September 2023 marked the passing of British scientist Ian Wilmut, who made headlines two decades earlier when he and his team at Scotland’s Roslin Institute witnessed the live birth of a female lamb—later named “Dolly”—that was genetically identical to an already-existing adult female sheep. Wilmut and his team had transferred the DNA of the adult sheep to Dolly in embryo, thereby accomplishing the process known as “cloning.”
Long the stuff of science fiction—it was the centerpiece of the 1978 film The Boys from Brazil, as well as 1993’s Jurassic Park—cloning was not unknown to scientists when Dolly was born in 1996. But her birth was nevertheless notable as the first successful artificial creation of an infant mammal from the cell of a live adult. Given the high degree of similarity among mammals and the potential application of the same technology to human beings, Wilmut’s accomplishment kicked off a firestorm of discussion about the ethics of cloning and whether it resembled “playing God.”
Since Dolly, scientists have successfully cloned far more mammalian species, notably including at least one primate. While cloning is today still primarily a research and development activity, it has begun to enter the commercial sphere, with companies offering animal cloning services for pets, livestock, racehorses, and the like. And while no one has yet created a living human being from the genetic material of another—at least not in a verifiable way—scientists have advocated using similar techniques to create human stem cells for research and therapeutic purposes.
In the United States, the legal reaction to this has been surprisingly muted, at least at the federal level. Although Congress sought to pass legislation restricting cloning in 2001, the measure did not become law, and thus, today the only legal restrictions on cloning are state laws and federal administrative regulations.
Cloning is the process of creating a new living organism from part of another one, with the result that the new and the old are genetically identical. Although cloning as a concept frequently conjures up images of scientists in lab coats, the practice has been around since time immemorial in forms much closer to nature than the modern laboratory. The term “clone” comes from the ancient Greek word for “twig,” a reference to the common botanical practice of burying part of a plant in order to grow a new one of the same kind.
The artificial cloning of animals through modern biotechnology is, of course, more complicated, as scientists require more than fertile soil to bring a new animal into being. The most common technique for this purpose is known as “nuclear transfer,” which involves taking a sample cell from an adult being, removing its nucleus, and then placing the nucleus into an egg cell with its natural nucleus removed. Through electric stimulation, the constructed cell can be prompted to divide and grow into an ordinary embryo, which can then (in the case of mammals) be placed into the uterus of a surrogate where it can implant, develop, and be carried to term through ordinary gestation. This was the technique used to create Dolly the sheep, with her name reminiscent of country singer Dolly Parton and the fact that Dolly’s genes came from a mammary-gland cell of her genetic parent.
Wilmut’s success with sheep has since been replicated in many other mammalian species, such that most types of domesticated animals—e.g., dogs, cats, and horses—can now be reliably cloned. In consequence, commercial animal-cloning services are presently available through companies such as ViaGen Pets and the Korean entity Sooam Biotech, although as of yet they are priced out of reach of the average consumer. Given the widespread success of reproductive cloning in live species, some have wondered whether the same techniques could be used to revive extinct species, as in Jurassic Park. One obstacle, though, is the difficulty of finding an adult woolly mammoth (for example) to serve as the surrogate parent for the cloned animal in utero.
Most artificial cloning of animals, however, is not done to produce live young, but rather to create cells and tissues for scientific research. This is done through the creation and harvesting of stem cells, which exist in the nascent stages of embryotic development and later differentiate into other types as an organism matures. The particular utility of cloned tissues in this regard—as opposed to tissues created through ordinary reproduction—is that their genetic similarity makes them more predictable and hence more useful for some forms of testing.
While the cloning of animals has not given rise to extensive legislation, the possibility of cloning human beings has raised profound concerns. In 1998, two years after Dolly’s birth, the U.S. Food and Drug Administration asserted that its approval would be required for any human reproductive cloning, ostensibly for safety reasons. Three years later, the U.S. House of Representatives voted to ban all forms of human cloning, but the bill did not pass the Senate and hence did not become law. Since then, the issue has not been taken up at the federal level outside of regulatory restrictions on the use of federal funds for scientific research.
In the absence of federal action on human cloning, nearly half of individual U.S. states have stepped up to address the issue in some form. Several states have enacted legislation prohibiting human cloning for any purpose, reproductive or otherwise. Others allow cloned human embryos to be created for research or therapeutic purposes provided that they do not result in live births. These are colloquially (and somewhat crudely) referred to as “clone and kill” laws. Still others address the issue less directly, such as by prohibiting state funding of cloning-related research, or recognizing rights of conscience for health care practitioners to refuse to participate in cloning activity.
While reviving dinosaurs or other extinct species may as yet be a few decades away, other potential applications of cloning are nearer to hand. For one thing, there is no scientific reason why the same techniques available to re-create pets could not also be used to create animals from endangered species in order to preserve them. This would have particular utility, scientists have noted, for animals that have difficulty breeding in captivity, and need only be a temporary measure once sufficient numbers are achieved for ordinary sexual reproduction.
As for humans, although it is true that cloning to create duplicate persons has few advocates, that is hardly the end of the story. Separate from creating whole human beings is the possibility of creating particular cells or tissues from embryonic stem cells. Through the cloning process, such cells can be tailored to a particular organism—i.e., a specific person—such that they will be accepted by the body even without immunosuppression drugs. It is easy to see the potential therapeutic value of such made-to-order cells in the case of, say, a patient suffering from Alzheimer’s or heart disease who requires some form organic or tissue replacement. At present, however, this is merely an area of research, is not yet in medical practice anywhere in the world, and as with human cloning for reproductive purposes, is not without controversy.
