Whatever happened to the human clones?

For a few years around the millennium, the news was full of cloning stories – many of them anticipating the application of the technology to human beings. And yet, as of 2018, no human clone has ever been born (not to the best of our knowledge, anyway). In a fascinating, if somewhat horrifying, report for MIT Technology Review, Antonio Regalado explains why.

It’s not that the technology hasn’t made progress. Several other mammalian species have been cloned since 1996, including Barbra Streisand’s pet dog, horses for an entire Argentinian polo team and, just last year, the first primates – a pair of crab-eating macaques at the Chinese Academy of Sciences in Shanghai. (The macaques, named Zhong Zhong and Hua Hua, are pictured above.)

So why no clones of that other primate species, H. sapiens?

“In the basic cloning procedure, like that used to create Dolly the sheep… scientists take an entire adult cell and inject it into an egg that’s been relieved of its own DNA. The resulting embryo is a clone.

“But that process is inefficient. In many animals, only one in 100 cloned embryos ever leads to a live birth. Some embryos expire in the IVF dish. Others wither in the womb. Of those that are born, a few suffer from abnormalities and quickly die.”

To put it very crudely, cloning requires three basic ingredients – a cell with DNA from the individual to be cloned, an egg (without DNA) and a surrogate mother. The first of those is not in short supply – a skin cell might do. Eggs are much harder to come by, they can be readily harvested from animals, but human cloning requires women willing to donate. That raises all sorts of ethical questions – and the further requirement for surrogate mothers all the more so.

Even if a would-be human-cloner didn’t care about the morality (and, indeed, the legality) of making such arrangements, the practical challenge would be magnified to unfeasible levels by the high failure rate of the cloning procedure. But what if the failure rate can be reduced?

Regalado reports on a recent breakthrough, which enhances our ability to unblock the gene functions required for the successful development of a cloned embryo:

“…Yi Zhang, a stem-cell biologist at Boston Children’s Hospital and an investigator at the Howard Hughes Medical Institute… has found chemicals that, if added to an egg, can help release the blocked genes.

“In Zhang’s hands, addition of these ‘modifiers’ has led to dramatic improvements in cloning— wiping out barriers present in the adult cells. Zhang first tried it with mice. Instead of about 1 percent of cloned embryos leading to a mouse pup, he says, now 10 percent of them do.”

It was this technique that enabled Zhong Zhong and Hua Hua to be born. It has also been tried with human cells, though not with the same intention:

“To be very clear, Zhang isn’t planning to make babies. Instead, his objective in cloning speck-size human embryos is to obtain their stem cells. Known as ‘therapeutic cloning,’ it’s a way to create powerful embryonic stem cells genetically identical to those of the donor adult—say, as a source of replacement tissue.”

Therapeutic cloning isn’t very therapeutic for the cloned embryos – but, in theory, they could, like the macaque embryos, be implanted in a womb and taken to term:

“In Zhang’s view, it would still be crazy and impractical (and illegal) to try to clone a person. Despite the higher efficiency, he notes that Chinese teams used 63 surrogate mothers and 417 eggs to make two monkey clones. Just imagine arranging for dozens of human surrogates and egg donors.

“‘No society could accept this,’ says Zhang.”

Sadly, I think that looking at human rights abuses around the world, there are societies that would accept this. Certainly, there are governments that would do so if they saw advantage in it.

In any case, other researchers are making progress on artificial wombs – a technology which could one day be applied to human beings – thus obviating the requirement for surrogate mothers.

Though we’re not there yet, we are closer to the point at which human cloning becomes a practical, though not ethical, option.

Time to start thinking about the implications again.

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Peter Franklin is Associate Editor of UnHerd. He was previously a policy advisor and speechwriter on environmental and social issues.

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