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30 May 2016

The Reality of Hieronymus Bosch’s Fantastical Creatures

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Has biotechnology made the fantastical creatures painted by Hieronymus Bosch a reality?

Most works by Hieronymus Bosch are populated by fantastical, strange and even monstrous creatures. Meanwhile, emerging biotechnology techniques may also be capable of engendering such “monsters”. Will any of these new biotech animals match those created by the Dutch master? If so, what use might such new creatures serve?

Giants they are; but normal they are not.

In the central panel of The Garden of Earthly Delights, a series of giant birds -giant compared to the size of the nearby humans- appear in the left foreground. And yet these birds seem well proportioned and could hardly be termed “monstrous”. In fact, we can even recognize the specific species: hoopoe, kingfisher, robin, goldfinch and more.

“The Garden of Earthly Delights” (Hieronymus Bosch) 1500-1505. Grisaille, Oil on oak board / Image: Prado Museum

Uncommonly large specimens of a given species, such as horses or cows, sometimes do appear in nature. And they emerge “naturally” rather than intentionally (or at man’s behest). However, the latter stages of the 20th Century saw the emergence of transgenesis, a technique for introducing the growth hormone gene into a given zygote or reproductive cell, normally from a different cell but sometimes the same. The implanted gene has a highly active regulatory region, causing it to be expressed beyond the normal level and thus resulting in a “giant” animal. Man has used this technique to create giant mice, as well as jumbo versions of other species, such as salmon.

A genetically modified salmon behind a conventional Atlantic salmon of the same age (in the foreground). Image: AquaBounty Technologies, Inc.

Initially such giants were created to ascertain whether the transgenesis technique would really work in vertebrates. However, subsequent work sought to capitalize on the attending properties, such as faster growth and leveraging on energy in the case of giant salmon.

The chimeras of the animal world

The works of Hieronymus Bosch are populated with chimeric animals, featuring body parts seemingly taken from different species. Well-known chimeras such as centaurs and griffins are on show, as well as others that can only be found in Bosch’s work, such as the creature with a human body and the head of a bird at the bottom of the right hand panel (in hell) of the Garden of Earthly Delights. Hybrids between different animal species have been seen in nature, and particularly in the world of cattle raising, but there are not many cases in which such hybrids are chimeric, meaning with parts from other species in different regions of the same body. Perhaps the best known examples are the hybrids between tigers, lions and leopards (liger, tigard, jagleop, jaglion, leopon…), created to be exhibited in zoos.

Liger in Novosibirsk zoo (2005)/Credit: Алексей Шилин

Today the idea of a chimera differs from an interspecific hybrid. Specifically, chimeric animals are those that have cells in their bodies from two or more different individuals, be they of different species or the same. Hybrids, meanwhile, have only one cell type, albeit with genetic information from two different species.

One example of a modern day interspecific chimera is the goat-sheep, created by mixing the embryo of a goat with that of a sheep. These chimeras are used to study issues of incompatibility when females from one species are used as “surrogates” for embryos of another species, a very useful technique in the livestock industry. Adding human embryonic cells to animal embryos (normally mice) has been used to research the role that said cells play in the development of various organs, or how they respond to different medical treatments. One particular example of this kind of chimera are the so-called mice avatars, which are injected with tumors from cancer patients to test out potential treatments for humans.

Any kind of organism (including of human species) that has received an organ, tissue or cell transplant from another species might also be considered interspecific chimera. These are known as xenotransplants, and are used mainly to redress a lack of biological material, as in the case of organ transplants for humans.

Intraspecific chimeras

Laboratories have also produced chimeras with cells from different embryos of the same species. These include mice created by mixing the embryos of two different mice. As one of these embryos may also have had a specific gene inactivated, they are called knockout mice for said gene. These can be used for research into the effects a given gene has in the resulting mouse, which is useful for learning about genetic diseases. Creating such chimeras from primates is more complicated, but chimeric monkeys were recently produced by mixing stem cells from a number of embryos. Again, these experiments allow us to understand how organisms closely related with the human species develop, with a view to applying this knowledge in medicine.

Stretching this concept of chimera a little more, even organisms that have undergone intraspecific organ transplants and transfusions might be labeled as such. Recent DNA studies have shown that chimeric organisms can form naturally from the combination of two zygotes -or early stage embryos- of the same species that are produced independently and simultaneously. Such cases have been seen in paternity and maternity disputes. And there may even be some chimerism in women when they become pregnant, caused by the emigration of some masculine cells to the mother. Are cyborgs the chimeras of the future? Such organisms already feature artificial tissues.

Monsters and monstrosities

As well as creatures such as the birds described above, the works of Hieronymus Bosch also feature other truly monstrous giants. Probably his most iconic monster is the giant man-tree, which grabs the viewer’s attention in the right panel (hell) of the piece. We start using the term monstrous in nature when creatures take on truly gigantic proportions, such as giant squid. In modern biology the idea of creating giant pigs through transgenesis, with a view, of course, to enjoying their huge hind legs, failed because the resulting animal was large, but poorly proportioned and suffered from mobility and functional problems. Work is currently underway to engender super-muscly pigs without such difficulties via new genome editing techniques and CRISPR-CAS technology.

Teratogenic animals

Bosch paintings also include teratogenic creatures, meaning those with more or less normal body parts, but located in places that are not their usual positions. One example is the three-headed bird in the foreground on the left panel (paradise) in the Garden of Earthly Delights, or the three-headed reptile surging out of the lagoon behind the figures of God and Adam and Eve on the same panel. Animals like this sometimes appear in nature, perhaps with two heads or extra eyes due to development anomalies associated with genetic or environmental factors. Animals can now be produced with ectopic eyes, for example. These include vinegar flies, drosophila, which as well as their normal two eyes have others elsewhere on their bodies, perhaps also on their heads or even on their legs. The aim is to demonstrate that a correctly manipulated gene is capable of expressing itself and be functional even when displaced from its usual position. All of which is useful for basic research into development and evolution, but can also be handy for addressing medical and developmental problems in humans.

A fragment of “The Garden of Earthly Delights”, in the top left corner of the “hell” panel (right) / Image: Prado Museum

Lastly, the works of Hieronymus Bosch also feature “monstrosities”, such as organs with no bodies (like the two ears split by a knife in the hell panel). Such things obviously do not exist in nature. However, humans are currently creating organs outside of bodies via stem cell cultures. Thus, scientists are creating small liver or kidney tissues, which are useful for basic research into development and can also be used to research treatments for medical conditions, possibly even for transplants in future.


More than 500 years after the death of Hieronymus Bosch, we do not know what inspired him to paint those strange creatures (perhaps traditions and literature, alchemy, astrology…), nor what his intentions were (mere fun, allegory of sin, to provoke a disinclination toward sin, in defense of a heretical way of living…). But now, as always, his works elicit admiration and fascination, and sometimes fear and horror.

We might also consider his paintings prophetic in a certain biological sense. In fact, scientists creating organisms in the laboratory, similar to those that Bosch brought to life in his paintings, only serves to support the arguments of writers like John Berger1, who holds that Hieronymus Bosch, in works such as The Garden of Earthly Delights, predicted our modern world: globalized, no clear horizons and, as we have seen, artificial and chimeric, due to the emergence of new kinds of animals and new biotechnological constructs.


Manuel Ruiz Rejón

Granada University, Autonomous University of Madrid

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