In the Outlander Season 2 episode titled "Untimely Resurrection" when Jamie and Claire are in France, there is a scene where Jamie goes with the Duke of Sandringham to purchase some horses. In the scene, Jamie inspects a horse's teeth and says, “They claim they’re 3-year-olds, but this one has seen a fair few seasons more.” While not an exact science, inspecting a horse’s teeth can give a fairly accurate estimate of a horse’s age.
Age is determined by inspecting the 12 front teeth called incisors. Like humans, horses have two sets of teeth: “baby” also called “milk teeth” and "permanent teeth."
Age 1 year
All the “baby” or “milk teeth” have erupted. They are smaller, rounder, and have a lighter color than permanent teeth.
Age 2-3 years
The middle, permanent incisors on the upper jaw erupt and will come in contact with the lower incisors at about 3 years of age. Permanent molars have started coming in by this time.
Age 4 years
The canine teeth have erupted and the corner incisors are not in full contact yet.
Special note: Mares usually do not have canine teeth, but stallions/geldings do. Canines are also known as "fighting teeth" and have no benefit for eating.
Age 5 years
All the permanent teeth have replaced the “milk teeth.” The horse now has what is called a “full mouth” and all the incisors are in full contact.
Age 8-10 years
Teeth at this point are starting to show wear and yellowing is present. When the permanent teeth erupted at 5 years, there were cups on the biting surfaces. At about 10 years, the cups on the lower, corner incisors will have disappeared. Cups are still present on the upper, corner incisors.
After 8 years, it becomes more difficult to accurately estimate age.
Age 10 years
The incisors start angling more forward and the upper incisors start to look longer. The teeth will start looking less round and more triangular. A dark groove starts to appear at the gum line on the upper corner incisors called the Galvayne’s Groove.
Age 15 years
The Galvayne’s Groove will reach half way down the incisor. All the cups on the biting surfaces of the upper and lower teeth are gone. Lower incisors start to look shorter than the upper incisors as the teeth angle becomes more acute.
Age 20 years
Galvayne’s Groove will span the whole length of the incisor teeth from top to bottom. The teeth are more angled and look more triangular. They will also be very yellowed.
Age 25 years
The top half of Galvayne’s Groove will have disappeared. The angle of teeth is very steep and teeth look very worn.
Again, inspecting a horse's teeth is not an exact science in determining its age. A horse that has spent much of its life out on pasture and a horse that has been stabled its whole life can have very different looking teeth even if they are the same age. Vets and horse owners take into account the horse's over-all appearance to estimate its age, such as if the horse's hips and spine are starting to protrude or if there is gray hair around the eyes and muzzle.
So, I suspect that Jamie likely saw that the horse had a "full mouth" and the lower and upper incisors were in full contact, indicating that the horse was not 3 years old, but probably somewhere between 5 and 8 years old.
Fun facts: Have you ever heard the phrase, “Don’t look a gift horse in the mouth?" It means to not be ungrateful towards a gift. If someone was given a free horse, it would be rude and tacky to look at its mouth to assess its age and monetary value.
Also, "You're looking long in the tooth," was inspired from an old horse's teeth looking longer than a younger horse's.
Picture drawings are Public Domain and were taken from "The Exterior of the Horse" by Goubaux, Armand, 1820-1890 Barrier, Gustave Harger, Simon J. J
I am Amy. I love movies, TV, and horses. I grew up with horses and taught kids how to ride during my summer breaks from school. Now I am a country girl living in a city hoping to someday move back into a rural area and own a horse again.