JOHN YANG: The northern white rhino was one of the world's biggest land mammals and one of the most endangered only two are known to be alive both female, but scientific breakthroughs are raising hopes for saving the rhino and perhaps even bringing other animals back from extinction.

This report is part of our series Saving Species.

JOHN YANG (voice-over): With the last known male northern white rhino in existence, named Sudan died in 2018 it seemed the future of the entire species died with him.

Like many endangered species, their population has been devastated by human activity, widespread poaching and civil wars and their native Central Africa.

Today, only two females remain Najin and Fatu, both living in a conservancy in Kenya.

But a recent scientific breakthrough has raised hopes for the northern white rhinos survival.

THOMAS HILDEBRANDT, Leibniz Institute For Zoo and Wildlife Research: The shift together, something which was not believed to be possible.

JOHN YANG (voice-over): Thomas Hildebrandt leads a team that successfully implanted a rhinoceros embryo into a surrogate mother.

Until now a tricky proposition giving the rhinoceros is two tongue size.

The embryo and mother were southern white rhinos, a close relative of the Northern subspecies,.

THOMAS HILDEBRANDT: What we have to do is mimicking nature, and to learn from nature and mimicking it and that worked quite well.

And I never lost my task that we will be successful.

JOHN YANG (voice-over): Now the team plans to use northern white rhino eggs and sperm that was harvested years ago from living male rhinos to continue the species because of age and health problems neither Najin or Fatu were able to carry pregnancies, which lasts about 16 months.

So the embryos will again be carried by Southern white rhinos.

Hildebrandt hopes a female can give birth to a calf within the next two years in order to preserve a crucial element that can't be replicated in a lab.

THOMAS HILDEBRANDT: If you want to save this social heritage, and therefore we need to let a calf which can learn the language from this last tool of their kind.

The genes are important, yes, but behavior is something which also needs to be conserved.

Otherwise, you're -- you end up as a nutrient, an animal that does not know what it actually is.

JOHN YANG (voice-over): But the northern white rhinos conceived this way won't have the genetic diversity needed to sustain a healthy population.

So Hildebrandt and his team are working with a US based genetic engineering firm called colossal Biosciences to use stem cells and gene editing technology to bridge the gap.

THOMAS HILDEBRANDT: If you want to introduce these individuals to the wild, they should have a wide variety of genes to fight against diseases, environmental factors, so there should not be an in breeding group.

That should be a healthy genetic population, but it's a quite holistic approach, which will take maybe decades to fulfill it.

However, it is a very pioneering concept, which gives a lot of hope for typical endangered species.

JOHN YANG (voice-over): Other scientists using genetic technology in an attempt to reintroduce or de extinct the dodo bird, the dodo was first seen around 1600 on the island of Mauritius in the Indian Ocean.

It became extinct less than 80 years later due to deforestation, hunting and destruction of their nests by animals introduced by Dutch settlers.

Beth Shapiro has spent 25 years studying the dodo.

She's an evolutionary biologist at the University of California, Santa Cruz, and an advisor to colossal biosciences.

BETH SHAPIRO, University of California, Santa Cruz: I became increasingly captivated by trying to figure out what it was about the dodo that made it so susceptible to becoming extinct, but also really to learn more about this iconic species so that we could potentially just really bring more attention to the fact that people are causing extinctions today.

JOHN YANG: Shapiro says the reintroduced dodo won't be exactly the same as the pre extinction birds.

BETH SHAPIRO: Identical copies of things are never going to happen.

But that's not the way evolution works anyway.

If we think about de extinction in a logical, ethical, ecologically sustainable way, it can't be this purist ideal of what the extinction means.

Instead, it has to be this creation of something new that's adapted for the for the habitat of today, and yet can potentially fill this, this void.

JOHN YANG: In 2000, Shapiro took DNA samples from the only known surviving soft tissue of a Dodo, housed in Oxford University's Museum of Natural History.

That led to the discovery that the dodo's closest living relative is the Nicobar pigeon, found in parts of Southeast Asia.

Using another dodo DNA sample from Copenhagen's natural history museum, Shapiro and her team were able to announce in March 2022, that they had sequenced the dodo's entire genome.

BETH SHAPIRO: If we want to know what makes a dodo unique, we have to have the whole nuclear genome sequence, the whole genome sequence, which we can then line up next to the genome sequences from other birds on a computer and start to look for the differences between those genomes.

Because of the intricacies of the bird's reproductive system, one cannot clone birds.

So one of the greatest technological hurdles in resurrecting a dodo will be to come up with some other way.

JOHN YANG (voice-over): The Nicobar pigeon will provide the host cells and the genome for engineering.

BETH SHAPIRO: An important step because we can't make millions of changes in a cell if we're going to change Nicobar pigeon cell to being a dodo cell, is to figure out which of those millions of differences are actually important to making a dodo look and act like a dodo.

JOHN YANG (voice-over): Why are scientists making all this effort to resurrect extinct animals like the dodo and propagate threatened species like the northern white rhino?

BETH SHAPIRO: We are in the midst of an extinction crisis.

And we should be looking for all of the different potential tools that might be out there for us to be able to help species that are alive today and in danger of becoming extinct to avoid that fate.

These tools that we will develop on the path to de extinction have immediate application to modifying the genomes of species that are alive today, potentially to help these organisms adapt to the rapidly changing habitats.

THOMAS HILDEBRANDT: They are at the brink of extinction, not because they lost an evolution.

Because of us, because of human activity.

We poach them down to extinction.

We destroy their habitats, and I think science can provide a newer alternative we have to live in harmony with nature, and we have to make responsible decision how to exploit to the sources and restore the sources otherwise, there is no science which can save the human civilization.

JOHN YANG (voice-over): Trying to undo some of the harm of human activity.