose to look for them. It’s just that some locations are much more likely than others. Efforts to make sense of quantum mechanics suggest that particles become entangled and interdependent once they interact, or that every particle “feels” all the others, or that particles and objects are constantly splitting into copies, or other things that make a nonsense of the clear-cut identities and edges of everyday perception. Yet if we don’t maintain that fiction, not only does science become all but impossible but it fails in its job of offering a coherent description of our perceived reality.
So too with the biological individual: it would be foolish to abandon the concept. What we have to remember when we invoke it, though, is that we are doing so in order to formulate a picture of one level of the world. We are not voicing some fundamental truth. Indeed, if biology teaches us anything, it is that it is unwise to generalize about pretty much anything that is alive (including what we mean by that word). This is not because biology is lawless, but on the contrary because evolution is so central to it. Any way nature can “find” to impart a selective advantage is likely to be adopted, and it really does not matter what biologists have proclaimed to be allowed or forbidden: biology is no place for sacred cows or dogmas. If we truly believe in evolution, as of course we should, then we won’t try to constrain it with supervening rules proclaiming this or that to be impossible. We will trust that it finds good strategies.
Darwinian evolution by natural selection amid random mutation is one of the main engines of biological evolution, and it makes sense of a great deal that we see in nature. But it doesn’t make sense of everything. Evolution is driven by other things too: for example by random drift in which random mutations occur without selective pressure. Non-Darwinian change happens, as for example when some cells actively modify their genome (for example, its propensity to incur mutation) to improve survival and growth, or when cells that have been modified by some environmental influence pass on the modification to progeny cells. There is no reason to see these things as controversial or challenging, let alone as “disproving Darwin”, for the simple reason that there is absolutely no “biological law” that would forbid them.
This is why narrative is so hazardous in biology. We seek simple stories – that genetic information flow is one-way, that genes are in a selfish struggle for survival, that genes make us who we are – because that is what we humans do. We can make them dogmas or laws if we like, but biology doesn’t give a damn. It will do what suits it, and what it does is too complex, has too many exceptions, too great an inventive impulse, for any metaphor or narrative to fit perfectly.
So it is with biological individuality. If it proves to be a convenient fiction, that doesn’t demolish biological ideas which draw on it (though it may well complicate them). Individuality is often a useful approximation at the level of large organisms like us – and no doubt that is why our brains have evolved to conceptualize the world in these terms. But it isn’t a terribly useful notion for the cell. It is sometimes rightly said that if we were conscious electrons, we would have no concept of objects. Likewise, if we were conscious cells, we would not recognize individual organisms in the way that we humans conceive of them. We are not individuals all the way down.
Our cells are telling us this. It’s worth listening to them. To use one of those hazardous human-shaped metaphors (but I think the cost is worth it): cells have a kind of wisdom, and we should allow ourselves to be humbled by it.
* * *
My little neural organoid was not really a “brain in a dish”. There was never the slightest suggestion that it was conscious, or capable of anything that warranted being called cognition.
My brain organoid, seen through a microscope, with cells stained to show their identity. Neurons appear as red, and can be seen organized into layers like those in the cortex of the brain.
But just suppose we had been able to give it the vasculature and the developmental signals it would need to keep growing and to become even more truly brain-like. Or imagine we could grow neural cultures that resemble different parts of the brain and wire them together into a “brain assembloid”. We still have no theory, or even a clear definition, of consciousness, but there is some reason to believe that it might arise in a specific region of the cortex. What if we could grow a brain organoid closely mimicking this region?
What kind of status should such a structure be afforded? Might it become capable of anything deserving to be called thought, or even reason? What would be the nature of its experience? And “who” would it be?
When I embarked on the Brains in a Dish project for Created Out of Mind, I considered that it would be foolish and presumptuous to ask such questions. As my mini-brain took shape, however, a paper was published in Nature by several leading neuroscientists and bioethicists who took the possibilities seriously. These things may be a long way off, the authors said, but we need to think about them now. They argued that “as brain surrogates become larger and more sophisticated, the possibility of them having capabilities akin to human sentience might become less remote.” Such capacities “could include being able to feel (to some degree) pleasure, pain or distress; being able to store and retrieve memories; or perhaps even having some perception of agency or awareness of self.” We need to think what a regulatory structure for such research should look like, says Hank Greely (one of that paper’s authors) – and we have perhaps just 5 to 10 years before the questions become urgent.
Today’s mini-brains have nothing like the complexity of the human brain. There are typically a mere 1 to 2 million neurons in their pea-sized mass, for example, compared to the 86 billion in the adult brain. What’s more, the neurons in brain organoids are much less active, sending out signals (“firing”) at just 3 to 4 per cent of the rate of those in the real brain and possessing little of their complexity of shape and structure.
But it’s not absurd to entertain the idea of brain organoids with a degree of awareness. The numbers alone can be deceptive. For example, 80 per cent of the neurons in our brains are in the cerebellum, but it is possible for consciousness to develop even for a person lacking a cerebellum entirely – as was the case with at least one unfortunate Chinese woman born with that extreme developmental defect. And while brain neurons need sensory experience not only to build up a mental model of the world but to function properly at all, this could be supplied as an organoid grows. A brain organoid grown by one team of researchers, for example, began to develop a primitive kind of retina, and shining light on this area stimulated activity in the neurons. Madeline Lancaster has coupled the neurons of a brain organoid to muscle tissue and has seen muscle responses to the neural activity, in principle giving the organoid a capacity to affect and respond to its environment.
Christof Koch, another of the authors of the Nature commentary, questions the status of the mini-brain in rather confrontational terms: “We have to start thinking about it: is this thing in pain?” It’s slightly shocking to realize that even experts don’t know the answers to such questions. What can “pain” even mean in the absence of neuroreceptors through which pain is sensed by nerves in the body? (There are none of these receptors in the brain itself.) “Without knowing more about what consciousness is and what building blocks it requires, it might be hard to know what signals to look for in an experimental brain model,” the Nature authors admit.
Who would determine – indeed, what would determine – the life or death of a sentient brain organoid? Will they need to have “guardians” appointed to look after their welfare, in the same way that individuals may be appointed for children involved in custody disputes? Would we owe sentient mini-brains a duty to provide a stimulating environment, meaningful memories and relationships? Do we have any idea what the notion of identity could mean to such a … thing? Entity? Person?
* * *
My own mini-brain has, however, had its day. Once Chris and Selina had grown it, they fixed it in formaldehyde, embedded it in a gel, and sectioned it for staining and imaging. I don’t think I neglected any duty of pastoral care to this living entity, although I can’t entirely shake off some lingering sentiment about the matter.
Is that the end of my adventure in the propagation of my own flesh beyond my all-too-mortal body? I wonder. “We still have your fibroblasts and your induced pluripotent stem cells in the liquid nitrogen,” Chris tells me – “frozen in time, ready to be revived …”