Ancient Horse DNA Shows Scythian Warriors Were Adept Domesticators
A Mongolian horse breeder catching horses. Credit Ludovic Orlando/Natural History Museum of Denmark/Centre National de la Recherche Scientifique
Horses sacrificed by fierce nomads living in Central Asia more than 2,000 years ago have provided new insights into how people tamed the wild animals and bred them to their needs.
The Scythians roamed over a vast swath of this region, from Siberia to the Black Sea, for about 800 years beginning about the ninth century B.C. They were known for their equestrian battle skills, including the ability to shoot arrows while riding, and for the brutal treatment of those they defeated. Herodotus, an ancient Greek historian, wrote that the Scythians blinded their slaves, and the warriors drank the blood of the first enemy they killed in battle.
In a study published Thursday by the journal Science, an international team of researchers deployed the latest genetic tools with 13 stallions that were buried in a mound in what is now Kazakhstan, well-preserved in the permafrost. (The Scythians appear to have only sacrificed male horses.)
The decoded DNA not only provides insights into the ancient horses, but also suggests the Scythians were more than warriors.
“Here we see them as breeders,” said Ludovic Orlando, a professor of molecular archaeology at the University of Copenhagen in Denmark, who led the research. “We reveal part of their management strategy and part of their knowledge 2,300 years ago.”
The findings also fit an emerging theory of how domestication in general changes animals as they become intertwined with humans.
“It’s great stuff,” commented Greger Larson, director of the paleogenomics and bioarchaeology research network at the University of Oxford in England, who was not involved in the research. “It demonstrates the power of ancient whole genomes to understand the pattern and the process of domestication.”
Among the farm animals whose lives have become entwined with people, horses were a late addition.
Dogs were the first animal friends of humans — wolves that scavenged for food among garbage piles and turned docile about 15,000 years ago, or possibly much earlier. Cattle, chickens and pigs were domesticated by people in different parts of the world between 8,000 and 11,000 years ago.
It was only about 5,500 years ago that people in Central Asia started catching and keeping wild horses for meat and milk. Riding horses came later.
In the new research, the scientists used a bit of bone from the horse skeletons — less than half a gram in most cases — to extract DNA. They were able to decipher the genomes for 11 of the 13 horses from the Scythian mound. They also analyzed the DNA of two stallions from a royal Scythian tomb 400 years earlier, and one mare, dating to 4,100 years ago, that belonged to a nearby, earlier people, the Sintashta, who had already figured out how to use horses to pull two-wheeled chariots.
The site of a royal Scythian tomb where scientists assessed the DNA of two stallions. Credit Michael Hochmuth/German Archaeological Institute, Berlin
From the DNA, the scientists found that the Scythians bred for certain characteristics: stockier forelimbs that were thicker. The horses also had genes for retaining water, perhaps indicating that the mares were milked for human consumption. Many, although not all, of the horses possessed genes associated with racing speed that are found in today’s thoroughbreds.
The genes also showed a variety of colorings — cream, black, spotted, bay and chestnut.
Many of the genetic changes were related to the “neural crest” — a line of cells along what becomes the spinal cord during embryonic development, but which migrate to various parts of the body. That fits in with an idea proposed in 2014 of how domestication and the initial goal of breeding tamer animals able to live and work with people also led to a series of other traits commonly observed among domesticated animals: smaller brains, floppy ears, curly tails, varied colorings.
“Most of them have a neural crest derivation,” said Adam S. Wilkins, a visiting scientist at Humboldt University in Berlin and one of the authors of the hypothesis.
The genetic changes may slightly reduce the number of neural crest cells, and that may lead to smaller adrenal glands, which produce “fight-or-flight” hormones. The result may be animals that are less likely to startle, and are more amenable to being handled by people.
“This begins to support a sort of grand unified theory of domestication,” said Daniel Bradley, a professor of genetics at Trinity College Dublin in Ireland.
What the researchers did not find is the gene that enables certain horse breeds today to “amble” — a gait that is faster than a walk but slower than a gallop.
Unlike modern horses, the Scythian horses’ DNA showed no signs of inbreeding. “This is extremely surprising in horses,” Dr. Orlando said.
The Y chromosome tells the genetic story of males of a species. The mitochondria — energy factories within cells — contains DNA passed down only from mothers. In modern horses, the Y chromosomes in stallions are almost identical, reflecting the breeding technique of using a single stallion with desired characteristics to father many offspring.
That indicates that the Scythians maintained the natural herd structure of horses, Dr. Orlando said. He said additional studies had revealed when and where the genetic diversity of stallions crashed later, but he would not say publicly until he finished the scientific paper that laid out the answer.
For Melinda Zeder, a Smithsonian Institution scientist who studies domestication, that fits in with other research that indicates the narrow genetic variation among many domestic animals — which sometimes leads to prevalent diseases — is a recent development, not an inevitable consequence of domestication.
“I think that’s a very important lesson for the future,” she said. “A red-flag warning we would do well to pay attention to.”
The findings also point to the profound impact that humans have had on the environment and the evolution of other species for millenniums. “It is something humans have been doing for a long time,” Dr. Zeder said. “It’s not always detrimental.”
Vikings Possibly Spread Smooth-Riding Horses around the World
The New York Times by STEPH YIN AUG. 10, 2016
An ambling Icelandic horse. Credit Raimund Franken/Getty Images
This week, equestrian athletes at the Rio Olympics are competing in an event called “dressage,” in which they guide their horses to perform complex combinations of different gaits, including the walk, trot and canter.
One type of footwork (or hoofwork, if you will) you likely won’t see is an “amble,” a sometimes comical four-beat gait that’s faster than a walk, slower than a gallop and well-suited for smooth, long rides.
Icelandic Horses Championships in Berlin, 2013 Video by Kristján Sigurjónsson 3 min.
Most horses can walk, trot, canter and gallop, but only certain breeds can amble. In a study published on Monday in Current Biology, scientists have proposed a hypothesis for how horses with this ability came to be found around the world. They suggest that ambling horses arose in Medieval England and then were brought to Iceland by Vikings, who subsequently spread the animals across Eurasia by trade.
The study is a follow-up to the discovery in 2012 that the ability to amble can be traced to a single gene mutation. It’s called DMRT3 or, colloquially, the “gaitkeeper” mutation.
In the new study, the researchers analyzed DNA from the remains of 90 ancient horses. They found the gaitkeeper signature in horse samples from England dating back to the 9th century. They also found the mutation in early Icelandic horses from the 9th to 11th centuries. When they looked at horses from the same time period in mainland Europe, however, they failed to find the gene.
In the 9th century, Vikings occupied parts of England that had ambling horses, said Arne Ludwig, an evolutionary geneticist at the Leibniz Institute for Zoo and Wildlife Research in Berlin, and an author of the paper.
He believes Vikings pillaged English horses and sailed to Iceland with them. There, horses with the ability to amble became dominant as people bred animals that were easy to ride for long distances across terrain without roads.
Icelandic horses like these may have been pillaged by Viking raiders in the 9th century. Credit Cuveland/Getty Images
When Vikings brought these horses to trading destinations as far as the Middle East and the Caspian Sea, others possibly recognized the advantage of ambling horses and started to breed for the trait. “You have a fast and comfortable ride with these horses,” Dr. Ludwig said. “It’s a huge improvement compared to horses without this mutation.”
“This study is a good example of how horse and human history are inexplicably intertwined,” said Samantha Brooks, a professor of horse physiology at the University of Florida who was not involved with the study. “The success of the Vikings in a climate as challenging as Iceland was no doubt in part due to the advantage that the use of these horses gave them.”
The Viking story is the best interpretation of current data, but it’s still plausible that ambling horses were bred earlier than the 9th century, said Leif Andersson, a professor who studies the genetics of domestic animals at Uppsala University in Sweden, and an author of the paper.
It’s possible that the mutation “arose in East Asia and then spread westward,” he said, noting that some Chinese horse sculptures from nearly 2,000 years ago seem to depict an ambling gait. “We need more extensive sampling.”
Lindsay Blatt and Paul Taggart joined forces to shoot a documentary about Iceland's unique horse breed and its independent people.
By Lindsay Blatt and Paul Taggart on Publish Date June 25, 2012.
Today, ambling horse breeds exist around the world — there’s the Missouri Fox Trotter from the United States, the Campeiro from Brazil, the Aegideinberger from Germany, and the Marwari from India, to name a few. In all these horses, the gaitkeeper mutation controls the expression of genes in certain neurons that coordinate muscle movement.
Horses with the gaitkeeper mutation can amble, or move at an intermediate pace with usually only one hoof off the ground at a time, but they have trouble transitioning from a trot to a gallop — which is why you don’t tend to find them in the Olympics.
But, if you go horseback riding and you’re a novice, there’s a good chance you’re riding an ambling horse. If that’s the case, consider thanking the Vikings.