Battle of the clones: when will a replica horse win Olympic gold?

    Story highlights

    • 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.
      Eric Palmer: "Is cloning the future of breeding? No. I think cloning is one tool among many others."
      "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