To some, the two macaques playing in their incubator represent a big leap for science that could bring huge benefit to us all. To others, they are just the latest example of scientists going too far.

Either way, Zhong Zhong and Hua Hua are attracting global attention because they are clones - perfect genetic copies of each other, created artificially in a lab in China.

As primates, they have rekindled concern about how long it will be before scientists start cloning another type of primate: us.

For those who see this as a sci-fi nightmare, the team has bad news. “The barrier of cloning primate species is now overcome”, declared Dr Mu-ming Poo, co-author of the research and a director at the Chinese Academy of Science.

Happily, Dr Poo and his colleagues have stressed they have no interest in cloning humans.

They insist their goal is something far more wholesome: to create batches of genetically identical monkeys for use in the quest for treatments for human disorders like Alzheimer’s Disease.

That hasn’t assuaged fears that less scrupulous researchers will soon be mass-producing mad dictators, in a real-life version of The Boys from Brazil.

In truth, the hoopla over Zhong Zhong and Hua Hua is something of a joke, like their names. (The official name for China is Zhonghua – get it?)

To start with, they are not the first cloned primates. Those emerged back in the late 1990s using a technique which mimicked the way nature creates identical twins: a single embryo is simply split in two at a very early stage, and each half allowed to develop.

What makes the Chinese macaques scientifically notable is that they were created by a method more likely to lead to mass-produced clones suitable for lab tests.

Known as Somatic Cell Nuclear Transfer (SCNT), this first made headlines in 1997, when British scientists unveiled its first success: Dolly the Sheep, the first mammal to be cloned using cells from a fully-grown adult.

Unlike those in an embryo, the genetic instructions in such cells are easy to manipulate and easy to access. (Dolly’s were taken from her mother’s udder.)

The problem is persuading them to produce a clone of their original owner.

The cells in our bodies have all taken up specialist roles, so they must first be returned to their original state, able to take on any job.

Then the genetic instructions must be put into a cell capable of sustaining pregnancy that ends with the birth of the clone.

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The British team discovered ways of getting cells to return to being generalists, and ways of using their genetic instructions with an egg cell from another sheep, whose own instructions have been removed.

The combination was implanted back into a sheep and five months later, Dolly was born – a perfect genetic copy of her mother.

The breakthrough was hailed as the dawn of a new era in medicine. The researchers themselves talked of cloned animals genetically programmed to produce human proteins – like blood-clotting factors for treating haemophilia.

But along with fears of human clones came concern about the cloning process itself.

It emerged that Dolly was the product of hundreds of attempts to fuse the genetic instructions into an egg cell, followed by dozens of failed pregnancies.

Quite apart from the yuk factor, it was clear that SCNT would have to be far more efficient if cloning were to become big business.

That is where Dr Poo and his colleagues come in. Using chemicals and a deactivated virus to do the critical transfer of genetic instructions, they’ve found ways of boosting the hit-rate.

Yet despite all the high-fives, it remains desperately low.

When the team tried creating clones using cells from an adult macaque, they ended up with two live animals out of over 180 attempts and both died soon afterwards.

They did better by switching to cells from embryos, but it still took 79 cloned embryos implanted into 21 monkeys to end up with Zhong Zhong and Hua Hua.

As breakthroughs go, this one has failed to impress even some scientists whose research might benefit. “The numbers are too low to make many conclusions, except that it remains a very inefficient and hazardous procedure”, said Professor Robin Lovell-Badge, an expert of embryology at the Francis Crick Institute, London. “[I]t would have been far simpler to just split a normal early embryo into two”.

Still, there was plenty of upbeat talk about the ultimate potential of cloning, once these wrinkles have been ironed out.

Even using current techniques, scientists have been able to clone top-quality cattle to boost meat quality, re-create a dead cat, and think it could bring extinct species back to life.

Last year, researchers in Dubai created the first cloned Bactrian camel – a step towards preserving this critically endangered species.

But it is the medical applications that still arouse most excitement. Researchers talk of the benefits of testing new therapies on cloned animals, free of the genetic variability that can mask effectiveness. Being closer to humans than mice, cloned primates are of special interest.

Yet such soaring claims have been made countless times before. The reality is that genes have failed to live up to their billing as the key to the ultimate medicine cupboard.

Their influence on major diseases has proved far weaker than expected, and “gene therapy” remains a niche area of medicine.

As for cloning, the creators of Dolly the Sheep never did create those flocks of protein-making animals. The amounts they produced simply weren’t viable.

Cloned animals may yet prove useful as test-beds for new therapies for Alzheimer’s and the like.

What we really need, however, are better ideas to test in the first place. And they remain as elusive as cloned unicorns.

Robert Matthews is Visiting Professor of Science at Aston University, Birmingham, UK