- Tomatillo, clone of eventing great Tamarillo, reaches 18 months old. Will he compete like his 'dad'?
- Rules changed in 2012 to let clones compete in sport, but experts say focus on breeding for now
- Two clones of Irish sporthorse sire Cruising revealed in February after years of speculation
- Would an Olympic Games with every competitor on a clone of the same horse actually be a fairer contest?
(CNN)To the untrained eye, Tomatillo looks like any horse.
To those in the know, the 18-month-old looks like one horse.
Tomatillo is the clone of Tamarillo -- a famous eventing horse who reached the Olympics in 2004.
Twelve years have passed since humans first successfully cloned a horse. The science is developing fast, but remains imperfect.
The current process takes a sample of cells from a horse's neck, swaps the nucleus of one of those cells into an equine egg, then gives that egg a small electric shock to stimulate development before it is placed inside a recipient mare and carried to term.
Yet Tomatillo, and a handful of others, represent near-exact replicas of sporting excellence and pose an important question: are we going to start seeing clones at the world's top equestrian events?
At the Olympic Games of the future, will a horse compete against itself for gold?
Tomatillo's owners are Finn and Mary Guinness, who also own Tamarillo.
The Guinnesses watched British eventer William Fox-Pitt ride the latter to glory at the Olympics, World Equestrian Games and a succession of other major events until Tamarillo's retirement in 2008.
At that point, there arose a problem.
Like many horses at the top of equestrian sport, Tamarillo is a gelding -- in other words, the horse has been castrated, in the belief that geldings are calmer, easier to handle and therefore more readily prepared for the rigors of competition.
But the decision to castrate the horse is taken well before it's apparent that the horse carries world-class genes.
"When you've finally got your champion, it's too late, because it's a gelding," in the words of Finn Guinness, who brings a learned background to ownership of Tomatillo. Guinness was a one-time student of cloning at Edinburgh University and holds a doctorate in genetics.
His wife, Mary, adds: "When Tamarillo turned out to be this treasure, my husband was regretting it like anything, because he was just interested in keeping the genetics going with the animal.
"And now we can."
A different breed
The Guinnesses have cloned Tamarillo not to replace the horse in the arena, but in the bedroom.
Without a clone, Tamarillo's world-beating genetics would be lost when the horse died. Now, Tomatillo can do the breeding in Tamarillo's place.
"They have the same head, the same personality, the same coloring. It's completely uncanny when you deal with them all the time," says Mary.
"It's especially in the eyes, for me. Looking at the eye, the eye is so similar. They are similar in the way they move, too, and my husband is obsessed with the swirls on his head.
"We are going to try to breed from him, not this year but next year, to see what sort of animals he produces before we go on the open market."
This is in keeping with a broader trend in equine cloning: the focus is on breeding, not sport.
In mid-February this year, two clones of Irish stallion Cruising were revealed.
Cruising died last year at the age of 29. Now, the existence of two clones (Cruising Encore and Cruising Arish) allows his phenomenally successful genes to continue, or so the breeder in question -- Mary McCann -- hopes.
"Cruising would be the number one Irish sporthorse stallion in terms of producing both showjumpers and eventing horses," says Dr Tom Reed, a fellow breeder based in Ireland at Morningside Stud.
Dr Reed says the Irish Sport Horse stud book -- or registry of horses, used by breeders -- "would be very interested in encouraging the owners to clone the horse."
The stud book has struggled to find horses of Cruising's genetic caliber, he believes, and cloning represents a roll of the dice to preserve its greatest equine asset.
Dr Reed sees that as a bad thing. "They're basically counting on 26-year-old genetics to bring the showjumping side of the stud book back into relevance and that's not going to happen," he argues.
Yet for Eric Palmer, that is the joy and purpose of his work.
Palmer founded Cryozootech, in France, in 2001. He has since become a world-leading authority on the cloning of horses, responsible for the cloning of champion showjumpers like ET (one of the first to be cloned) and Quidam de Revel (the first horse cloned in the U.S.)
"The job I'd done before involved technologies for reproduction, like artificial insemination. All the time, the reason for these technologies was giving people a tool to increase their genetic progress," Palmer tells CNN.
"When I saw that cloning was possible, I realized it could be used to make fertile animals out of infertile ones. For me, this is the ability to make a gelding become a stallion."
In 2005, Palmer worked with Dr Katrin Hinrichs, at Texas A&M University, on the cloning of Quidam de Revel.
A decade later, Hinrichs still finds it hard to comprehend why anyone would clone a horse for sport, rather than breeding.
"As a scientist and as a horse owner myself, it never occurred to me that people would want to clone horses to compete them. That's totally sideways," says Dr Hinrichs.
"The reason these horses compete is to show they are really good at what they do, so you can choose the animals to breed to and improve the breed. It's because we want to know which horses are good, so we can choose the stallions and mares we want to breed, so the next generation is better.
"If you compete a clone, what good is that? If the original animal showed great talent, then of course the clone will -- it can't really improve the breed."
And yet some of the advantages are obvious. If you own a champion horse and want to carry on winning medals in future, a clone prolongs your access to that horse's winning genetics for a decade or two. The cost of cloning, at a shade above $150,000, is a fraction of the seven-figure sums routinely spent on champion jumping or dressage horses.
Despite that, Palmer says clients at Cryozootech don't typically have their hearts set on sporting achievement from cloning.
Rewriting the rule book
If they do, his advice is: cloning is not a sure thing.
"Of the few cloned horses starting to compete, Levisto Alpha Z [the clone of Levisto Z], was a champion at four years old in Belgium, showing that clones can do sport," says Palmer. "So it may happen, but it's not really a good reason to make a clone.
"When you clone a big champion, remember he had everything going for him: the best genes but all the rest, too. He formed a good combination with the rider.
"Genetics is only 30%, 70% is other factors. So there's little chance that you will get all 100% of the factors being optimum.
"I would say it's a bet. It's a bet where you have control over 30% of your chances, but you still have 70% that you have not yet controlled."
Not only that, the science does not yet deliver a perfect replica -- as might be implied by the word "clone."