Can you breed humans with animals

Izpisua Belmonte says that the team does not intend to implant any hybrid embryos into monkeys. Rather, the goal is to better understand how cells of different species communicate with each other in the embryo during its early growth phase. Attempts at growing human—mouse hybrids are still preliminary and chimaeras need to be more effective and healthier before they can be useful. Scientists suspect that such hybrids might have trouble thriving because the two species are evolutionarily distant, so the cells communicate through different means.

But observing cellular cross-talk in monkey—human embryo chimaeras — which involve two more closely related species — could suggest ways to improve the viability of future human—mouse models, Izpisua Belmonte says. Hybrid zoo: Introducing pig—human embryos and a rat—mouse.

In the study, researchers fertilized eggs extracted from cynomolgus monkeys Macaca fascicularis and grew them in culture. Six days after fertilization, the team injected embryos with human extended pluripotent stem cells, which can grow into a range of cell types inside and outside an embryo.

The embryos each developed unique combinations of human and monkey cells and deteriorated at varying rates: 11 days after fertilization, 91 were alive; this dropped to 12 embryos at day 17 and 3 embryos at day She noted that this team, like others in the past, was not able to control which cells developed into which tissues — a key step to master before such models can be used. Martinez Arias was not convinced by the results.

Combining human cells with closely related primate embryos prompts questions about the status and identity of the resulting hybrids. He says this team was thorough in following existing guidelines. These will address non-human-primate and human chimaeras, says Hyun, who is leading an ISSCR committee discussing chimaeras. Many countries — including the United States , the United Kingdom and Japan — have at points limited research on chimaeras involving human cells. Genetic analysis suggests there may have been a long period of cross-breeding between early ancestors of the humans and chimpanzees, before they finally split into the Homo and Pan chimp genera around six million years ago.

But today, although humans and chimpanzees share 99 per cent of the DNA sequences that code for proteins, that DNA is packaged differently into the chromosomes.

The human chromosome number two is actually two ape chromosomes joined end-to-end, and nine other chromosomes have inverted sequences of genes compared with their equivalents in chimps. Would we be less likely to eat pigs if we were using them to grow human organs? Credit: iStock. We eat pigs, not humans. Would you still enjoy bacon if it came from the pig who had nursed your liver for the past six months? More powerfully, the prospect of pig-humans also confuses the moral compass.

Biologically merging pigs with humans reminds us of our shared similarities, something that we mostly try to forget when savouring the smell of frying bacon. We tend to maintain clear boundaries between those animals we eat and those we do not , as this helps to resolve the sense of discomfort that we might otherwise feel about using animals for food.

It was this very confusion of boundaries that led to outrage over the prospect of horse meat in burgers during the horse meat scandal ; horses are perceived as pets or companions, not food. If confusing pets with animals we eat creates discontent, then confusing those same meat-animals with our own kind is sure to create moral and gustatory hesitation.

Beyond baffling our palate, it also confounds our understanding of whether it is an animal from whom we are harvesting our next-generation organs, or some kind of sub-human entity. In the end, while mythical hybrid beasts may have caused alarm for the Greeks, it would seem that our own objection to growing our next heart in the breast of a pig has more to do with existential angst and a disruption of the moral order.

Whether or not we should use animals for these purposes, or for the satisfaction of human needs more broadly, is a topic for another time. NIH officials say there are fewer than a dozen US academic labs researching with animal-human chimeras. One is at Stanford University, where Sean Wu is working to understand how to repair human heart tissue.

Still, Wu says some ethical concerns about human behavior or functions being transplanted into animals are in the realm of science fiction. One way to avoid the consciousness-raising quandary is by deleting bits of DNA that are responsible for the development of certain parts of the human brain before implanting into a lab animal.

The NIH just wants to make sure its standards can keep up.