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Scientists comment on a press release from Colossal Biosciences announcing that chicks have been hatched from an artificial egg system.
New comments from our friends at SMC Spain:
Carles Lalueza-Fox, Director of the Museum of Natural Sciences of Barcelona and specialist in DNA recovery techniques in remains from the past, said:
“The private company Colossal has succeeded in developing an artificial egg, something for which there are no comparable precedents. The most significant breakthrough lies in the permeability of the membrane, which allows gases (oxygen and carbon dioxide) to pass through. Colossal aims to bring back an extinct New Zealand bird, the moa, but its eggs were 80 times larger than those of chickens and about eight times larger than those of the emu; some species of moa stood over three and a half metres tall and could weigh up to 250 kilograms. This means they could not use any modern bird as a surrogate mother, which is why they have opted to develop their own artificial incubation system technology. The most practical approach will likely be to use hens as incubators in the early stages of development and then transfer the embryos to artificial eggs, which can be sized as required. This scaling up to a large-sized embryo will likely require further research to ensure the system is scalable.
“Naturally, it could be used to de-extinct other birds, such as the Carolina parakeet, whose genome I first sequenced six years ago. At that time, the difficulty of manipulating bird genes due to their oviparous strategy ruled them out entirely for any de-extinction endeavour, and, in fact, birds have never been successfully cloned for the same reason (and 30 years have passed since the cloning of the first mammal).
“But, furthermore, this artificial egg may have other uses in biotechnology and biomedicine. For example, transgenic hens are being used to produce proteins with therapeutic functions in egg whites. With this system, if it can be scaled up, production would be more efficient.
“Naturally, ethical questions remain regarding Colossal’s ultimate objectives, and it is legitimate to ask whether it makes ecological sense to genetically redesign some modern birds to superficially resemble moas, and what fate would await such animals. Would we release them on New Zealand’s South Island? As with other examples publicised by the same company — one need only recall the mammoth or the giant wolf — there is a rather surprising mix of scientific advances and publicity that could be described as misleading, which transcends the scientific sphere and must always be interpreted in the context of a private company’s business interests.”
Lluís Montoliu, research professor at the National Biotechnology Centre (CNB-CSIC) and at the CIBERER-ISCIII, said:
“Colossal Biosciences, a company with a name as spectacular as its ambitions, has just announced a new development – once again via a press release from the company itself, rather than through the usual channel of publishing its findings in a scientific paper. Colossal rose to fame in 2021 with the surprising initial proposal by George Church, the company’s promoter and founder, to de-extinct the woolly mammoth, a pachyderm that went extinct 4,000 years ago, the last of which survived on an island in northern Siberia. Among the many challenges such a de-extinction project would face was that of gestating an embryo, a mammoth foetus. It was impossible to use the species most closely related in evolutionary terms, the Asian elephant, with which they share a common ancestor that lived some 6 million years ago—too distant. It would not work. That is why they have opted for extrauterine gestation, using an artificial womb—a pouch that allows the developing foetus to be nourished and oxygenated—whose initial successes have already been reported in the gestation of lambs, in research aimed at saving premature babies at increasingly earlier gestational ages. Logically, to gestate a mammoth calf, this extrauterine sac will have to be scaled up to the necessary size. This development is not yet available, but Colossal is currently busy incorporating the more than 500,000 genetic variants of the mammoth genome into the genome of Asian elephant cells using CRISPR gene-editing tools. They will likely not need the artificial womb for some time yet.
“When it comes to de-extincting birds, the challenge is different. Birds develop externally, inside eggs, and some of the birds they wish to bring back to life, such as the giant moa of the South Island, currently have no similar or compatible species capable of producing eggs of the necessary size (80 times the volume of a hen’s egg, with a length of up to 24 centimetres). The giant moa was a flightless bird that inhabited the South Island of New Zealand; it stood almost 4 metres tall and weighed over 230 kilograms. It became extinct in the mid-15th century, following the arrival of the Maori from Polynesia, who hunted it to extinction. Colossal has set out to de-extinct the giant moa and, to this end, has now announced in a press release the biotechnological breakthrough achieved by its researchers. They have developed an incubation platform – an artificial egg of scalable size – protected by a transparent membrane that allows the embryo’s development to be observed and facilitates the necessary gas exchange and adequate oxygenation of the developing embryo. The tests have been successfully carried out using chicken embryos, which have completed their development until hatching, leaving this artificial egg and being born normally.
“Colossal is proving itself to be a unique biotechnology company, tackling challenges that would seem impossible for any other firm. However, at Colossal, they are tackling challenges that require the development of technologies and devices that do not yet exist, such as the artificial womb to gestate a potential woolly mammoth foetus or, now, the artificial egg for the development of bird embryos capable of hatching from species that, like the giant moa, ceased to exist over five centuries ago, or the dodo, also driven to extinction by humans in the 17th century. They have already demonstrated their skill by incorporating multiple genetic edits using CRISPR, including seven modifications discovered in the mammoth genome to create fascinating woolly mice, or up to 14 edited genes to modify the nucleus of a grey wolf cell and produce animals with characteristics similar to those that the giant North American white wolves must have had, which became extinct 13,500 years ago.”
Prof Dusko Ilic, Professor of Stem Cell Sciences, King’s College London (KCL), said:
“This is a technically interesting development, but it is important to distinguish the platform technology from the broader de-extinction narrative.
“Recreating an extinct species such as the moa would require far more than an incubation platform, including accurate genome reconstruction, appropriate development, physiology, behaviour, welfare and ecological context. Even then, the result would likely be an engineered proxy rather than a true restoration of the extinct species.
“The most credible translational value may therefore lie in applications such as embryo rescue, endangered bird conservation and controlled generation of genome-edited avian lines, particularly if it proves reproducible, scalable and compatible with normal long-term health, rather than in de-extinction itself.”
“At this stage, without access to the underlying data or a peer-reviewed scientific paper, it is difficult to properly assess the strength of the evidence, the methodology, or how reproducible and translatable the findings may be.”
Dr Louise Johnson, Associate Professor of Evolutionary Genetics, University of Reading, said:
“Artificial, transparent substitutes for eggshells have been used before to grow bird embryos, but they’ve never worked very well. Colossal appear to have developed a better one and made it easier to manufacture. It sounds impressive, but then it would, because it’s a press release. We’d need to see actual data to know how big a step forward this work represents. I look forward to reading more details when they’re published, but until there’s a peer-reviewed paper I might as well give expert commentary on a YouTube ad. “
Dr Megan Davey, Group Leader, The Roslin Institute, University of Edinburgh, said:
“There has been no published paper alongside this press release, which limits scientific scrutiny.
“The majority of species on Earth, including birds, monotreme mammals and many reptiles, develop their young in eggs outside the mother. Colossal’s development of an artificial egg shell for birds is a major step towards laboratory-based conservation biology, not only for birds but perhaps, in the future, for other egg-laying endangered species.
“Until now, the hypothetical but unproven approach has been to use a surrogate animal as a host to lay eggs containing the embryo of a different species, but this has had limited success for several reasons. This advance particularly addresses the challenge of scaling eggs to the appropriate size for each species: some birds, such as endangered songbirds, have very small eggs, while others, such as the kiwi and the extinct moa, have very large eggs. Natural egg shells are complex biological membranes that protect the growing embryo from physical damage and infections but also allow precise gas exchange to the growing embryo. The engineering of an artificial egg shell that can replicate these functions is an impressive act of bioengineering. Additionally, as the artificial eggs are transparent, this will allow monitoring of embryo health, while also supporting animal welfare and aiding successful hatching. The artificial egg is likely to be a technology which will have broader applications in the poultry industry.”
The press release from Colossal with the title ‘Colossal Biosciences Hatches First Chicks from Its Fully Artificial Egg System’ is under embargo until 13:00 UK time on Tuesday the 19th of May 2026.
Declared interests
Prof Dusko Ilic: “I declare no interest.”
Dr Louise Johnson: “I don’t have any conflicts of interest”
Dr Megan Davey: “none”
For all other experts, no reply to our request for DOIs was received.