Technical and ethical barriers prevent human clones from being created 25 years after Dolly Schaf

The 25 years that have passed since the birth of Dolly the sheep, the first viable clone of a mammal, is an exemplary lesson in how technology development tends to follow nonlinear and unpredictable paths.

The most obvious element of this unpredictability has to do with the total absence of human clones in the world in 2021, though the ethical debates that followed Dolly’s announcement of her existence have been obsessing about this for a number of years.

At the beginning of this century, the birth of the first cloned baby sometimes seemed just a matter of time, and some personalities with questionable reputations soon announced it.

Such was the case of the American-Cypriot physiologist Panayiotis Zavos, 77, now professor emeritus at the University of Kentucky, and the French religious leader Claude Vorilhon, 74, known as Raël (the sect he founded mixes idiosyncratic interpretations of the Bible with the Belief in extraterrestrials); for reasons of common sense the reader will probably not want to know any more).

Despite the bravery of Zavos and Raël, the ethical objections to the process added to the gigantic technical difficulties and eventually led to a world without genetically copied people.

The main obstacle, which will most likely remain indefinitely, is that it takes hundreds of embryos and dozens of surrogate mothers for a single clone to be born.

This means that large numbers of women are exposed to risky pregnancies that would ultimately produce babies with a high risk of disease and a shortened lifespan.

What happens is that the DNA reprogramming process from the adult state to another “primitive” essential for cloning often works poorly and the cloned individual has a finite life expectancy.

These problems have been greatly reduced when cloning animals such as pigs for veterinary purposes. In such cases, the issue is the mass production of animals with high commercial value.

However, the process is still far from having a significant impact on the market, and copied animals have a significant disadvantage: low genetic variability, which makes them more susceptible to disease, among other things.

For a long time there was talk of therapeutic cloning, a technique in which the cloned embryo is destroyed when it only has a few hundred cells and a few days to live. Then such cells with multivalent capabilities would be used to grow tissues and organs that are tailored for transplantation. Since they carry the same genetic material as the cloned individual, there is no risk of rejection.

Also due to ethical issues (after all, it would be necessary to destroy a human embryo) and technical difficulties (there would still be a large number of egg cells to be obtained from donors), therapeutic cloning ultimately inspired another approach, which is much more widely used today.

This involves the formation of so-called iPS cells (“induced pluripotent” in the English acronym). By activating certain key genes, the researchers learned how to return adult cells – obtained through a skin biopsy, for example – to a study very similar to the embryonic one with the same versatility or “pluripotency” – hence the name.

The approach has yet to lead to treatments, but iPS cells have proven very useful for organ development studies and drug testing, among other things.

The irony is that without the knowledge of adult DNA reprogramming that began to pile up thanks to working with various forms of cloning, it would have been much more difficult to reach iPS cells. From this point of view, the clones acted as leaders, not as ends in themselves.

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