Experts say it's probably only a matter of time before technology lets monkeys qualify as legal humans.
In a new article for journal Science, a pair of biomedical law experts say recent advances are beginning to "blur legal distinctions between human beings and other living organisms, between living human beings and dead ones, and between human tissues and cells and nonhuman ones".
Bartha Knoppers of the University of Montreal and Henry Greely of Stanford University say new practises like mixing human and non-human cells and grafting animal organs and tissue into humans, as well as new gene-editing technologies like CRISPR, mean it's time to redefine what a 'human' actually is.
"Against this movable feast of 'human' rights and biological developments, do the classical legal boundaries still matter, and if so, why? Altering the legal meaning of 'human' ultimately affects the foundation for all human rights."
Writing for site phys.org, science journalist Bob Yirka gave the example of a monkey implanted with human organs.
"Can it be argued that a monkey has the same legal rights as human beings if all of its organs (except, perhaps, its brain) have come from a human being?"
Or if a human's genome was edited "into something that may not exist in nature" - would they still be a human, according to the law?
Two years ago scientists in the US created the world's first human-animal hybrids using a gene-editing technology called CRISPR. They added human genetic material to the pig embryos' muscles - but not the brain.
They were destroyed after four weeks of gestation.
"The creation of chimeric embryos by introducing human stem cells to animal embryos often falls between the gaps of the relevant human and animal legislation," said Knoppers and Greely, suggesting adding the word 'substantially' to legal definitions of what constitutes a human.
"Rules that include the word 'substantially' are never fully satisfying," they write. "Nevertheless, in a universe where things blend into each other and living organisms are not cleanly divided into Platonic natural kinds, they may be the best filter we can apply."
The pigs in the 2017 research were only 0.01 percent human, so probably wouldn't qualify. But the pair say it's only a matter of time before a chimera's status is challenged in court.
The full article can be read on the Science website.