麻豆传媒

LAST year, they had inserted a human brain gene into monkeys. These 11 monkeys outperformed typical monkeys in tests of short-term memory, and their brain development more closely resembled that of humans. Are these animals still fully monkeys? Or are they something else? Something human?

Plenty of other experiments have blurred the line between what is human and what isn鈥檛. Research teams have created pigs with human genes. Clumps of human brain cells have been grown in dishes, and the cells can communicate with each other. Then there are 鈥渟ynthetic human entities with embryo-like features鈥� 鈥� structures made from human stem cells that look like early embryos.

Should all these entities be protected by law in the same ways humans or human tissues are? Some researchers think so, and are proposing a new legal definition for such entities: 鈥溾��. If the entity is more human than not, it should be granted human rights, they say. But this raises questions as to how exactly we define humanness, and what that means for entities that fall outside that definition.

It is only a matter of time before we will be forced to decide, say Bartha Knoppers at McGill University in Montreal and Hank Greely at Stanford University in California. 鈥淎t some point, courts will be faced with the questions: is this tissue human or not? Are these remains human or not? Is this living organism in front of us human or not?鈥� says Greely.

He and Knoppers suggest that the term substantially human could be applied in cases where the line is blurred. 鈥淚t means that just because something is not 100 per cent traditional human, he or she should still be viewed as human for purposes of human protections,鈥� says Greely.

The pair are being intentionally vague. Whether an entity is substantially human or not should be a judgement call to be made by individual countries. The decision could be influenced by a nation鈥檚 culture and values, in the same way that the law uses terms like 鈥渦nreasonable鈥� or 鈥渂est interests鈥� without precisely defining them, they say.

Others think we need firmer guidelines. 鈥淩ules that include the word 鈥榮ubstantially鈥� are never fully satisfying,鈥� says Jeantine Lunshof at Harvard University.

Inevitably, some will want to come up with a test of 鈥� or at least a guide to 鈥� humanness. One starting point might be the genome. Our genes certainly make us human, in terms of coding for human features. But when we take a closer look, there is a lot of similarity between a human genome and that of a chimp, for example 鈥� or other animals, for that matter. We share 97.5 per cent of our genes with mice, according to one estimate.

鈥�97.5%
Estimated percentage of genes humans share with mice鈥�

However, genes alone can鈥檛 determine legal status. Embryos are genetically human, but in most countries an early embryo doesn鈥檛 have the same rights as a baby. The same could be said of human cells cultured in a lab. On the other hand, gene-edited people like the three CRISPR babies born in China are very much human, even if they have newly introduced genetic mutations. 鈥淚f you take a gene-centred view of humanity, arguably they are outside it,鈥� says Greely.

He worries that such criteria could be used to argue that some individuals aren鈥檛 fully human. 鈥淥ur species has an often-expressed willingness to find and magnify minor differences amongst ourselves into sources for hatred and discrimination,鈥� he says.

Instead, we need to think about what makes humans 鈥渕orally significant鈥�, says Julian Savulescu at the University of Oxford. 鈥淭he idea of something being 鈥榮ubstantially human鈥� is a step forward because it shows there isn鈥檛 a bright line between human and non-human,鈥� he says. 鈥淏ut I think we鈥檒l have to go further than that and start to think about the properties that are especially valuable.鈥�

Such traits are thought to include things like self-consciousness and the ability to form complex relationships, says Savulescu. 鈥淗ow do you evaluate that in a life form that doesn鈥檛 speak our language and communicate in the way we do?鈥� he asks.

It is a pressing question. Greely thinks that the first legal cases will surround the treatment of substantially human tissues. If a human organ is grown in a lab from an individual鈥檚 cells, how should it be dealt with and disposed of? 鈥淭here are statutes that require human remains be treated with certain kinds of respect,鈥� he says. For example, in the UK, human tissue must be disposed of in accordance with the donor鈥檚 wishes, as far as possible.

Enter the chimera

Savulescu, however, thinks the first legal cases will involve human-animal chimeras: animals that contain cells from two species.

Human-pig chimeras are already being grown. These contain cells that could allow them to develop human organs, although, so far, the resulting embryos have been destroyed before this happens. The idea is that transplant organs could be made in pigs using a person鈥檚 cells, allowing them to circumvent lengthy waiting lists for human-donated organs. In theory, the organs should be human enough to avoid being rejected by the recipient鈥檚 immune system.

But at what point do the pigs themselves become too human to be used in this way? Mice with human brain cells are smarter than typical mice, and perform four times better on memory tests, for example. There is a concern that should these pigs accidentally develop human brain cells, they might also develop some of the 鈥渕orally significant鈥� characteristics of humans, such as self-consciousness. 鈥淲e have to get off the fence and decide what it is about life that makes killing that being especially wrong,鈥� says Savulescu.

Other potential legal cases will surround the physical and cognitive enhancement of humans, says Jennifer Chandler at the University of Ottawa. Technically, we humans have been cognitively enhancing ourselves for as long as we have been around. Education improves our thinking, for instance.

But newer approaches that involve stimulating the brain using implanted devices start to merge human and machine, she says. Brain implants are already being used to treat conditions like epilepsy and Parkinson鈥檚 disease, and are currently being investigated in a range of other conditions.

Some neuroscientists are attempting to tweak the way those implants work to enhance cognition. One team has already used a device originally implanted to treat epilepsy to improve memory in a group of volunteers. A company called Kernel is working on a brain implant to boost human intelligence, while Neuralink, which Elon Musk co-founded, aims to connect people鈥檚 brains to computer-based artificial intelligence.

鈥淲e have to get off the fence and decide what about life makes killing it wrong?鈥�

Because these devices target our brains, they have a greater potential to affect the characteristics that make us human, says Chandler. Hip replacements and insulin pumps are one thing, but 鈥渋t seems somehow a little different when you鈥檙e talking about an implant that鈥檚 meant to directly modify mental functioning鈥�, she says.

In the future, the law may distinguish between 鈥渆nhanced鈥� and 鈥渦nenhanced鈥� humans, says Chandler. 鈥淧eople fuss about cheating,鈥� she says. 鈥淚f people cognitively enhance in the context of a competition, does that break the rules or not?鈥� Courts may eventually be forced to decide, she says.

Some futurists predict that we will one day be able to upload the contents of our brains onto a computer. Would such an upload be human? 鈥淚 guess that would be a place to apply the substantially human test that we propose,鈥� says Greely.

In the meantime, there are plenty of scientific and technical achievements to keep ethicists and lawyers busy. 鈥淲e should err on the side of generosity: if we鈥檙e uncertain of the status, we should grant the status,鈥� says Savulescu. 鈥淯nless we鈥檙e certain this thing is closer to a pig than it is to a human, we should treat it as a human until we know more.鈥�