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TSS EXCLUSIVE: Is cloning – a relatively, dormant scientific field – due for a resurgence?

by A’liya Spinner


The word “cloning” typically brings to mind science-fiction dystopias and far-off futures, but “cloning” is a naturally-occurring process as old as the idea of nature itself. Single-celled microbes, the first known instance of life on planet Earth, appeared in warm, primordial soup about 3.7 billion years ago. These ancient lifeforms replicated themselves by self-cloning— an asexual form of reproduction still performed by the descendants of those microbes: prokaryotes (single-cellular organisms like bacteria) and the individual cells in the bodies of much larger and complex lifeforms like plants, fungi, and animals— including human beings.


Cloning on a small, single-cellular scale is happening constantly inside our bodies. It happens in laboratories, too; in the 1980s, American biochemist Kary Mullis invented a process known as Polymerase Chain Reaction (PCR), which allows scientists to rapidly duplicate segments of DNA, producing billions of copies of the desired sequence. Cloning through PCR revolutionized forensics and genetic testing, turning small samples into large cultures for study and identification.

但当提到克隆时,人们想到的并不只是发生在科幻小说中的细胞复制或PCR:而是生殖性克隆。生殖性克隆是将一个基因复制到先前存在的多细胞有机体上,或者创造一个生物的精确副本。类似的事情也发生在自然界:例如,任何能生同卵双胞胎的物种,都有机会产生自然发生的多细胞“克隆体”。但是,在实验室里应用这个未来主义的想法的历史比大多数人所知道的要丰富得多。人工生殖克隆可追溯到20世纪,当时德国胚胎学家汉斯·斯佩曼(Hans Spemann)将蝾螈胚胎“变为孪生”(split),并因此获得诺贝尔奖。克隆蝌蚪的罗伯特·布里格斯和托马斯·金于1952年发明了第二种克隆方法,称为“细胞核移植”,即将遗传密码从细胞转移到未受精的胚胎。这一过程在1958年被复制到用肠细胞克隆青蛙,之后,在1996年,被用于一只名叫多利的人尽皆知的母羊。

But when cloning is mentioned, it isn’t cellular replication or PCR that people envision taking place in a science-fiction setting: it’s reproductive cloning. Reproductive cloning is the production of a genetic duplicate to a preexisting, multicellular organism, or creating an exact copy of a living thing. Something similar happens in nature: any species that can give birth to identical twins, for instance, has the chance to produce naturally-occuring, multicellular “clones”. But even the laboratory application of this futuristic-sounding idea has a much richer history than most people know. Artificial reproductive cloning dates back to the 1900s, when German embryologist Hans Spemann “twinned”, or split, a salamander embryo, for which he won a Nobel Prize. A second method of cloning known as “nuclear transfer”, wherein genetic code is transferred from a cell to an unfertilized embryo, was developed in 1952 by Robert Briggs and Thomas J. King, who cloned tadpoles. This process was replicated to clone frogs using intestinal cells in 1958, and then, perhaps most famously, a female sheep named Dolly in 1996.


Dolly proved what was previously thought to be impossible: adult mammals can be cloned, including, perhaps, human beings. But rather than exploring this development or continuing to build on over a hundred years of progress, reproductive cloning seemed to come to a standstill, explored only in speculative fiction despite being a tried and proven process. But why was that? Why did Dolly the sheep slow the progress of an entire emergent scientific field, and might it someday resume?

It’s Harder For Humans


The first reason for this stagnation lies in the science of cloning itself— cloning humans is much more difficult than salamanders and frogs. Unknown to many, the creation of Dolly was actually a happy accident, born from the control group of adult cells, while the experiment itself focused on embryonic and fetal cells. And just because Dolly was born, accident or not, does not mean that her success was easily replicable— she was the only viable birth throughout the course of the experiment, which involved 277 cell fusions, 29 created embryos, and 13 implantations into surrogate mothers. Attempts to clone sheep that followed Dolly produced lambs with life-threatening diseases or extreme disabilities, a common side effect to the imperfections of the cloning method. Ian Wilmut, one of Dolly’s creators and the scientist who shortly thereafter produced these deficient copies, called it a “distressing” sight and discouraged experimentation with human embryos due to likelihood of abnormal births and lost pregnancies.


That may not always be the case in the future, however. Since the triumph of the 2018 macaque twins, the field of mammalian cloning has declared several important breakthroughs. In summer of 2020, the cause for oversized placentas in SCNT-cloned mammals was discovered after almost twenty years of research and mystery. Oversized placentas cause myriad issues during fetal development, but after correcting for this (the culprit was an overexpression of microRNA in clone genome) the number of successful pregnancies and births doubled.


Another recent breakthrough was discovered by Dr. Yi Zhang, a stem-cell researcher at Boston Children’s Hospital; adult cells, from which clones are derived, have already specialized to a specific purpose in the body (such as being a part of the skin or liver), and have thus “shut down” certain genes. Implantation into an egg can reactivate many of these genes, but there are only a few hours to do so before the embryo begins developing with many crucial genes still unavailable, resulting in the demise of the clone. Several years ago, however, Zhang discovered a chemical that, when added to the egg, helps release the blocked genes much faster. Tested on mice, the chemically-modified eggs succeeded 10% of the time, compared to a dismal 1% rate of unaltered trials. A few years later, Zhang’s team tested the eggs of volunteer human women; without the chemical, no eggs successfully began development, whereas a quarter of those with the chemical did. Zhang’s team never implanted the embryos in hopes of making human babies; their goal was to develop ways to clone stem cells from adults in need, creating genetically identical tissues for sick people at a reasonable price. But even though he isn’t planning on using his breakthrough for human cloning doesn’t mean another entrepreneurial scientist won’t.


With the recent advances in mammal and primate cloning technology, it’s more than possible that the issue of human cloning will be brought back to the forefront of science and public debate. Perhaps the quiet years of the past few decades were truly necessary to advance techniques, discoveries, and technology to the level where reproductive human cloning was feasible. If this is true, we may soon see a much stronger demand for human clones evolving from the pet-cloning market; but there’s another side to the story of reproductive cloning beyond just the science— that of ethics, morality, and fierce debate.

Social Stalemate


For some, the idea of cloning occupies very little space or worry in their mind. For others— especially those scientists actively involved in the duplication of living organisms— human cloning is a contentious, concerning, and touchy subject. Many researchers engaged in the study of cloning— including Dr. Yi Zhang— vocally discourage the use of reproductive cloning to create living human beings. “No society could accept this,” Zhang has said, commenting on the extreme cost of failed embryos and faulty pregnancies that comes with mammalian cloning. Zhang intends only to use cloning to produce embryonic stem cells with the same genetic code as their donors, a process that, only a few years after its discovery, may be becoming obsolete due to the rising success of induced pluripotent cells— cells derived from an adult’s cells that have been reverted back into an unspecialized state in a laboratory setting, making them as versatile as embryonic stem cells. Given that induced pluripotent cells are less complicated to create than cloned embryos, they will likely replace the medical need for embryonic stem cells in the coming years, diminishing the need for cloned human embryos.


But what about cloned humans? Will we ever see children born who are genetic clones of a deceased loved one, or the artificially-created successor to a brilliant scientist or world leader? Here, most of all, is where ethic and moral dilemmas seem to take place. To some— especially prominent and staunchly conservative religious groups like the All American Life League— all forms of cloning human tissue, even embryonic cloning, should be banned. A less severe Evangelical perspective discourages the creation of human clones for fear that it could lead to the commodification of human life, an opinion shared by most major religious groups, especially Muslim ethicists and civil leaders, to whom human cloning is both frivolous and an infringement on the supremacy of God.


While offense or disrespect to a higher power is consistent with and principal to the spiritual perspective surrounding cloning, their secondary arguments— especially regarding the frivolous or irresponsible nature of copying humans— are shared with the secular community. Simply put, most people, especially those scientists working on advancements that could potentially be applicable to the creation of living, human copies, don’t believe cloning is worth it. Despite recent progress in improving feta; viability, implanting cloned embryos can still be incredibly dangerous for both the parent and the child, and the end result— even in the case of a successful pregnancy— will not be an exact replica of the “original”; the personality, talent, and behavior of a person is dependent not only on their genetic makeup, but also on the environment in which they’re raised, the interactions and relationships they forge throughout life, and the unique experiences they undergo.


Today, most psychologists agree that genetic and environmental factors work together to turn us into who we are, and cannot be easily separated; therefore, desirable personality traits or talents cannot be guaranteed in a clone. Grieving parents wanting to perfectly replicate their lost child or families hoping to hedge their bets for successful progeny by raising the clone of an acclaimed author or Nobel Prize winning chemist are unlikely to get what they expect, but rather a new person— with their own aspirations, behaviors, and identity— that is identical to the original in genetic makeup only. It’s easy to see how the unrealistic (and, eventually, disappointed) expectations of those who might choose to pursue cloning will lead to the commodification of human existence and individuality, as well as a lower quality of life for clones in a society where they will likely be ostracized. Ultimately, regardless of religious affiliation or familiarity with the intricacies of cloning, it seems as though most people do not see cloning as an ethical or viable application of modern scientific progress.

Will Cloning Ever Become Common?


Movies like Jurassic Park and Gattaca imply that humanity is doomed to use scientific advancements irresponsibly, but is that really the case? Looking at the state of the world now, it seems unlikely that the thirty-year stagnation of human cloning is going to end anytime soon, let alone begin to develop at an uncontrollable pace. As technology progresses, some countries are taking preemptive legislative action to ban cloning. Over thirty countries prohibit all forms of cloning and fifteen countries ban reproductive cloning but allow therapeutic (embryonic) cloning, although many, including the United States, have yet to pass federal laws outlining what research or practices may or may not be conducted in private laboratories. Despite this, many American politicians (and even prior presidents) have expressed support for a global and universal ban on all forms of cloning of human tissue. Other international organizations, including the United Nations, African Union, and Arab Leagues have discussed the issue of a multinational treaty, and may someday collaboratively attempt to pass global legislation, and to hold the world accountable to a common set of ideals.


Although making particular scientific disciplines illegal does not necessarily discourage stubborn scientists from continuing their research (consider Copernicus and Galileo), it does make it significantly more difficult to gain funding and public support, especially for such a resource-heavy and failure-prone field as cloning. Today, even without a global ban on reproductive cloning, the majority of the world is already firmly against the idea of replicating human beings for a variety of reasons that are difficult to dispute; even with the science at the fingertips and the increasingly common practice of creating genetic duplicates of beloved pets and valuable livestock, it’s unlikely that walking, talking clones are ever going to be more than fun— and purely fictional— speculation.