Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
What is an old, retired scientist to do but look back on his career and find satisfaction in the good ideas he once had? (I just finished a great novel in which a superannuated Cuban musician does the same thing.) In line with that, reader Nick called my attention to a two-year-old video by Zach Hancock lauding a paper I wrote with my student, Allen Orr, as “one of the ten most influential papers in evolution.”
First, though, in April I bragged about another video by Zach Hancock (a professor at Augusta University) that put my book Speciation (also co-written with Allen Orr), as one of the ten most influential books in evolutionary biology (we were #10). I have to admit that I consider this book my most significant accomplishment in science, as it distilled the field of speciation down to a research program that succeeded in influencing research in the origin of species. It took us six years (each) to write.
I rarely look at Speciation now, though, for when I do I realize that when we wrote it I was at the top of my neuronal game, able to read, write, and synthesize far better than I do now. And when I open it and sample a page or so from the chapters I wrote, I think to myself, “Who is that guy? He was really savvy?!” I could not write it now, nor will either of us revise it.
But Zack had another video that I missed, one on the ten most influential papers in evolutionary biology. And again Allen and I made the list, coming it at #9 with the paper below we published in 1989 in Evolution. Note the dedication to Bruce Grant, under whom both of us studied at William and Mary (click title to read the paper):
I’ll add that this paper was at first rejected by Evolution on one reviewer’s claim that we could not use the method of correlation that we did, but the reviewer simply didn’t understand that method (it’s not rocket science). We argued with the editor, something I’d never done, and the paper was accepted.
Zack chooses papers in the field that have been cited more than a thousand times. and I’ll let him explain the findings in his video below (the discussion of our paper goes from 5:23 to 7:51).
A few corrections. To determine the relative divergence time between pairs of species or taxa, we used published data using genetic distance determined by gel electrophoresis; we did not “sequence genes”. The purpose of the paper, as Zack says, is to determine how reproductive barriers between species arise with time by looking at the degree of reproductive isolation (measured only as hybrid sterility/inviability or as mate discrimination) between groups and correlating that with electrophoretic genetic distance, which is a measure of divergence time.
Also, Zack emphasizes the “reinforcement” aspect of the paper (I’ve put that conclusion in bold below), but that is only one of its findings—granted, a nice one. But the overall conclusions are several-fold, as the paper’s abstract notes below, including the relative rates of evolution of postzygotic isolation versus one form of prezygotic isolation (mate discrimination) as well as showing early evolution of male versus female postzygotic isolation, which explains the phenomenon of “Haldane’s Rule“, a generalization first noticed by J. B. S. Haldane in 1922, but neglected until I took it up in 1985. This rule, pointing out the greater preponderance of sterility and inviability in heterogametic (XY or ZW) hybrids than in homogametic hybrids (XX and ZZ) is still subject to investigation and controversy, but has been a central focus of the genetics of speciation since 1985.
Here’s the abstract of our paper with the “reinforcement” finding shown in bold. Note the other findings, too:
To investigate the time course of speciation, we gathered literature data on 119 pairs of closely related Drosophila species with known genetic distances, mating discrimination, strength of hybrid sterility and inviability, and geographic ranges. Because genetic distance is correlated with divergence time, these data provide a cross-section of taxa at different stages of speciation.
Mating discrimination and the sterility or inviability of hybrids increase gradually with time. Hybrid sterility and inviability evolve at similar rates. Among allopatric species, mating discrimination and postzygotic isolation evolve at comparable rates, but among sympatric species strong mating discrimination appears well before severe sterility or inviability. This suggests that prezygotic reproductive isolation may be reinforced when allopatric taxa become sympatric.
Analysis of the evolution of postzygotic isolation shows that recently diverged taxa usually produce sterile or inviable male but not female hybrids. Moreover, there is a large temporal gap between the evolution of male-limited and female hybrid sterility or inviability. This gap, which is predicted by recent theories about the genetics of speciation, explains the overwhelming preponderance of hybridizations yielding male-limited hybrid sterility or inviability (Haldane’s rule).
Finally, Allen and I continued to collect data as new studies became available, eventually expanding the study to 171 taxon pairs—an increase of 41% in the amount of data. The results, published in Evolution in 1997, were similar to those of the earlier study, but stronger because they were based on more data. You can read the paper by clicking below.
Since electrophoretic analysis of species divergence is largely obsolete—everyone uses DNA sequencing now—the whole paper can’t be repeated with modern methods, but what has been done is analysis of a subset of species, and, as I recall (I’m not going to look up the papers), the results to date support those of our 1989 and 1997 papers.
A scientist is lucky if he or she has more than one or two good ideas in their career, and by that I mean an idea that influences their field in a substantial way. I’ve had about three, one of which is the analysis embodied in these two papers. And I have to pay tribute to Allen Orr (now retired, too): fiercely intelligent and hard-working—more a colleague than my graduate student. Both of us are honored to be included in the lists of ten books and ten papers discussed by Hancock. Josh and Esther Lederberg, W. D. Hamilton. Ronald Fisher, Sewall Wright—that is damn fine company!
I came across the following post by Professor David Hillis of the University of Texas at Austin, an evolutionist I much admire for his perspicacity and malleability: his ability to contribute to several different fields, including herpetology. (He also breeds longhorn cattle on his Double Helix Ranch in the Hill Country.) Of course one reason I respect his work is because many of his conclusions agree with mine!
One of them is his adherence to the Biological Species Concept formulated by Ernst Mayr, which basically states that two populations belong to the same species if, when they contact each other in nature, they can produce fertile hybrids. If they can’t for any reason, then they are members of different species. Nearly all evolutionists adhere to some form of the BSC, but I won’t go into the concept in depth as it, its problems and problems with alternative species concepts are covered in detail in my book Speciation written with Allen Orr.
One long-standing question in evolutionary anthropology is whether Neanderthals were a different species from “modern” Homo sapiens. Some anthropologists say they were different species, the former called H. neanderthalensis and the latter H. sapiens. But there is ample genetic evidence for interbreeding of the two forms in Eurasia, and for fertility of the hybrids, for many people outside of Africa carry Neanderthal genes. I myself have a small fraction of Neanderthal genes in my DNA. This kind of data is prima facie evidence that when the two groups were in contact, that they produced hybrids and also that those hybrids were fertile, backcrossing to modern H. sapiens.
At best, then, I consider the two forms to be subspecies: somewhat differentiated populations that were members of the same species. Those who agree with this, like me and Hillis, see the subspecies as H. sapiens sapiens and H. sapiens neanderthalensis.
The Neanderthals evolved from a hominin population that came to Eurasia out of Africa about 400,000 years ago. They persisted until about 40,000 years ago, when they (identifiable by fossil features; see below) mysteriously disappeared.
There have been several hypotheses accounting for the disappearance of the Neanderthals. They include demographic fluctuations or inbreeding leading to disappearance of the species, extinction due to inability to survive changes in the environment (there was glaciation when Neanderthals lived), competition (including aggression) from “modern” H. sapiens who left Africa to populate the world about 60,000 years ago, and “extinction through interbreeding”, which is the hypothesis supported by a new paper discussed below in Nature Scientific Reports. I should add that “modern” H. sapiens arose in Africa about 300,000 years ago.
Click both screenshots to go to the comment and the paper.
This paper, by Swiss and Italian authors, shows that “extinction via interbreeding” is at least possible under reasonable and conservative conditions obtaining at the known times of extinction. Successive waves of H. sapiens coming out of Africa, they posit, interbred with Neanderthals and eventually, because the sapiens were far more numerous than Neanderthals, the Neanderthal genome became absorbed into the modern population of H. sapiens. Click to read; it’s highly mathematical and you should read just the abstract, introduction, and conclusions:
Here are a few of the assumptions:
Neanderthals consisted of tribes of about 500-1000 individuals, subdivided into “bands” of 25-50 individuals.
The total population of Neanderthals was about 5000-7000 individuals
The population of H. sapiens was ten to a hundred times larger than this
Repeated waves of H. sapiens came out of Africa, comprising an effectively infinite reservoir of individuals and genes
The genetic data in modern H. sapiens shows repeated instances of introgression
The upshot: The “genetic dilution” or “extinction through interbreeding” hypothesis can be supported by a reasonable mathematical model that takes into account evidence of population sizes and times of migration, and accounts for the genetic data. This does not mean, of course, that this is why the Neanderthals disappeared. It could have been another scenario or perhaps a combination of this scenario with others. Mathematical models can only tell us what is possible, not what is true. But the paper does show that an interbreeding scenario cannot be ruled out.
And the genetic data we do have, including ancient DNA data from Neanderthal bones, shows that we and Neanderthals are brothers and sisters: members of the same species. There were other distinct biological species that arose during hominin evolution, but Neanderthals and modern humans were almost surely “conspecific.”
The paper’s conclusions:
The mathematical model we presented provides a plausible explanation for the gradual disappearance of Neanderthals, suggesting that their genetic assimilation with H. sapiens, a demographically much larger species, may have been a significant factor in their decline. Rather than sudden extinction, our model proposes that repeated cycles of H. sapiens immigration leading to the Neanderthal gene dilution, could account for the Neanderthals’ disappearance and the observed patterns of Neanderthal ancestry in modern human populations. Although this model provides a possible robust genetic explanation, it is important to note that it does not exclude other possible contributing factors that were not considered in our approach, such as environmental changes, competition, or demographic fluctuations. Evidence of interbreeding and genetic introgression supports the notion that H. sapiens and Neanderthals interacted extensively over thousands of years. Therefore, the interplay of genetic, demographic, and environmental factors likely contributed to the complex process of Neanderthal demise.
Future studies incorporating both genetic and archaeological data will be crucial in refining our understanding of this pivotal moment in human evolution.
Here’s a Neanderthal skull showing distinctive subspecific features (from Wikipedia):
Carl Zimmer and Catrin Einhorn are the authors of a new article in the NYT about our old friend Colossal Biosciences, which you’ll remember as the outfit in Texas that has promised to “de-extinct” the woolly mammoth, the thylacine (marsupial “wolf”), the dodo and the moa, after having claimed that they’ve already de-extincted the “dire wolf”.
As I’ve written at length here (and in an article in the Boston Globe), Colossal has not de-extincted anything. It simply edited 14 genes in a gray wolf cell, and then put that cell into the nucleus of a domestic dog egg. What came out were three slightly tweaked gray wolves, white in color and, Colossal says, larger than normal wolves. But 14 changed genes in a genome of about 20,000 protein-coding genes, and having 2.5 billion DNA bases, does not turn a gray wolf into a dire wolf. Their response was that a dire wolf is anything that you think resembles a dire wolf, no matter how much. That is disingenuous.
I lost respect from Colossal when they decided to double down on their claim that they’ve brought something back from extinction, which they surely have not. And their claims that they will release these things into the wild—their ultimate aim—is ridiculous. The three faux white dire wolves (I doubt the original was even white) are kept secretly on an enclosure somewhere in the West, with only a few toadying journalists or donors allowed to visit them.
Likewise, Colossal’s promise to give us woolly mammoths by 2028 is unbelievable, for they won’t be able to put an engineered Asian elephant egg into the endangered Asian elephant, much less produce a creature that has more than a minute fraction of mammoth DNA. On top of that, Colossal says their aim is to release these faux mammoths on the tundra, which won’t happen, and that when they do so, it will help with global warming since the furry elephants’ trampling on the permafrost will prevent release of carbon dioxide into the atmosphere, ameliorating global warming. Gullible donors like Paris Hilton, Tiger Woods, and Tom Brady have swelled Colossal’s coffers by $400 million, and it’s now worth, notes the article below, more than $10 billion.
I think that when Colossal realized it couldn’t make good on its de-extinction promises, it started investing in other projects. One of them is described in this article in the NYT (click below or find it archived here). What they propose to do, with the promised help of the Trump administration, is save the DNA from endangered species. Now this project has its good aspects, for if Colossal sequences a lot of new genomes and publishes the sequences (which it promises to make public), we could learn quite a bit about evolution. And the American taxpayer doesn’t have to foot the bill for any of it. But Colossal has no experience in “biodiversity banking” of this sort, even though nonprofit conservation organizations like the San Diego Zoo Wildlife Alliance has been doing it for over half a century (Colossal is decidely a for-profit company). The San Diego noprofit has in fact created clones of black-footed ferrets, a highly endangered species, from biobanked material, so at least it has something useful to show for its efforts.
Further, if Colossal is doing this for “de-extinction” purposes, and will retain sole possession of the material, as it will do, then it is preventing other organizations or scientists from using what is “banked.” The U.S. government has no business partnering with such an enterprise. I don’t worry about de-extinction because that is (pardon the pun) a dead issue. But the concentration on biobanking may, as the authors note, “erode support for on-the-ground conservation,” which mainly involves saving existing habitat and keeping humans from destroying new habitat.
A few quotes from the article, which, as science journalism should, maintains a neutral viewpoint while emphasizing both pros and cons:
The Trump administration and a company that is promising to bring long-gone animals back from extinction announced a partnership on Thursday to preserve cells, tissue and DNA from threatened and endangered species.
The company, Colossal Biosciences, said its goal was to store samples from every animal and plant protected under the Endangered Species Act, which includes more than 2,300 listings worldwide.
As more species face the risk of extinction, scientists see such biobanks as a critical backup. But concerns are also growing that the rise of genetic engineering and efforts to revive extinct species will erode support for on-the-ground conservation, which often requires protecting habitat from drilling, mining and other development.
The announcement comes as the Trump administration has been rolling back protections on land and water, including through actions to weaken the Endangered Species Act, in favor of expanded oil and gas exploration, commercial fishing and other economic activities.
“This partnership brings together the scientific expertise of the U.S. Fish and Wildlife Service and the ingenuity of the private sector to develop new tools that can help recover species, preserve critical genetic resources, and strengthen the future of wildlife conservation,” Doug Burgum, the interior secretary, said in a statement.
Under a memorandum of understanding, Colossal and the Fish and Wildlife Service will collaborate to identify high-priority actions, and the government will provide a list of which species it wants to prioritize.
Well, I’d prefer that a consortium of scientists decide which species should be prioritized, and I’d prefer that the material be given to the San Diego Zoo organization rather than to Colossal, which will have sole use of the material and is a for-profit organization. The agreement is supposed to run for five years, and that Colossal gets to keep all the samples it collected with its own funding, equipment, or personnel”, which means pretty much all the samples.
Colossal has been busy doing other stuff, too:
After beginning its de-extinction efforts, Colossal branched out into biobanking. In February, the company announced a partnership with the United Arab Emirates to build what it calls a BioVault in Dubai, intended to store cell and tissue samples from more than 10,000 species.
Why Dubai? Why not store all the material in one place? Who knows? And they clone pets!
[Colossal] currently gets revenue from cloning pets and horses through a company it acquired last year, and claims to have future sources of revenue from licensing technology it develops for its de-extinction projects.
The article notes some criticism of Colossal’s proposal, too (I’m not quoting the criticism of the “de-extinction” endeavors, which the article also mentions):
But some conservation biologists expressed worries about depending so much for the long-term guardianship of precious samples on a private company.
“It seems like a bit of a risk for the U.S. government to place biomaterials in a for-profit company that doesn’t have a very long track record,” said Oliver Ryder, a conservation geneticist at the San Diego Zoo Wildlife Alliance, which operates a storage effort called the Frozen Zoo that has been preserving cells for about 50 years.
and
Gabriela Mastromonaco, chief science officer at the Toronto Zoo, called the U.S. plan laid out in Thursday’s announcement hugely ambitious.
“To collect every threatened and endangered species, that is a massive endeavor,” she said. “That means tracking, trapping, immobilizing, and getting your hands on a lot of animals.”
She expressed concern that the initial announcement was short on planning details that would be standard in many other nations.
. . . Dr. Mastromonaco of the Toronto Zoo said the announcement left many questions unanswered, such as how Indigenous communities would participate in decisions about the program and the rules for who gets to use the samples for research. She said she was addressing these questions herself as Canada develops its own plan for biobanking wild species.
and
Concerns that genetic engineering would replace critical conservation work heightened when Mr. Burgum, the interior secretary, celebrated the company’s announcement on X, writing that “the marvel of ‘de-extinction’ technology can help forge a future where populations are never at risk.” The Fish and Wildlife Service is part of the Interior Department.
Colossal executives emphasize that their efforts are intended to add to conservation strategies, not supplant the important work of protecting habitat.
I guess Colossal needs government cooperation since that’s required to collect DNA samples from endangered species. But if Colossal is dong this “for public good and impact” as Colossal CEO Ben Lamm has said, why do they retain the sole right to use the material? Even if it’s collected by Colossal, the permission to do so has to come from the U.S. government, and we should not be entangled with a private, for-profit company that will store material only it can use.
I see Colossal as having provided some valuable knowledge, but also largely as a pack of grifters, making promises they cannot keep and distorting what they have done. In my view they should stick to cloning Fido and Fluffy for rich pet-owners who want to “de-extinct” their postmortem pets.
Leucism, the absence of pigment in all or parts of the body in animals, is a genetic condition often mistaken for albinism (leucistic animals havenormally pigmented eyes). It’s found in all sorts of animals, from reptiles to mammals, and Scott Ritchie has spotted it in Australian ducks. Scott sent some pictures, which you can enlarge by clicking on them, and his captions are indented:
The leucistic Plumed Whistling Duck (Dendrocygna eytoni), is back at Hasties Swamp, Queensland, the white one in in middle. We have seen it for at least 2 years running. And “he/she” appears to have busy, with at least one (several white light feathers head and breast), and perhaps 3 (2 based on “forehead” feathers) individuals showing leucicism traits. It’s interesting that they were hanging together at the log to the left of the hide.
After announcing that it would “de-extinct’ the Woolly Mammoth, and that it had in fact “de-extincted” the Dire Wolf, the company Colossal Biosciences is now making big noises about its effort to bring back extinct big birds: the giant moas of New Zealand (driven extinct by humans around 1300 AD) and the dodo of Mauritius (also killed off by humans in 1662). These are big birds (dodos weighed from 20-40 pounds, moas, of which there were nine species, from 55 to 600 pounds), and this fact alone makes it hard to de-extinct them.
But, as with the “woolly mammoth”, the concept of bringing back extinct species is impossible given our current technology, and saying that you can is grossly misleading. And that’s for several reasons (the indented bits below are mine):
1.) You need the DNA of the extinct species if you’re going to create a simulacrum of it by injecting bits of the extinct animal’s DNA into the genome of a modern relative.
2.) You need to know what the DNA segments you have actually do in the animal, and how sequences differing between it and the donor genome can produce an animal with some traits of the original species. Where are the “big genes” in a mammoth, for example?
3.) Species are not “de-extincted”: what happens is that a living relative is genetically engineered by putting in a few bits of ancient DNA to create a “partial hybrid” that superficially resembles the ancient species. This involves finding and inserting a few bits of ancient DNA that you think will make the donor species look more like the extinct one. For example, I think fewer than 20 genes were engineered into a gray wolf genome to make the “dire wolf”. These included both dire wolf genes and mutant genes of modern dogs inserted into a gray wolf genome. The tweaked embryo was then implanted in a domestic dog. It’s important that you (and the press) realize that the ancient species is not brought back; what we get is a modern species that looks a bit like the ancient species. (See my post on the “dire-ish wolf” here.)
4.) There are problems with rearing the “tweaked” (I won’t call it “de-extincted”) species. We cannot artificially inseminate elephants with elephant genomes that have been engineered for hairiness and bigger tusk. We don’t have the ability to do this (though we might in the future), the embryos might not develop properly, and the mother is unlikely to take care of them. This is why Colossal has spoken of using “artificial uteruses” to rear the tweaked “mammothy” elephant.
5.) For giant birds like the dodo and moa, you need to be able to rear the tweaked species—presumably adjusted to be larger than its surrogate relative—in big eggs. Because those eggs don’t exist, they have to be made somehow. This week Colossal announced the creation of 3-D printed eggshells that could be used to contain a chicken embryo that develops to term. But of course hatching is one thing, and rearing is another. What mother will rear a tweaked “dodolike” bird. The closest relative of the dodo is the Nicobar pigeon, a bird considerably smaller than the dodo (the pigeon weighs about a pound). The closest living relative of the moas is the tinamou, which weighs about as much as a big chicken: five pounds max. Rearing such birds to maturity is a serious problem, even if they were full dodos or moas rather than tweaked pigeons or tinamous.
6.) Colossal has announced that a crucial part of “de-extinction” is “rewilding”: releasing the tweaked animals back into nature to restore their niche. This is one of the most questionable parts of the whole enterprise. The tweaked hairy elephant, for example, should be released on the tundra (and in groups of individuals, which is yet another problem, as you need to engineer more than one hybrid). That tundra doesn’t exist in the form it did in the past, and, of course, the tweaked hairy elephant has to have all genes necessary to seek out and use the food that a real woolly mammoth would eat, as well as genes for preferring as a mate others of its kind. It has to be able to survive extreme cold. We don’t know what genes these are! All we have are DNA sequences.
An example of the problems is Colossal’s announcement that it had “de-extincted” the Dire Wolf. It hadn’t: it engineered a gray wolf with about 20 inserted genes taken from both wolves and domestic dogs, producing a whitish wolf that seems a bit larger than gray wolves. Three of these creatures were made. Not only were they not released in the wild, but they are sequestered in a secret and tightly-controlled fenced area that is off limits to all but selected journalists.
All the brouhaha, then, is misleading. We don’t get extinct species back, we may not even get “tweaked” species back, and they are very unlikely to ever see the wild again. I discussed many of these problem in an op-ed last year in The Boston Globe (archived here). See also the New Scientist article below.
Because Colossal has misled the public—they originally said they’d de-extincted the dire wolf, then retracted that claim, then reinstated it, saying that if it looks like a dire wolf, it is a dire wolf—each time they accomplish something they tout it as a huge advance towards real de-extinction. After all, they have to keep their rich investors and the public happy.
The latest Colossal announcement, which came through the mail, is that of their developing an artificial chicken eggshell. The problem is (see below the fold) that this has already been done by others some time ago. A further problem, of course, is that this is only a minor issue in the problem of putting dodo-like or moa-like embryo in an artificial egg. Here’s Colossal’s announcement, and note the emphasis on “de-extinction”:
BREAKTHROUGH: De-Extinction Just Got Its Egg
Step inside the beginnings of life as Colossal Biosciences hatches live chicks from our new artificial egg.
This huge advancement is foundational to our de-extinction of the South Island giant moa, whose eggs were around 80x the volume of a chicken’s. No living bird could possibly hatch one. So we built an artificial egg that will.
Watch a real chick embryo develop inside the artificial egg. Get a full breakdown of every feature. And see how this breakthrough is opening new doors for avian biotech research and bird conservation.
You’ll want to see the ending.
Meet the Colossal artificial egg. Nature spent millions of years perfecting the original. We just made our own, and hatched some beautiful and healthy chicks.
Here’s how it works:
Egg-shaped frame: a lattice shell that gives the whole system its structure and protection.
Colossal membrane: the secret weapon. A bioengineered, gas-permeable layer that matches a real shell’s oxygen transfer, so O₂ flows in and CO₂ flows out exactly the way nature does it.
See-through build: the largely transparent design that lets us watch development in real time. This is critical for research and for de-extinction, where visually confirming milestones and the gene-edited traits we’ve put back is everything.
Modular scale: the platform will stretch to fit eggs of any size, including the South Island giant moa egg, roughly 80x the volume of a chicken egg.
Extinction doesn’t have to be the end. And this is just the beginning.
Avian de-extinction is getting wild.
Here’s a breathy, chest-thumping video, accompanied by triumphant music, making it seem that the problem of de-extinction is on the way to being licked:
This is an achievement, of course, but to me it’s not a substantial step towards getting back moas and dodos. as it’s not that new.
And of course the press has picked it up, but this time they are careful to quote Colossal’s many critics as well as its chief propagandist, Ben Lamm. The Times of London talks about the eggshell as a step in resurrecting moas, using emus as surrogate moms. Click headline below to read:
Excerpts from The Times piece:
Colossal Biosciences, a Texan biotechnology firm, has developed a shell-less system it says is capable of supporting a bird embryo from early development through to the point of hatching.
So far the device has been used to produce baby chickens. The end goal, the company says, is to deploy a much larger version to resurrect the moa, whose eggs were about 80 times the volume of a farmyard hen’s.
. . . . So far the device has been used to produce baby chickens. The end goal, the company says, is to deploy a much larger version to resurrect the moa, whose eggs were about 80 times the volume of a farmyard hen’s.
. . .Eventually, the hope is that emu cells can be edited, introducing genetic changes that would make any resulting animal more moa-like. The hurdle then would be where to grow an embryo. According to Colossal, the eggs of the South Island giant moa were roughly eight times the volume of an emu’s. No living bird would be large enough to play mother to it.
This is where the artificial egg would come in. Colossal says the device could be scaled up, allowing embryos of much larger birds to develop in a controlled chamber. It claims this could remove the need for a living surrogate mother and make it possible to incubate embryos at sizes no modern bird can manage.
But they quote critics!
. . .Critics say such claims need careful handling. To recreate a mammoth, for instance, Colossal plans to alter the genetic code of an Asian elephant.
Even if that succeeds, sceptics argue the result would not truly be a mammoth, but an elephant engineered to have some mammoth-like traits, such as shaggy hair and extra fat reserves.
The same issues apply to the moa. The project, which is being backed by Sir Peter Jackson, the film director behind the Lord of the Rings trilogy, plans to compare ancient DNA from the extinct species with living relatives such as emus and tinamous to work out which genetic features helped make a moa a moa.
Well, there’s the rub! But Ben Lamm is always around to give the necessary donation-promoting optimism:
Ben Lamm, chief executive of Colossal, said: “Restoring species like the South Island giant moa isn’t just about reconstructing ancient genomes and editing [primordial germ cells, which eventually become sperm or eggs] — it requires building an entirely new incubation system where no surrogate exists.”
He added: “It’s a major milestone for Colossal and a foundational technology for our de-extinction toolkit.”
Again, I’m not saying that the artificial egg is not of any value. I’m just saying that insuperable problems remain with bringing back moas (or dodos).
Here’s a tweet that Matthew sent me, which called my attention to a New Scientist article that, mirabile dictu, strongly criticizes the de-extinction program as a whole:
Colossal says its "artificial egg" will help it bring back the moa, which had larger eggs than any living birds 🧪But it's really just an artificial eggshell, and even clingfilm will work – sort of – as an artificial eggshell. Plus there's the yolk problem…www.newscientist.com/article/2527…
The article at New Scientist can be found by clicking on the screenshot below, or finding it archived here:
A few Q&As from the piece:
Is this the first-ever artificial bird egg?
Colossal does use the term “artificial egg” in its press release, but it is really just an artificial eggshell. Either way, it isn’t a first – in fact, it’s possible to remove chicken eggs from their shells and hatch them from anything from plastic cups to cling film. However, the survival rate is usually low because, without an eggshell, the developing chicks may not get enough oxygen. A number of teams around the world have been working on more sophisticated so-called ex-ovo approaches.
How much better is it than cling film?
Colossal claims its silicone membrane is better than existing ex-ovo methods because it allows oxygen through at the same rate as a chicken eggshell and doesn’t require additional oxygen. However, it hasn’t released any experimental results to back this up. “I would love to see what the numbers are on efficiency,” says Ben Novak of non-profit wildlife conservation group Revive & Restore. “How many of these chicks hatch versus how many don’t?”
Colossal doesn’t publish much of the data that would enable scientists to see exactly what it did, which genes it used, and what the results are. Three more issues:
Does this mean we could create a giant artificial moa egg?
Even if Colossal’s approach does work well for chicken eggs, it won’t necessarily work for larger eggs. Larger eggs might need shells with different properties because of their lower surface-area-to-volume ratio, but this could probably be solved by tweaking the permeability of the membrane. Making a big egg also requires more than just a big eggshell. Moa eggs were up to 24 centimetres long and 18 cm wide, so they contained a lot more egg white and yolk than the eggs of living birds. Adding more egg white should be relatively straightforward. Chickens have been successfully hatched in the egg white from turkeys, says Novak, which suggests it won’t matter much what animal’s egg white is used.
How much better is it than cling film?
Colossal claims its silicone membrane is better than existing ex-ovo methods because it allows oxygen through at the same rate as a chicken eggshell and doesn’t require additional oxygen. However, it hasn’t released any experimental results to back this up. “I would love to see what the numbers are on efficiency,” says Ben Novak of non-profit wildlife conservation group Revive & Restore. “How many of these chicks hatch versus how many don’t?”
What about the extra yolk required?
That’s more of a problem. Each egg yolk is a single cell, meaning ostrich yolks are the largest single cells found on the planet. To make a yolk larger would require penetrating the cell membrane and injecting more yolk, says Novak, which would likely cause the cell to burst. So it might be necessary to somehow enlarge the cell membrane so it can hold the extra yolk. Which is probably doable, given enough time, effort and money.
And the $64,000 question (and answer):
If all the problems with making really big eggs are solved, could we then bring back the moa?
Absolutely not. The big problem is that DNA breaks up into smaller and smaller pieces over time, and all nine species of moa went extinct around 600 years ago. 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.
. . . . Is this what Colossal aims to do with the moa? [i.e., tweaking existing species with a few gene edits]
Colossal 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 a bit like the moa in appearance, even if that means making genetic changes not present in the moa genome. Five of the 20 gene edits made to the grey wolves were changes not found in the dire wolf genome, for instance. Nic Rawlence at the University of Otago in New Zealand doesn’t think Colossal is close to achieving even this for the moa. “The development of a genetically engineered emu and calling it a moa for no good conservation or ecological reason, but rather an ecotourism venture, is still a long way off,” says Rawlence. Nor is the idea of bringing back the moa universally welcomed, he says. “There is widespread Māori and public opposition in Aotearoa New Zealand.”
Grok agrees with all this when I asked it the question below:
From Grok:
Question I asked it: Will Colossal be able to bring the moa and the dodo, that is, “de-extinct” them?
Grok’s answer:
No, not in the sense of resurrecting the exact extinct species—but Colossal Biosciences could plausibly create moa-like and dodo-like engineered proxy birds (genetically modified versions of living relatives) within the next 5–15 years, assuming continued progress. True de-extinction (reviving genetically identical copies of the original species) is not possible with current or foreseeable technology.
There’s more at New Scientist, but you can read it at the link or the archived link. I hope I’ve shown that Colossal is engaged in misleading the public (and I can’t help but think it knows this, since it de-emphasizes the “tweaking” part), and that you’ve learned some of the problems with its “de-extinction” claims.
Below the fold I’ve put Grok’s answer to my question about whether previous workers had reared chicken eggs using artificial “shells” previously. The answer is “yes,” though Colossal’s expensive shell is more sophisticated. I cannot vouch for the accuracy of Grok’s answers, but of course it tells you how to investigate them.
The Proceedings of the National Academy of Sciences finally published an obituary of J. D. Watson, who died in November of last year. (Nathanial Comfort has written a biography of Watson that will be a good complement to Matthew’s biography of Crick; Comfort’s book will be out at the end of this year or the beginning of 2027.) You can access the PNAS obituary for free by clicking on the screenshot below, which is a good summary of Watson’s accomplishments (and missteps) if you don’t want a book-length treatment.
Most laypeople, if they know Watson’s name, probably know just two things. First, he and Crick co-discovered the structure of DNA, one of the great findings of biology. Second, Watson was demonized, and fired as director of the Cold Spring Harbor Laboratories, for making racist comments. Both are true. Yes, Watson was a racist, as I discovered from talking to him for an hour and a half (see below), but he was also a brilliant scientist who did far more than just the DNA-structure stuff. The article describes some of his other accomplishments and I quote:
DNA was not the only structure that Watson solved at Cambridge. Using X-ray crystallography, Watson determined that the coat protein subunits of Tobacco Mosaic virus (TMV) were arranged helically around the viral RNA, although he could not detect the RNA (5). Two years later, Rosalind Franklin, now at Birkbeck College with J. D. Bernal, published the definitive study on the structure of TMV (6).
Watson left Cambridge in 1953 to take up a fellowship with Delbrück at the California Institute of Technology. He joined forces with Alex Rich in Pauling’s laboratory to work on the structure of RNA, but RNA gave fuzzy X-ray diffraction patterns and provided no clues as to what an RNA molecule might look like. Watson was not happy in Pasadena and, with the help of Paul Doty, was appointed an assistant professor in the Department of Biology at Harvard. However, he first spent a year in Cambridge, United Kingdom, before moving to Cambridge, Massachusetts.
Watson and Crick teamed up again to study the structure of small viruses and proposed that as a general principle, the outer protein coat of these viruses was built up of identical subunits. Franklin was also studying small viruses, and she and Watson exchanged letters, and she asked Watson and Crick to review drafts of her manuscripts.
At Harvard, Watson, his colleagues, and students made many important findings on ribosomes and protein synthesis, including demonstrating, concurrently with the team of Sydney Brenner, Francois Jacob, and Matt Meselson, the existence of messenger RNA. Watson’s contributions are not reflected in many of the publications from his Harvard laboratory. He did not add his name to papers unless he had made substantial contributions to them, thus ensuring that the credit went to those who had done the work. These papers included the discovery of the bacterial transcription protein, sigma factor, by Watson’s then graduate student Richard Burgess, along with Harvard Junior Fellow Richard Losick. At Harvard, Watson also promoted the careers of women, notably providing support for Nancy Hopkins, Joan Steitz, and Susan Gerbi. He also contributed to the split in the Department of Zoology due to his contempt for those working in the Department who were antireductionists.
In his last scientific paper (7), published in 1972, Watson returned to DNA. In considering the replication of linear DNA of T7 phage, he pointed out that the very ends of a linear DNA molecule cannot be replicated, the “end replication problem” which is solved in eukaryotes by telomeres. (Watson’s work was predated by Alexey Olovnikov who had published the same observation in 1971 in a Russian journal.)
Note the contributions Watson made, along with collaborators, at Harvard, and note as well that he did not put his name on publications unless he made “substantial contributions to them.” I did that, too, and I inherited that practice from my Ph.D. advisor Dick Lewontin, who inherited it from his Ph.D. advisor Theodosius Dobzhansky, who inherited it from his research supervisor at Columbia and Cal Tech, the Nobel Laureate T. H. Morgan. This is a good practice, and I never suffered from keeping my name off papers, for the granting agencies care only about which and how many papers come from an investigator’s funded lab, not how many his or her name is on. I’ll digress here to say that this practice has almost died out, as people now slap their name on paper for paltry reasons, like they contributed organisms or other material. The reason is the fierce competition for funding and credit.
Watson went on to write influential textbooks, trade books (notably The Double Helix) and headed up the Human Genome Project, from which he ultimately resigned. Finally, he ran the Cold Spring Harbor Laboratory, which he did very well until the racism scandal broke, rendering him ineffective.
Witkowski and Stillman don’t neglect the dark side of Watson:
In the late 1990s, Watson gave seminars, notably at the University of California Berkeley, where he expanded on research on the hormone POMC and related peptides and made inappropriate and incorrect observations about women. In October 2007, he made racist remarks about the intelligence of people of African descent, and, damagingly for his fellow employees at CSHL, stated that while he hoped that everyone was equal, “people who have to deal with black employees find this not true.” The CSHL Board of Trustees dissociated the institute from Watson’s comments, and he was forced to step down from his administrative position as Chancellor. The matter resurfaced in January 2019 when Watson was asked if his views on race and intelligence had changed. His answer was unequivocal: “No, not at all.” The Laboratory’s response was immediate, relieving him of all his emeritus titles. Watson and his family, however, continued to live on the CSHL campus.
They conclude this way:
Jim’s remarkable contributions to science and society will long endure—for the scientists using the human genome sequence, for students using Molecular Biology of the Gene and for readers of The Double Helix, and for reviving Cold Spring Harbor Laboratory. He was a most amazing man.
Here’s a photo of Watson and me when he visited Chicago in 2013 to introduce the Watson Lectures that he endowed for our department. Do read the cool story about how those lectures came about in my post “Encounters with J. D. Watson“.
Here we have an 83-minute interview of Matthew Crick by Michael Shermer; the topic is Francis Crick as described in Matthew’s new book Crick: A Mind in Motion. Talking to a friend last night, I realized that the two best biographies of scientists I’ve read are Matthew’s book and Janet Browne’s magisterial two-volumebiography of Darwin (the two-book set is a must-read, and I recommend both, though Princeton will issue in June a one-volume condensation).
At any rate, if you want to get an 83-minute summary of Matthew’s book, or see if you want to read the book, as you should, have a listen to Matthew’s exposition at the link below. I have recommended his and Browne’s books because they’re not only comprehensive, but eminently readable, and you can get a sense of Matthew’s eloquence by his off-the-cuff discussion with Shermer.
Click below to listen.
I’ve put the cover below because Shermer mentions it at the outset of the discussion:
Egg-shaped frame: a lattice shell that gives the whole system its structure and protection.
Colossal membrane: the secret weapon. A bioengineered, gas-permeable layer that matches a real shell’s oxygen transfer, so O₂ flows in and CO₂ flows out exactly the way nature does it.
See-through build: the largely transparent design that lets us watch development in real time. This is critical for research and for de-extinction, where visually confirming milestones and the gene-edited traits we’ve put back is everything.
Modular scale: the platform will stretch to fit eggs of any size, including the South Island giant moa egg, roughly 80x the volume of a chicken egg.
