Cloning. IVF. Stem cells. Centuries of studying the egg, the cell, and the embryo have led to amazing advances that benefit humankind. Through the science of reproduction, people have accomplished noble goals, such as overcoming infertility, as well as mundane conveniences, such as better beef. These ten oddities reproductive science showcase the weird, wild, and wonderful ways researchers have bent nature to their will.
10 Baby Hair Lassos And Salamanders
Scientist Hans Spemann discovered that his usual instruments slipped off early‑stage salamander embryos – they were simply too slick. While cradling his nine‑month‑old daughter, he had a flash of inspiration: snip a lock of her hair and try again. Using tiny nooses fashioned from his baby’s hair, Spemann returned to the lab and began experimenting.
In one early trial, he split the embryos with the hair‑lassos. Defying the prevailing theories of the era, the result was a pair of independent, fully formed salamanders – essentially artificial twins. Later, he constricted a cell into a dumbbell shape, nudging the nucleus into one compartment. When he loosened the hair‑noose, the nucleus slipped back into the previously nucleus‑free half, which then divided, effectively cloning the developed side of the embryo.
The outcomes varied with the exact placement of the cut and the degree of constriction. A cut through one region produced identical twins, while a cut elsewhere yielded a half‑developed embryo paired with a clump of blood and gut tissue. A gentle constriction generated a two‑headed salamander, whose two heads fought over the same food, earning Spemann the nickname “two egotisms in the place of one.” He kept these grotesque specimens for further research.
9 Urine Clones
Dolly the sheep emerged from nuclear transfer, a technique where a nucleus from an adult cell is inserted into an enucleated egg and then implanted into a surrogate. While nuclear transfer holds promise for preserving endangered species, harvesting donor cells can inadvertently harm the animal. Researchers at the University of Yamanashi proposed a painless alternative: harvesting cells from urine.
Urine contains a variety of cells, such as those shed from the bladder and kidney, which can be cultured after collection. Although urine’s toxic components were thought to jeopardize cell viability and nuclear integrity, the team demonstrated that urine‑derived cells could survive to early embryonic stages and be transferred to surrogates for further development.
These urine‑derived clones progressed to maturity and, when bred, produced offspring, indicating that the cells retained full reproductive capacity. Nevertheless, collecting sufficient urine‑derived cells from wild animals in pristine conditions remains a logistical hurdle.
8 IVF In History
In‑vitro fertilization (IVF) gives infertile couples a chance to bypass their bodies’ limitations and conceive children. Gametes are combined in a tiny glass dish to form a zygote, which, after reaching the early‑embryo stage, is re‑implanted into a woman’s uterus. Today, IVF is a routine, albeit costly, procedure responsible for millions of births worldwide.
Decades ago, IVF was shrouded in controversy and deemed both unethical and impossible. The pioneers behind the first IVF baby faced accusations of “playing God.” Early protocols were labor‑intensive and secretive; women spent two to three weeks as in‑patients in portable clinic buildings, collecting all their urine for hormone monitoring and providing samples every three hours, even at night.
Egg retrieval once required a form of keyhole surgery involving small incisions. Modern techniques now use mild sedation, allowing clinicians to extract eggs by gently aspirating them with a needle under ultrasound guidance—a process that takes roughly half an hour.
7 Cloning Abnormalities
Dolly the sheep, celebrated as the first adult‑mammal clone, was the sole survivor among 277 clones produced by her creators. While reproductive failures—stillbirths and birth defects—are common across species, cloning has a notorious track record of complications.
Some cloned fetuses develop abnormalities, the most striking being “large offspring syndrome,” where calves or lambs are 30‑40 % larger than normal, leading to difficult deliveries. Other health issues include organ defects affecting the brain, heart, and liver. Cloned animals that survive birth often face health challenges for the first few months, but by six months they become indistinguishable from naturally bred counterparts in appearance and blood parameters.
These welfare concerns prompted the European Parliament to ban farm‑animal cloning in 2015, though cloning of cattle continues in the United States, with hundreds of clones produced annually.
6 Resurrection From A Steak
Identifying top‑quality beef without slaughtering the animal is a paradox. Researchers at West Texas A&M University solved this by cloning directly from premium steaks. Only about three in 10,000 carcasses yield the coveted rib‑eye steak with abundant intramuscular fat but minimal undesirable back fat.
When a scientist spotted two such rare rib‑eyes in quick succession, he contacted Dean Hawkins, head of the university’s animal‑science department. Using a tiny sample of meat, they extracted cells, harvested DNA, and inserted it into enucleated cow eggs. One steak originated from a castrated bull, the other from a cow that had never calved.
Four clones resulted: “Alpha” from the bull’s steak and three “Gamma” clones from the cow’s steak. The team bred these clones, producing 13 calves—the first bovine offspring derived from cloned carcasses. Seven of those offspring were later slaughtered, and their carcasses received grades far above industry averages, demonstrating the potential of steak‑based cloning to propagate superior beef genetics.
5 ET And Cows
In the 1970s, American ranchers began pushing reproductive boundaries with embryo transfer (ET). While a cow naturally carries a single embryo, ET enables a donor cow to produce six or seven viable embryos per cycle, with some cases yielding 80‑90 embryos.
Embryos are harvested through thin tubes and implanted into surrogate cows for gestation. This technique allows farmers to generate dozens of calves annually from elite genetics without the donor cows ever giving birth themselves.
However, ET carries a risk of inbreeding if a herd relies heavily on a single donor line, potentially reducing genetic diversity and increasing disease susceptibility. Paradoxically, the USDA maintains a repository of embryos from diverse livestock breeds at Fort Collins, Colorado, helping preserve genetic variation.
4 Artificial Twinning
Cloning can be as natural as the split of a fertilized egg into identical twins. Artificial twinning involves deliberately separating an early‑stage embryo to produce genetically identical individuals. This method has been extensively applied to cattle, yielding thousands of cloned calves.
The first artificial twinning experiment was performed by Hans Driesch in 1885, who shook a container holding a two‑cell sea‑urchin embryo, separating the cells, which then developed into healthy larvae. In 1902, Hans Spemann replicated the technique in vertebrates using a baby‑hair noose to split salamander embryos.
In 2000, a rhesus monkey named Tetra became the first primate cloned via artificial twinning. Researchers split an eight‑cell embryo into four two‑cell pieces, creating four embryos. After generating 368 embryos from 107 split embryos, only one surrogate mother carried a successful pregnancy, resulting in Tetra’s birth.
3 Embryo Screening
Preimplantation genetic diagnosis (PGD) helps IVF couples avoid transmitting disease‑causing mutations to their children. PGD involves extracting one or a few cells from a developing embryo and analyzing their DNA and chromosomes. Embryos that fail the test are typically discarded.
China’s fertility clinics have exploded in size; the largest recorded 41,000 IVF cycles in 2016—about a quarter of the United States’ annual total. PGD usage is projected to grow 60‑70 % annually, potentially matching U.S. per‑capita rates in the near future.
While PGD promises to reduce genetic disorders, it raises ethical concerns: some argue it devalues lives of individuals with disabilities, and the technology could widen socioeconomic gaps as affluent families gain access to “designer” traits. In China, the focus remains on medical benefits, though some families request screening for traits like alcohol metabolism, which the industry officially declines.
2 Artificial Embryos
Scientists at the University of Cambridge reported the creation of an artificial mouse embryo using two stem‑cell types: embryonic stem cells and trophoblast‑like stem cells that normally form the placenta. By combining these cells on a three‑dimensional scaffold that mimics the natural extracellular matrix, they guided development.
Four and a half days after seeding, the cell aggregate resembled a normal mouse embryo, offering a new platform to study early developmental events without using actual embryos. Lead author Magdalena Zernicka‑Goetz explained that this method could illuminate why development sometimes goes awry.
The breakthrough also stirs ethical debate. Current regulations allow only the use of discarded human embryos, which must be destroyed within 14 days post‑fertilization. Artificial embryos could challenge existing boundaries, prompting discussions about the definition of an embryo.
1 The Tale Of The Mouse Princess
In 2004, researchers at Tokyo University of Agriculture achieved a fairy‑tale feat: a mouse born without a father. While mammalian eggs can be induced to divide, unfertilized embryos usually perish because of imprinting errors—genes that are turned on or off during gamete formation.
The team sidestepped this by fusing an immature, non‑imprinted egg with a mature one. The immature egg came from a genetically engineered mouse lacking specific imprinting genes, while the mature egg supplied the necessary genetic material. This fusion produced a viable embryo.
Out of 457 attempted fusions, 371 progressed to the early‑cell stage suitable for implantation. Only ten pups were born alive, and just one survived to adulthood. This survivor, named Kaguya after a Japanese folk‑tale princess discovered in a bamboo stalk, embodied the success of the experiment.
Scientists caution that applying this technique to humans is premature due to its labor‑intensive nature, high failure rate, and the ethical quagmire of genetically altering human eggs. Nonetheless, the story highlights the astonishing possibilities at the edge of reproductive science.