Colossal’s artificial eggshell faces oxygen proof gap

Colossal’s artificial – Colossal Biosciences says it has built an artificial eggshell with a silicone membrane designed to let oxygen pass like a chicken eggshell—an approach it claims could support very large eggs. But without experimental efficiency data, experts question whether i

On paper, it’s the kind of breakthrough that makes a long-dead bird feel suddenly possible. Colossal Biosciences says it has developed an artificial eggshell built from a lattice supporting a transparent silicone membrane. and that this design could let it create eggs as large as the moa’s. The moa—New Zealand’s enormous. flightless bird—stood over 3 metres tall. weighed over 200 kilograms. and laid eggs larger than those of any living bird.

The scale matters because the moa’s egg problem is not decorative. It’s biological. Colossal is trying to solve the hurdle that prevents so-called “ex-ovo” approaches from succeeding: how to replace the eggshell’s job of regulating oxygen for a developing embryo.

Colossal’s claim sits in a grey zone that sounds bold but has familiar echoes. The company uses the term “artificial egg” in its press release. but what it has actually described is an artificial eggshell. Either way, it isn’t a first. Chicken eggs can be removed from their shells and hatched in materials as mundane as plastic cups to cling film. but survival rates tend to be low because. without an eggshell. embryos may not get enough oxygen. That’s why teams around the world have been working on more sophisticated ex-ovo approaches.

Colossal’s answer is its silicone membrane. The company says the membrane allows oxygen through at the same rate as a chicken eggshell and that it doesn’t require additional oxygen. It also says this could enable eggs as large as the moa’s.

But the missing piece is what experts want most: numbers.

Ben Novak. of the non-profit wildlife conservation group Revive & Restore. says he would “love to see what the numbers are on efficiency”—specifically. how many chicks hatch versus how many don’t. Without experimental results backing Colossal’s assertions. the promise hangs on an untested assumption: that oxygen delivery really will match a natural chicken eggshell.

Even if the oxygen problem is solved for chicken-sized eggs, larger eggs bring their own physics and chemistry. Larger eggs might need shells with different properties because of their lower surface-area-to-volume ratio. That could, in principle, be handled by tweaking the permeability of the membrane. The bigger question is what a moa egg actually contains.

Moa eggs were up to 24 centimetres long and 18 cm wide. That size means far more egg white and yolk than the eggs of living birds. Adding more egg white is described as relatively straightforward. Chickens have been successfully hatched in the egg white from turkeys. suggesting the source of the egg white may not be a major obstacle.

The yolk is the complication that doesn’t scale as easily. Each egg yolk is a single cell. Novak points out that ostrich yolks are the largest single cells found on the planet. and that making a yolk larger would require penetrating the cell membrane and injecting more yolk—something that would likely burst the cell. The workaround would likely be to enlarge the cell membrane so it can hold the extra yolk. which Novak says is probably doable given enough time. effort and money.

And even if every one of those technical problems were solved, the moa still wouldn’t simply come back. The barrier isn’t incubating a large egg; it’s genetics over time. DNA breaks down into smaller and smaller pieces, and all nine species of moa went extinct around 600 years ago. With that reality. it’s “never going to be possible” to get a complete. working copy of a moa genome and produce a living animal genetically identical to any of the extinct species. Even the human genome wasn’t completed until 2023.

Colossal’s wider claims have already collided with that skepticism. The company has been associated with de-extinction talk, including an assertion that it brought back the dire wolf. In reality, it made a few gene edits to grey wolves and called them dire wolves. Colossal’s head scientist conceded as much in an interview with New Scientist last year. even as the company itself still claims the gene-edited grey wolves are dire wolves. Independent researchers also dispute the “dire wolf” framing.

Vincent Lynch, at the University at Buffalo in New York, told New Scientist recently that in the circles he’s in there is “unanimous agreement that these claims are unjustified.”

So when Colossal’s artificial eggshell is presented as part of a moa comeback. the technical wonder does not automatically translate into ecological resurrection. In the sense of creating living animals genetically identical to extinct ones, de-extinction remains impossible. What could be done instead is creating a hybrid—an engineered animal resembling an extinct one while mixing living-species DNA with selected edits.

Revive & Restore, for example, aims to modify the band-tailed pigeon to create a bird resembling the extinct passenger pigeon. Novak is clear that this would be a hybrid and not a passenger pigeon.

Is this what Colossal aims to do with the moa?. The company hasn’t revealed its plans. But based on what it did with grey wolves and “woolly mice. ” its aim will likely be to tweak a few genes in the emu to create something that looks a bit like the moa—even if that means making genetic changes not present in the moa genome. There’s an example inside Colossal’s wolf work: five of the 20 gene edits made to the grey wolves were changes not found in the dire wolf genome.

Nic Rawlence. at the University of Otago in New Zealand. says he doesn’t think Colossal is close to achieving even this for the moa. Rawlence argues that developing a genetically engineered emu and calling it a moa for no good conservation or ecological reason—describing it instead as an ecotourism venture—is still “a long way off.”.

And beyond scientific feasibility sits the question of consent and heritage. Rawlence says there is “widespread Māori and public opposition in Aotearoa New Zealand.”

That opposition doesn’t erase the technical value of the eggshell claim, but it reframes what the breakthrough can realistically do. Rawlence describes the artificial shell as “impressive and groundbreaking work all on its own,” even if it doesn’t solve the biggest obstacles to de-extinction.

If Colossal is right about oxygen transfer and embryo survival. the transparent artificial shell could still matter for conservation and research. Rawlence points to potential conservation uses such as captive breeding of critically endangered species. Novak also suspects Colossal itself may be interested in the research potential: the transparency of the shell would allow researchers to tweak genes related to physical development and watch how they affect developing chicks over time.

There may also be applications in research and poultry farming. The transparent design suggests a way to observe development directly while adjusting genetic variables—something conventional opaque shells don’t offer.

For now. the story is less about a moa returning to New Zealand landscapes and more about the hard. unromantic work of proving that a membrane can truly replace an eggshell’s oxygen function. Colossal says it can match oxygen delivery rates of a chicken eggshell and doesn’t require additional oxygen. Novak says he wants to see efficiency numbers—how many chicks hatch and how many don’t.

That gap between claim and data is where the excitement has to wait. The eggshell, if it performs as promised, may become a tool with wide scientific reach. But the moa—giant, extinct, and genetically unreachable in full—is still not something an eggshell alone can incubate into reality.

Colossal Biosciences artificial eggshell ex-ovo moa New Zealand extinct birds silicone membrane oxygen efficiency Revive & Restore de-extinction emu gene edits conservation breeding