When scientists sequenced the Neanderthal genome in 2010, they found that Neanderthals interbred with human ancestors and then mysteriously went extinct. As a result, many people alive today share up to 4% of their DNA with Neanderthals.
This genetic advance has provided powerful new information about the evolutionary history of Neanderthals and Homo sapiens, but it has also raised new questions: Can Neanderthals be brought back?
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In 2025, Colossal Biosciences, a company co-founded by Church, made headlines by announcing plans to “annihilate” the dire wolf through cloning and gene editing, create genetically engineered “wooly rats,” and exterminate the dodo. Their ultimate goal is to exterminate the woolly mammoth.
But while Church was convinced a decade ago that a Neanderthal revival could happen in the near future, other experts told Live Science that a revival is currently an insurmountable challenge. Even if we could bring them back, they argue, there are many reasons why we shouldn’t.
“This is one of the most unethical things I could try. Please stop it completely,” Jennifer Ruff, a biological anthropologist at the University of Kansas, told Live Science about the idea of bringing them back.
Can Neanderthals be brought back to life?
Reviving Neanderthals is not technically easy. “You can’t just put the Neanderthal genome into a human egg,” Ruff said. “That won’t work.”
One of the problems with this process is the potential for immune system incompatibility. This often ruins cross-species pregnancies, as the host’s uterus rejects the fetus. (There is still debate as to whether modern humans and Neanderthals can be called separate species.)
Humans and Neanderthals successfully interbred in the past, and some human populations now have up to 4% Neanderthal DNA. “Other DNA may not have been informative, so it was slowly removed from the genome,” Ruff said.
Additionally, experts have found that the human Y chromosome lacks Neanderthal DNA, which may indicate a fundamental immune system incompatibility between Neanderthal male fetuses and the female Homo sapiens that carry them, even in the past. Other research suggests that genetic variations in the red blood cells of Neanderthal-human hybrid mothers may have led to high rates of miscarriage.
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Ruff said reintroducing Neanderthal genes, which have been removed by natural selection over thousands of years, into modern human eggs would likely have many unintended consequences.
Another method is cloning, but to clone one of its extinct cousins, “you need living Neanderthal cells,” Hank Greeley, director of Stanford University’s Center for Law and Life Sciences, told Live Science. Neanderthals went extinct over 30,000 years ago, so clearly we don’t have cells.
Using today’s CRISPR technology, a type of genome editing, it is possible to modify the genome of human cells to resemble that of Neanderthals. That’s what Colossal did when it modified a few genes in gray wolves to resemble dire wolves. But they weren’t actually scary wolves, just as Homo sapiens, which has a small number of Neanderthal genes, isn’t Neanderthal.
Additionally, CRISPR is not infallible, and it is difficult to incorporate many genetic changes at once.
“We may be able to make 20 to 50 changes now, but at some point we will be able to change everything,” Greeley said.
CRISPR technology can be used to cut and modify DNA sequences, but a new technique known as base editing, in which scientists change individual letters in the DNA code, could make precise editing of genomes easier and faster in the future.
“I think if we really wanted to, we could potentially have a baby born alive with a completely Neanderthal genome, probably within 20 years or so,” Greeley said. “But even if it were plausible, I don’t think we would do it for ethical and legal reasons.”
Is the extinction of Neanderthals ethical?
Exterminating Neanderthals is ethically repugnant, experts told Live Science. “The very idea of creating another kind of human being based on DNA using unconsensual and uncertain technology is morally repugnant,” Ruff said.
But human babies come into the world every day without consenting to be born, Greeley said. For him, ensuring the safety of the process and the results is the more important ethical issue at hand.
IVF patients can protect their children from certain genetic diseases by selecting embryos without genetic mutations or by mitochondrial donation, where IVF doctors transfer healthy mitochondria into the embryo to lower the risk of inherited diseases. However, genome editing of human embryos remains controversial, unproven, and risky.
“There is no evidence that editing human embryos is safe,” Greeley said, meaning there is currently “no evidence that it is safe to turn human embryos into Neanderthal embryos.”
Even if a Neanderthal fetus were to grow into a healthy Neanderthal, the life they would face in our world would be excruciatingly bleak.
The only Neanderthals to grow up in the human world of the 21st century would probably be as lonely and isolated as the last Neanderthals in Europe lived. “They won’t have previous generations or peers to learn from,” Ruff said.
And that’s the best case scenario. A darker possibility would be to keep extinct Neanderthals in zoos like animals, Ruff said, which would be abhorrent because “Neanderthals are humans, just another kind of human.”
Greeley said humans don’t have a good track record of caring for others over centuries, so “we’re not confident we wouldn’t be mean to Neanderthals.”
What can we learn from the resurrected Neanderthals?
It’s also unclear what information scientists will learn, given the fact that the world has changed so much in the 30,000 years since Neanderthals went extinct.
“Neanderthals reconstructed in this way will not be living in the past; they will be living in the present in an environment that is neither suitable nor safe for them,” Ruff said. And because we don’t know anything about how Neanderthal genes interact with the environment, we also don’t know how closely reconstructed Neanderthals will physically resemble past Neanderthals.
“It won’t answer almost all the interesting things we want to know about Neanderthals,” Rebecca Wragg-Sykes, archaeologist and author of Kindred: Neanderthal Life, Love, Death and Art (Bloomsbury, 2020), told Live Science.
For example, many researchers are interested in understanding how sophisticated Neanderthal speech was. A combination of anatomical studies, genetic information, and advanced tool technology suggests that they communicated with each other, perhaps without the use of metaphors or abstract language.
Still, Wrag-Sykes said, even if scientists brought back healthy Neanderthals and tried to teach them the language of modern humans, it wouldn’t provide much insight into the language they actually used, just as recovering an ancient musical instrument wouldn’t tell us what songs people were playing on it.
“Neanderthals were a unique and vastly different group, with cultural diversity, culinary diversity, and perhaps linguistic diversity,” Urag-Sykes said. None of the natural background of Neanderthal development can be recreated, so “the shortcuts of cloning or recreating Neanderthals won’t get us there.”
The same logic applies to other abilities. Teaching a recreated Neanderthal how to read and solve algebraic equations would only tell us as much about ancient Neanderthals as experimenting on a single living person and revealing the capabilities of all humans on Earth.
Is it legal to bring home a Neanderthal?
Greeley says it would be highly unethical to resurrect Neanderthals, but the legality of doing so is unclear. This type of human embryo editing is illegal in the US and EU, but it is unlikely that every country in the world has relevant laws in place.
“As far as I know, no one has said it’s illegal to create a Neanderthal,” Greeley said. “Theoretically, if a wealthy person wanted to set up an institute in the Central African Republic that could do this, it wouldn’t be that difficult.”
Other scientists are also concerned about this possibility.
“The extinction of our ancestors could be carried out by private parties at any time,” New York University bioethicist Arthur L. Caplan warned in a perspective essay published in the journal PLOS Biology in September. Kaplan encouraged scientists to start a conversation now that the extinction of Neanderthals and other human ancestors is only theoretical.
Beth Shapiro, chief scientific officer at Colossal Biosciences, was asked if she would form a Neanderthal extinction team in 2024. “Neanderthals were humans. If you’re going to do research on humans, you need informed consent. I don’t know how you would get informed consent from a Neanderthal you want to bring back to life,” Shapiro told StatNews.
But just because Colossal doesn’t seem keen on the idea doesn’t mean other unscrupulous groups won’t do it if it’s legal.
“The extinction of ancient humans should not be left in the hands of private, private, for-profit corporations,” Caplan wrote.
In fact, discovering well-preserved Neanderthal remains may be even more valuable in understanding the culture and living conditions of their extinct cousins.
For example, Ötzi the Iceman was frozen in a glacier in the Alps for 5,300 years. Analysis of his body revealed that he was wearing an animal skin costume, used poisonous ferns to wrap his food, and had dozens of tattoos. The extremely well-preserved remains of a Tollund man who lived 2,400 years ago have been uncovered in the low-oxygen environment of a Danish moor. The analysis revealed that he had been infected with tapeworm, had eaten porridge for his last meal, and had been ritually murdered.
Similarly, “If we were to find Neanderthals in wetlands, like permafrost or swamps, that would tell us an enormous amount,” said Urag-Sykes. “We’ll probably get more than what we get by having a cloned Neanderthal. That’s what I’m more excited about.”
Neanderthal quiz: How much do you know about our closest relatives?
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