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An international research team reports in the renowned specialist journal “Cell” that they have succeeded in producing embryos consisting of both human and monkey cells.

These hybrid creatures were able to develop in the Petri dish for more than two weeks and were examined for up to 19 days after fertilization.

A transfer to a surrogate mother did not take place.

The researchers led by the Spanish scientist Juan Carlos Izpisúa Belmonte from the Salk Institute in San Diego studied how human cells interacted with crab monkey cells in the embryo.

They apparently influence each other, report the researchers from the USA, Spain and China participating in the study.

The news of living chimeras made of humans and animals involuntarily creates threatening images in our heads and awakens primal fears.

Such hybrid creatures can already be found as motifs on the oldest sculptures and rock drawings of Homo sapiens.

Is that ethically even allowed?

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In southern Germany, for example, a mammoth tusk was found around 30,000 years old and carved into it by a person with a lion's head.

Modern science has catapulted these primeval human fantasies into the realm of what is technically possible.

The research at the Salk Institute immediately provokes two questions: What is this good for?

And is that even allowed ethically and legally?

The question of legality is easy to answer.

"The current experiments on animal-human hybrid beings are being carried out with animal embryos and human induced pluripotent (all-rounder) stem cells," explains Professor Rüdiger Behr from the Leibniz Institute for Primate Research in Göttingen.

"The induced pluripotent stem cells are made from human skin cells, for example, and are neither covered by the Embryo Protection Act nor the Stem Cell Act, which regulates the handling of all-rounder stem cells obtained from human embryos," said Behr.

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The experiments with chimeras that have now been published are therefore also generally allowed in Germany, says Professor Jochen Taupitz, director of the Institute for German, European and International Medical Law, Health Law and Biomedicine.

Nonetheless, Taupitz urges caution, because the "human stem cells introduced into the monkey embryo could pass their information on to the monkeys' germ line", and refers to a statement by the German Ethics Council, which had already demanded in 2011 "that attempts to produce transgenic great apes because of close relatives to humans should be prohibited ”.

But as long as such hybrid creatures only exist in the Petri dish for two to three weeks and are not carried to death by a surrogate mother, there is no danger that viable chimeras will populate our planet.

Without going this is not the intention of the experiments.

According to the researchers, the research work with hybrid beings should lay the foundation for a medical revolution.

The long-term goal is to obtain human organs for transplantation.

Given the great shortage of donor organs, the tempting possibility is that organs made from human cells will first mature in animals before they can then save a person's life.

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New regenerative therapies based on human tissue grown in animals are also conceivable.

The researchers have agreed for years that the most suitable organ incubator would be the pig - because it is physiologically similar to humans in many respects and the size of the organs of pigs and humans are quite similar.

So why are the researchers not experimenting with pigs right away, but with great apes?

So far, no scientist has succeeded in keeping chimeric embryos from cells of mice and humans or pigs and humans alive in the laboratory.

"This study represents a breakthrough in chimera research," comments Professor Stefan Schlatt, Director of the Center for Reproductive Medicine and Andrology at the University Hospital in Münster.

The target are human organs from pigs

For the first time, the interaction between human and animal cells could be studied.

The fact that this was successful with long-tailed macaques is very likely to be related to the closer evolutionary relationship with humans.

The researchers hope that the new knowledge about the interaction of the cells of the chimeric embryos can ultimately be used for the development of viable embryochimeras from human and pig cells.

Research therefore has a clear application-oriented goal, but it is also basic research.

“Basic research on chimeras has already yielded a lot of new knowledge in recent years and is helping to better understand the formation of tissues and organs during early embryogenesis,” says Schlatt.

From the new findings of the researchers working with Izpisúa Belmonte, "new strategies can possibly be derived how one can also improve the survival of human cells in pigs or other animal species in order to then breed human kidneys and pancreases in pigs, for example," Behr notes .

Even if the current experiments with chimeras are ethically harmless from the US, Chinese, Spanish and also German point of view, the question arises in the future as to how the carrying out of animals with human organs should be assessed.

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Professor Michael Coors, head of the Institute for Social Ethics at the Ethics Center of the University of Zurich, points out that it is still largely unclear whether and to what extent there is a risk “that human genetic material may also penetrate the germ line of chimeras or theirs Affects brain development ”.

The study that has now been published creates the first basis for further research into these risks.

Transgenic monkeys with better memories

A study published in March 2021 in the Chinese science journal “National Science Review” shows that human genes can actually change the monkey brain and apparently even stimulate it to perform better.

Bing Su's researchers from the Institute of Zoology in Kunming had smuggled the human MCPH1 gene into eleven rhesus monkey embryos using a virus vector.

The researchers report that the brains of these transgenic monkeys develop more slowly than that of their untreated conspecifics.

But when they were two to three years old, they did significantly better in memory tests.

Your short-term memory has improved.