In February 1997 There was one of those scientific news that went around the world in a few hours and sparked numerous debates and controversies alike. Scottish researchers showed the world that they had been able to clone a sheep, which they named Dollyan ironic reference to the American country singer Dolly Parton and to the origin of that animal. They had been able to obtain a sheep from a single-cell embryo reconstructed with the nucleus of a cell from the mammary gland of another sheep. Dolly was a clone of that sheep that had provided those cells.
The Animal cloning had been obtained in frogs in the 50s and 60s of the last centurybut until Dolly’s birth, mammals seemed to resist being cloned. Naturally, that first animal cloned from adult cells launched a race to replicate cloning experiments in other species. Starting in 1997 and in the following years, different research groups managed to clone cows, goats, pigs, horses, rats, mice, rabbits, ferrets… and, of course, it was assumed that, if it was possible to clone all these species, Why not try it with human beings?
An ethical question
It is not the same to carry out experiments with animals as with people. Both processes are extraordinarily regulated, but involving humans in experiments requires exquisite justification and additional evaluation of benefits and risks. Furthermore, it requires a ethical reflectionbased on respect for the dignity that all human beings deserve, about whether it is really necessary to undertake the experiment.
Ethics helps us to elucidate the morality of an experiment, whether an experimental proposal is good or bad, whether or not it is appropriate, according to the values that we have agreed upon in our society. Ethics also helps us answer the important question: Why do you want to do that experiment? And if we don’t have a very good answer for it, it’s time to agree that perhaps the most appropriate thing to do is not to approach this experiment.
1% efficiency
The imagination is free. In 1997 it seemed evident in the minds of many people that cloning a human being was something that was going to happen, whether we wanted it or not. That someone would approach that experiment, with deep ethical connotations. However, scientific and technical reality prevailed and we soon understood that each species required an adaptation of the cloning protocols and that Cloning a primate, like us, was neither obvious nor automatic.
Actually, we had towait 21 years for a Chinese research team to tackle the cloning of a crab-eating macaquethe first non-human primate to be cloned. Reported in 2018, the experiment showed a very low, very poor efficiency, similar to that obtained with Dolly the sheep, less than or equal to 1%.
This means that it was necessary to reconstruct more than 100 macaque embryos and transfer them to macaques to be gestated so that only one of them would reach term and give rise to a cloned macaque: technically possible but scientifically an insurmountable challenge, ethically unjustifiable, impossible to transfer to human beings. The very low efficiency of the process was confirmed six years later, in 2024, when the same team cloned another species of primate, the Rhesus monkey, with similar results and efficiencies.
Experiments without medical justification
Beyond the low efficiency of the process, what is really relevant is once again asking why we would want to clone a human being. And certainly there is no obvious medical need nor any reason that answers that question and justifies the experiment.
Today we know pluripotent embryonic stem cells, inducible pluripotent cells or CRISPR gene editing tools. All of these techniques allow us to resolve issues that initially could only be solved by cloning. This technique, therefore, is currently obsolete and if it is still in use it is mainly because it is the one that allows the most efficient generation of animal models with genetic modifications, such as pigs used in xenotransplantations.
Not all experiments that scientists imagine are technically possible or ethically approved. It is important to know that all experiments in biomedicine are strictly regulated and must be adequately justified and comply with current regulations and legislation so that they can be addressed. Furthermore, any experiment that involves the participation of animals or people requires additional evaluation carried out by the ethics committees, units that review compliance with the law and determine whether or not it can be carried out.
Lluis Montoliu He is a CSIC researcher at the National Center for Biotechnology and at the Rare Diseases Network Biomedical Research Center (CIBERER-ISCIII). He is also the author of the book Not everything goes. What is a scientist doing talking about ethics? (Next Door Publishers, 2024), which illustrates that not all experiments are possible if they do not have favorable ethical justification and evaluation.
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