On August 6, 2020, the little horse Kurt opened his eyes and took a whiff of air for the first time. Kurt was no ordinary horse though. With his birth, Kurt had rekindled the hope for his species' survival.
What's more significant about this newborn is the fact that his genetic material comes from a vial cryopreserved 40 years ago. The survival of Przewalski's horses native to Central Asian steppes is hanging by a thread.
After WW2, multiple factors including hunting, aggressive human expansion, and a set of harsh winters dwindled their populations. So much so that the last time we saw a wild one was in 1969.
There are some specimens kept in zoos, about 2000; however, there's a fundamental problem with them as well. Between the years 1899 and 1902, 11 wild Przewalski's horses were caught in the wild with another one captured in 1947, all of the 2000 individuals we have on the face of the Earth today are direct descendants of these 12 wild horses. See the problem here?
A dangerous bottleneck
What we see is here is what evolutionary biologists call a "population bottleneck." When a certain species experiences a radical decline in numbers and a subsequent recovery, it can signal the beginning of the end for them.
As you can guess, low genetic diversity is the culprit here. In such scenarios, sometimes certain traits become more pronounced. And the chance of inbreeding increases exponentially, making for a potentially lower likelihood of survival.
While breeders definitely did their best, Przewalski's horses still began experiencing problems. Some were interbred with other horse subspecies to mitigate these while some "pure" born ones were bred anyway. So we had to pick between "purebred" horses with health risks or crossbred ones with low genetic diversity.
This is where a naturally wild Przewalski's horse Kuporovic comes in. This horse which lived between 1975 to 1998 had a wild ancestry from both sides, which means he had more diversity in them than any other known Przewalski's horse. So, scientists took a sample from in and stored it in San Diego Zoo's cryopreservation chamber in 1980.
Recently, San Diego Zoo partnered up with the wildlife preservation group Revive and Restore and a pet cloning company ViaGen Equine to create an exact copy of Kuporovic. The embryo was planted in a surrogate mother, a common horse.
Shawn Walker, the chief science officer at ViaGen Equine reports "This new Przewalski's colt was born fully healthy and reproductively normal. He is head butting and kicking when his space is challenged, and he is demanding milk supply from his surrogate mother."
What this means for other endangered species
This whole deal is not only good news for Przewalski's horses, because this project demonstrates that we can keep genetic material viable for many years. Thus principles we see in action see here can potentially be applied to other endangered, even extinct species. Yes, you've read that right, Revive and Restore hopes to revive a wooly mammoth one day.
Previous studies showed that we can clone bulls from 13-year-old cryopreserved material, or black-footed ferrets from 20-year-old material. It's true that reviving a living being from 40-year-old material kept in a controlled environment and 4000-year-old genetical residue are like apples and oranges, yet they are both fruits. The fact that we can do the former makes the latter seem less impossible.