The Chimeric BrainThe Chimeric Brain
All In The Mind
The Chimera - a creature of Ancient Greek mythology - was part lion-goat-snake. Crossing the boundaries between species is everyday in science. To test the therapeutic potential and behaviour of human stem cells, scientists implant them into animals first. But transplanting our brain cells into our closest primate relatives has raised eyebrows, and the prospect of the 'humanzee'. Could this make their brain more human-like? Might this change their moral status in the lab? Top stem cell scientist, John Gearhart, bioethicist Jason Scott Robert, and neuroscientist Peter Schofield join Natasha Mitchell to discuss the scientific and moral questions at the core of creating chimeric brains.
29:50•9 Dec 2006
The Chimeric Brain: Human Cells, Monkey Minds and Moral Lines
Episode Overview
- Chimeras are defined as organisms containing a mixture of cells from two or more genetically distinct individuals, sometimes across species.
- Scientists use human–animal chimeras as “living test tubes” to assess how human stem cells behave, function and remain safe in complex bodies.
- Significant ethical concern centres on inserting human neural stem cells into primate brains and whether this could subtly alter cognition or moral status.
- Expert groups recommend strong caution around early developmental experiments in primates, where human cells could integrate widely throughout the brain and body.
- Guests argue that public trust and honest justification of controversial research are essential, and that vague appeals to future cures are not enough.
“Obviously there's a crossover point where you go from being animal to being human. And I don't know where that is.”
Curious about how science tests the limits of what counts as human? This episode of All In The Mind heads straight into the uneasy territory of human–animal chimeras – brains that are part human, part animal – and asks what that might mean for science, ethics and society.
Host Natasha Mitchell brings together stem cell pioneer Professor John Gearhart, bioethicist Jason Scott-Robert and neuroscientist Professor Peter Schofield to talk through experiments where human stem cells are transplanted into animals, including the brains of monkeys.
The scientific goal is clear enough: as Gearhart puts it, “we need good animal models that we can be assured that the cells we have are going to work and that they're going to be safe.” But once those cells end up in a primate brain, things get morally messy very quickly. You’ll hear the guests wrestle with big questions: Could a monkey’s brain become more human-like?
Is there a point at which an animal with “a bit of human in it” deserves different treatment in the lab? And how many human cells are too many? Schofield notes that “obviously there's a crossover point where you go from being animal to being human.
And I don't know where that is.” Jason Scott-Robert brings a historical and ethical lens, tracing how chimera research moved from quail–chicken experiments to fears about a “humanzee”, and why the public’s gut reactions matter. He also challenges the easy claim that such work is automatically justified by promises of future cures, warning that “that's not going to cut it” for controversial science.
This one’s ideal if you’re interested in how far medical research can and should go, and how our ideas of human dignity, animal welfare and medical hope collide. Where would you draw the line on mixing human and animal brains?
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