My next review is of Horses: A 4,000-year genetic journey across the world by Ludovic Orlando (translated by Teresa Lavender Fagan).
It is a product of the work that the author did as the leader of a team of scientists and archaeologists on the evolution of the domesticated horse. The core of this work was to sample horse remains over a wide span of time for DNA to identify where horses were domesticated and how they evolved over time. The book is scattered with vignettes of the scientists and archaeologists with whom he collaborated.
There are eleven thematic chapters, covering the origin of the domesticated horse, the origins of horses in different parts of the world, mules, and horses in different periods of time.
It is worth remembering that a little over 100 years ago horses were economically critical, an outbreak of equine flu had a huge impact on the US economy in 1872/3 since much transport of goods and people was by horse. Indeed the severity of the Boston fire is attributed to the inability to move water pumps because of a lack of horses. Globally the number of horses has declined to around 60 million since the end of the 19th century when it was probably around 75 million but against the background of a human population that has tripled in that time.
The genetic work shows that the origin of the domestic horse is relatively recent – dating to 4200 years ago in the Volga-Don valley bordering the Caspian Sea north of the Caucasus – very close to the part of Ukraine that Russia has recently invaded. All modern horses are descended from this domestication with the exception of the wild Przewalski’s horse which are descended from an abortive earlier domestication in the Botai culture of Northern Kazakhstan. Here the horse had been domesticated a little earlier , approximately 5000 years ago, as evidenced by archaeological remains, but no trace of these horses is found in modern horses (aside from the Przewalski’s horse). Prior to the genetic work the location of the domestication of the horse was uncertain, options covered central Europe and Asia, as well as the Iberian peninsula. It was believed that Przewalski’s horse represented a truly wild horse. Orlando covers pre-domestication horses in a separate chapter but does not go into the textbook evolution of the horse from eohippus.
The domestication of the horse relatively recent compared to other animals. Genetically domesticated horses have two key differences from their wild ancestors, they are more docile and have stronger backs.
Once domesticated the horse spread rapidly across Eurasia, there is a chapter here on whether the Indo-European language group spread simultaneously with the horse but the evidence is that agriculture and language spread before the horse was domesticated but that there was an acceleration around the time of its domestication. Orlando suggests that the key feature of the horse was its ability to carry loads, and that drought in the cradle of its origin drove the migration. It had previously been proposed that the horse had spread via its use in raiding and war-fighting.
Genetics are central to the whole book but don’t really get a consolidated explanation anywhere, I suppose because the details are quite technical and for the reader the key thing is the outcome – for example measuring relatedness and identifying the function of genes which have been selected by breeding. I was curious to learn of the ambling gait for horses, and its origin in a single gene, DMRT3. This is found is specific breeds such as the Icelandic Horse, Peruvian Paso and the Tennessee walking horse. I found the text descriptions of gaits confusing but there are plenty of videos online illustrating the ambling gait, it looks unusually smooth at faster paces.
As soon as humans start domesticating horses the population of horses starts to rise dramatically, human breeders break the rules of the equine social order which greatly increases the breeding capacity. The control breeders exert is even more marked nowadays in the breeding of racehorses. They all have the same notional birthday (1st January in the northern hemisphere) which means that there is a benefit to arranging the birth of foals as close after this date as possible since horses are raced very young and classed by age.
I found the chapter on modern racehorses a bit depressing, the death and injury rates for racehorses particularly in the US is high. Furthermore, genetic defects are persisted deliberately because they confer an advantage in racing the young horse.
There is a chapter on mules, once highly regarded and prestigious both for their “hybrid” vigour and also and their relative scarcity – mules are infertile so they can only be bred directly from donkeys and horses. They were particularly popular with the Romans for use in carrying goods. Also mentioned is the kunga a donkey-onager cross highly valued by the ancient Egyptians.
The chapters on different times and places focus on what we might be able to say about the characteristics of horses from that time or place, so we learn that Medieval war horses were surprisingly small, and that paler horses declined in numbers after the 5th century. The exception to this is the horse in America where the question of whether any of the horses in US have an ancestry outside that originating in Europe – the answer is that they don’t although Orlando talks about their being more work to do in this area.
The book finishes with a chapter on cloning. I was surprised to discover that Argentina seems to have taken the lead on this, cloning polo horses – it has been rather more successful than I expected.
In the epilogue Orlando talks about learning to ride at the age of 42, after he had done the majority of the work in this book!