What does it mean to be human?

Biomedical law experts say changing technology may require a less stringent definition.

We are all human, but what does that mean in the modern world?

Philippe Beyer / EyeEm, via Getty Images

By Paul Biegler

The pace of biotechnology research is blurring the bounds of humanity so rapidly that two US scholars are calling for a rethink on what it means to be legally human.

Writing in the journal Science biomedical law experts Bartha Knoppers, from McGill University in Canada, and Henry Greely, from Stanford University in the US, say technologies that mix non-human and human cells, such as CRISPR, xenotransplantation and chimeras, mean a less stringent definition of “human” will be needed going forward.

For the purposes of ascribing all-important human rights, set out in the United Nations Universal Declaration of Human Rights, we should only require the organism to be “substantially” human, they argue.

One biotech prompting the taxonomy shift is the human-animal chimera.

Scientists have used DNA editing to make animal embryos that lack an organ, with the aim of inserting human stem cells into the embryo to grow a transplantable human organ in its place.

In July, Japanese scientists were funded, for the first time, to gestate mouse embryos containing human cells to term in a surrogate animal.

Another tech adding to the cellular traffic between species is xenotransplantation. US start-up EGenesis recently secured $100 million funding for its program to genetically modify pig organs to make them suitable for human transplant.

Such developments, write Knoppers and Greely, “challenge the animal-human species divide”, posing a headache for global legal systems whose pedigree traces back to the Roman axiom “Hominum causa omne jus constitutum est” – “All law is created for the sake of men”.

The advances raise the curly question of whether, and why, a person with pig parts can still claim membership of the “human family”. Knoppers and Greely think they can, with some rejigging of our jurisprudence.

We should start, they say, by recognising that the definition of “human” is already permissive. We tend to think of Homo sapiens as having two arms and legs, but we don’t eject them from the species if they lose a limb.

Likewise, missing a kidney, even if it is replaced with a porcine version, shouldn’t disqualify you from humanity – more so given the number of legitimate humans already wandering around with pig heart valves.

That argument leverages our intuition that being “substantially” human is enough. And once you’re OK with the looser term, it gets easier to deal with a range of other taxonomy issues.

The United Nations Educational, Scientific and Cultural Organisation (UNESCO) holds that the human genome “underlies the fundamental unity of all members of the human family”.

But just what makes a human genome is being challenged with technologies such as CRISPR, which artificially tweaks our genes, most notoriously in the creation last year of the world’s first gene-edited humans – twins Lulu and Nana.

If there were any doubt as to the twins’ human status, the fact that CRISPR leaves them “substantially” human might quash it.

Another candidate for entry into the humanity club is possession of a conscious, self-reflecting brain. But scientists are now creating mini-brains from human stem cells in the lab – in one recent case, generating brain waves comparable to those of a late-term foetus.

There is no evidence, however, that these are sentient, let alone conscious, which would seem to earn them a “fail” on the substantially human test, even without mentioning the fact they don’t have a body.

It is all complicated by the dizzying rate of science progress and the worryingly subjective nature of the term “substantial”.

But, the authors rejoin, the law gets by pretty well now with slippery terms like “unreasonable”, so this is nothing new. Indeed, there are already legal precedents for the use of “substantial” in copyright and data protection law.

What we must do, they conclude (albeit with a dash of what philosophers strictly call question begging) is to be OK with a bit of fuzziness creeping into what it means to be human:

“In practice, our human families do not always meet exact definitions with perfect edges, but we can see substantial connections among them.”

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Paul Biegler is a Eureka-Prize winning journalist, bioethicist and former physician writing on all things health and science.
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