What happens when scientists start changing the brain – the very system through which an animal’s mental states are expressed in behaviour?
In a recent study published in Nature, researchers implanted human brain organoids – small, simplified structures grown from human stem cells – into the brains of living mice. Over time, these organoids developed and integrated with the mouse nervous system.
Transplanting organoids composed of human cells into animals, including their brains, is not new. However, previous experiments faced an obstacle: human brain cells grow much more slowly than mouse brain cells, and so organoids are quickly “out-competed” before they can fully integrate with the mouse brain. In the new study, scientists genetically altered mice so that parts of their brain did not develop, then transplanted the human organoids into the vacant space.
The idea of creating human-animal chimeras – animals containing human cells – raises ethical questions, particularly when involving the brain. Various philosophers have argued that as the proportion of human brain tissue increases, we should consider whether the animal could acquire human-like mental capacities – and whether this should change how we treat it. But I argue that serious questions about our ability to recognise animal suffering will arise long before mice gain increased intelligence.
‘Super-intelligent’ mice?
What is it like to be a mouse?
The philosopher Thomas Nagel asked a version of this question about bats. He argued that conscious beings have a specific experience of the world, but that others cannot access that experience from the outside. Instead, we must infer what others experience. With animals, we do this through their behaviour and physiology. But this approach assumes that we understand how what we observe relates to what the animal experiences.
There is nothing morally important about a cell simply because it came from a human. Imagine two mice with identical mental lives and cognitive abilities, one produced using transplanted human cells and the other through a modification involving only mouse cells. It is difficult to see why the first should matter more simply because some of its cells are human.
There are good reasons to doubt that a mouse containing human brain cells could develop anything resembling human intelligence. This is because human-like cognition does not emerge simply from having enough human neural cells. A mouse containing human cortical neurons still has mouse sensory systems, a mouse body and develops according to species specific processes. All of these factors impose constraints on the kinds of cognitive capacities it might acquire.
A mouse might still seem to behave “like a mouse” even as we become less certain that its behaviour accurately tells us how it feels.
In the recent Nature study, researchers reported that mice which received the organoid implant performed on a par with healthy control mice on short-term memory tasks (such as navigating a maze). The researchers did not observe any evidence of altered behaviour or increased intelligence.
This is reassuring. But suppose a chimera grooms less than an ordinary mouse. Researchers can still measure that difference accurately, but interpreting it as evidence of distress means we’re assuming that grooming retains roughly the same relationship to the animal’s experiences as it does in an ordinary mouse.
The same applies to the observation of “normal” mouse behaviour. Since we don’t know exactly how changing the brain will change behaviour, this could make it harder to recognise if the indicators of poor welfare we rely upon are no longer accurate.
What follows for research?
Organoids grown in a dish have been important tools for studying human brain development and disease. But a dish cannot reproduce the environment of a living brain. Transplantation allows researchers to study human brain cells as they develop within a functioning nervous system, potentially providing better models of brain disorders and new ways to test treatments.
This does not, by itself, settle the debate over whether research using chimeras should stop. Uncertainty about an animal’s welfare does not automatically mean that its welfare is worse. It could, in principle, be better. Abandoning potentially valuable research also carries a cost.
Proposals researchers have made for overseeing studies involving chimeras already emphasise careful behavioural monitoring. But this may not be enough. Researchers may also need to establish that the indicators they measure continue to tell us what we think they do. As neural interventions become more extensive, researchers may therefore need to re-validate their methods of welfare assessment.
What happens if we eventually create an animal with human-like intelligence or consciousness? We may never reach that point. But we do not need to reach it before chimeras present a difficult ethical problem. Long before we create an animal that thinks like us, we may create one whose behaviour we no longer understand.
Mackenzie Graham receives funding from The Kavli Foundation, and the National Institute for Health Research.
Awkwardly smiling, a chemist at a waste site is telling me about industrially incinerating corpses. We are crammed into a claustrophobic funnel at the entry point to a rattling shed with high-vis-jacketed workers scurrying to and fro.
The air smells oily and mechanical. With our voices lowered, the conversation is not flowing smoothly. There is a slightly uncomfortable atmosphere, perhaps indicating certain things on our minds that aren’t being said. Passing the waste storage area on my way out, I nervously scan the stacked container rows for the yellow drums which sometimes contain human remains.
You can’t escape the thought of death at these waste incinerators. Potential danger dwells in these spaces through the scorching incineration chambers, uneven steps, machinery flying overhead, and toxic chemicals. Furnace loading points unexpectedly erupt with explosive liquids or a confetti of used bandages and syringes.
Death is also present in the all too real form of anatomical waste. As well as the amputated body parts from living patients, the waste stream includes sealed drums containing heads, torsos and limbs belonging to American body donors.
Parts of corpses travel through industrial incinerators not by accident but by design: they are legal byproducts from biomedical research and development industries and institutions.
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Death seeps into the infrastructural process through abrupt comments, cautious smiles, Excel rows and anonymous yellow drums. It is not known how many anatomical specimens are imported or incinerated in the UK. Britain’s Human Tissue Authority licences over 800 UK-based establishments, who could legally be involved in this process.
But why are they in the UK in the first place?
Many biomedical organisations do not need entire cadavers to conduct their training or experiments. Because British donation programmes tend to accept and retain full bodies, companies and institutions turn to American human tissue banks, which can provide specific parts, such as torsos or feet.
Once an organisation has used a specimen for training, experimentation or tissue extraction, it needs to dispose of it. Sending the imported specimens back to the United States is expensive, but cremating them in regular crematoria in the UK is illegal. In accordance with their consent forms, American human tissue banks do not disclose the identities of the shipped donors to the British organisations ordering them.
Instead of crematoria, designed for funerals and staffed by technicians trained to facilitate disposal of the dead, the specimens come to industrial waste sites, equipped to efficiently obliterate any thing or substance. What interests me in particular is the special “respectful disposal” procedure these waste contractors are sometimes asked to perform.
For my field research I visited three high temperature waste incinerators across England and spoke to 18 staff. I studied who performs the procedures, what spaces and containers are used, and how they look and feel. My architectural drawings and sketches offer a close-up look into these details.
Handling drums of body parts.Mark Shtanov
At the same time, I asked how do the specimens end up at these sites? Based on interviewing anatomists and regulators, I pieced together the wider narrative of how bodies become disposable.
The body parts, arriving at the waste incinerators in yellow drums, come from the world of human body donation. Given the high funeral costs in the United States, donation offers a free alternative for those who cannot afford a funeral, whether for themselves, a loved one, or someone dying in custody. American human tissue banks take care of the bodies’ disposal, often making a provision for part of the remains to be cremated or incinerated as clinical waste.
Prior to exporting the frozen donated bodies domestically or internationally, the human tissue banks prosect the bodies (divide them into parts); as journalist Jenny Kleeman noted in her recent book, “It’s always more lucrative to sell a dismembered body than a whole cadaver.”
The body parts cross the Atlantic into the UK in coolers or cardboard boxes, arranged by type. For example, an order of ten heads would arrive in a “giant cardboard box”, padded with polystyrene, containing ice packs intermeshed with heads, each one wrapped in absorbing sheet, “with a lemon or cherry smell” – as noted by a donor repository technician.
Illustrations from the author’s comic book.Mark Shtanov
The body parts come from donors of different racial backgrounds, which surprised another interviewee, who told me: “To unpack a collection of hands from America that were all different skin tones was my first experience of a black body.”
Once in the UK, the body parts are used for a variety of functions. As well as being used to train doctors and medical robots, the human tissues are sometimes used to make new products, such as leg ulcer dressings or pharmaceuticals, as researchers in this field have documented.
A human body is an invaluable source of knowledge and material which can improve the health and opportunities of the living, lending weight to the Victorian saying: “A body buried is a body wasted”.
However useful, certain specimens and their parts become redundant. In the case of surgical training, a head or a torso normally become unusable after two or three times of defrosting and being practised on.
At this point, institutions face a choice. Some (particularly university anatomy departments) opt to repatriate the specimens to the US or the Netherlands through the same tissue banks that delivered them, treating this as a more dignified conclusion to the donation.
Others, for whom repatriation costs are prohibitive, opt for local incineration, which is permitted by the regulator, the Human Tissue Authority (HTA) – provided the disposal is done with respect and “separately from other clinical waste”.
This may seem clear on paper, but how are these stipulations ensured in an industrial facility designed to destroy things as efficiently as possible?
What respect looks like at 1,100°C
When a biomedical school or business decides to dispose of a specimen through incineration, they need to package it as anatomical waste. The appropriate packaging, prescribed by the National Health Service, is typically a rigid plastic container. These are normally yellow cylindrical drums with red lids. A drum may contain several body parts from different people.
A diagram of the inside of one waste disposal factory.Mark Shtanov
Weight, number of containers and waste description, for example “five torsos”, are included in a form to request a special collection (which is different from collecting other “standard” clinical waste). The lab’s staff seal the body parts in the yellow plastic drums that are “one way” in that they are unopenable after sealing.
Once packaged, the waste contractor’s delivery vehicle collects the drums from the researchers and delivers them to the incinerator site. These facilities overwhelm a first-time visitor. The space is cramped, noisy, and smelly. Dozens of tagged containers jostle with workers in coloured hard hats. “Space is a virtue,” one waste manager told me on a walk-along tour, describing his facility as “a testament to how not to do things”.
Hazard warnings and skull-and-crossbones signs cover every surface – unremarkable to the day-to-day staff, unnerving to a visitor.
The delivery of ‘waste’
Warned in advance about the anatomical waste’s delivery, the staff at one of the facilities I visited prioritised it in the loading queue. At most incinerators, there is no cold storage to preserve organic tissues. The site-based chemist incorporates the body parts into the “incineration recipe”: the order of loading waste to ensure the burning happens at a consistent temperature and any violent reactions are neutralised.
Using a lift or a conveyor belt, sealed waste is brought into a space called the chargebox. From there it is rammed into the incineration chamber. The fumes are stringently filtered before being released into the atmosphere. The ashes are sent to a specialist landfill.
The anatomical waste goes through this process, with some exceptions that are made to comply with the HTA’s requests for separation and respect. In some cases, drums are carefully placed into the lift while the other waste streams are paused – though some of the people I met still thought this was disrespectful, since the drums still tumble down into the chargebox.
A more “respectful” solution, practised only occasionally, is where workers bring the waste directly into the chargebox by dismantling an access hatch and exposing themselves to the scorching heat.
On very rare occasions, the disposal procedure is witnessed by a representative of the biomedical organisation sending the waste, or by an invited religious minister. Although I never witnessed this in person, I interviewed an anatomist who routinely followed the drums to the disposal site and heard of two instances of a religious ceremony from workers at an incinerator.
Drawing of religious minister giving last rites at a waste site.Mark Shatanov
My architectural drawings show these scenes from above and to the side, with no single viewpoint privileged: every drum, every hatch, every worker’s position is given equal weight.
Reading almost like industrial blueprints, the images foreground a key tension in this research: respect is not born from personal sentiment or cultural tradition. It is a set of services, agreed between biomedical researchers and waste managers: improvised last rites that feel counterintuitive in a busy, industrial space.
‘It leaves a bit of a bad feeling’
After learning about respectful disposal at three incinerators, I invited the workers at these sites to group workshops. The aim of the workshops was to get the workers’ opinion on the existing practices and to generate some alternatives. The responses were both pragmatic and effective.
The workshops primarily revealed the workers’ unwillingness to be dealing with anatomical waste.
For example, one male worker in his 40s, said: “Mortuary work is not what we signed up for.”
Anatomical waste makes up less than 1% of what these facilities process. They are normally used to obliterate toxic chemicals and healthcare byproducts. But when it does, the impact lingers. Recounting the incineration of a batch of heads, one worker from Eastern Europe remembered a “bad feeling” when they went home after work.
More senior colleagues managing the process remarked that the rare encounters with the anatomical waste were impacting their colleagues’ mental health. A shift supervisor at one site said: “That just leaves you with everybody going, ‘I don’t feel well now … I need to take a two-hour break at Wetherspoons’.”
A cross section of incinerator lift, showing the drums toppling into the chargebox.Mark Shtanov
But there were some more surprising accounts.
Some younger workers were curious, trying to open and look inside the sealed drums. In response, two experienced colleagues proposed more generic, homogenised forms of packaging, “so that you don’t know what you’re burning”.
That method, they said, would keep “everything enclosed, encased, double bagged … even if lads open it, they can see fuck all.”
Opting to remove acknowledgements of the human remains, the workers came up with intelligent solutions to prevent drums “disrespectfully” toppling over or mixing with other waste. The proposals featured separate doors, cranes to lower the drums gently, and stand-alone mini incinerators operated by a dedicated team.
One incinerator on-duty chemist, in his 40s, remarked that if this was going to be done, then the people carrying it out “are going to bear in mind they are just handling bits of people – it’s not for everyone”.
I also asked workers to draw about their thoughts and what they produced was improvised and to the point. Instead of striving for the right proportions or embellishing the image (as I did), the sketches succinctly focus on what matters: the size of the container, the importance of clear passages, the warning signage to be displayed.
The overarching message from the workshops was clear: the incinerator staff prefer to take a desensitised stance in relation to the anatomical specimens. They want to remain ignorant of the waste, so that they don’t have to worry about it. “What you don’t know won’t hurt you”, remarked a worker in his 50s.
“I don’t think of it as someone’s head or torso … it’s a keg” – said the chemist as we walked away from the rattling shed.
‘Rehumanising the dehumanised’
After the workshops with the waste professionals, I ran interviews and workshops with biomedical and death specialists (which included lawyers, designers, artists and academics). I asked about their role in the industrial disposal of human remains, as well as their suggestions for alternatives.
While broadly aware of the disposal practices, the biomedical respondents were surprised at the ease of human disposal, as well as the injustice towards the imported foreign donors. “This is treating foreign nationals like second class human beings”, said a senior anatomist at a medical school.
A technician from a large donor repository was startled by how easy it seemed to dispose of a dead body if you had access to the right drums. “If you’ve got incineration bins you could quite easily get rid of someone,” he added.
The death specialist group underlined the need for respect. One grief expert responded about dignifying what has already been packaged and classified as waste by saying: “This is re-humanising the de-humanised.”
Some of the death specialists also suggested there needed to be a change in practice and policy.
These specialists wanted the dead to be recognised at the incinerators. But they also felt the real problem started much earlier. Rather than trying to impose respect at an industrial site, they argued, donation consent forms and human tissue policy should be changed so that bodies never end up there in the first place.
The biomedical and death specialists’ views differed from the waste managers’ in the need to acknowledge the presence of human remains. The workers’ sobering proposals for generic, double-bagged containers were met with a different vision of buckets with “calm design”, embellished with iconography like “fragile” and with soft padding.
Whereas the anatomists and death specialists suggested recital of poems, the playing of ceremonial music and creation of soft rooms for mental health support, the waste workers would have none of this. One told me: “I prefer not to think whose leg or torso that is.”
These contrasting positions reveal professional divides along the trajectory of a donated body. What is perceived as a person in a laboratory or a standardised scientific product at a tissue bank, is seen as unpleasant waste in a disposal context.
I drew this full trajectory as a comic, stitching together the divergent viewpoints. What individually appears ad-hoc turns out to be a convenient business plan. The overall picture reveals a system designed so that no one person holds the whole story.
A mocked up yellow drum created by the author for an exhibition of his work.Mark Shtanov
I came away from my experience thinking that the waste personnel’s concealed labour deserves acknowledgement. Similarly to the noble act of donation: their work reshapes our living bodies through the emergence of new doctors, medical techniques and pharmaceuticals. Anatomical waste is part of a complicated process that can help improve society in different ways.
Parts of donated bodies are increasingly unlikely to go through a traditional funeral or cremation. But as biotechnologies advance, more human tissues will end up at industrial incinerators like the ones I visited – their last stop. The yellow drums will keep coming.
As one worker put it: “What you don’t know won’t hurt you.”
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Mark Shtanov received funding from the University of Manchester as part of SEED Scholarship.
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