TOEFL Integrated Writing

📖 Reading Passage

The domestication of horses is widely believed to have originated on the Eurasian steppes around 3500 BCE, a theory supported by archaeological and genetic evidence. However, a recent hypothesis suggests that horses were first domesticated in the Iberian Peninsula (modern Spain and Portugal) much earlier, around 5000 BCE. Proponents of this Iberian origin theory offer three main arguments. First, they point to the presence of ancient horse bones in Iberian caves dating to 5000 BCE that show signs of bit wear—small enamel fractures on the premolar teeth—indicating the use of bridles. Second, they argue that the genetic diversity of modern Iberian horse breeds, such as the Andalusian, is uniquely high, suggesting a long and independent domestication history. Third, they contend that the Iberian Peninsula had a stable climate and abundant resources, which would have supported an early sedentary human population capable of initiating horse domestication, whereas the steppes were more harsh and nomadic. These lines of evidence, they claim, undermine the traditional steppe theory.

🎧 Listening Lecture

The lecture challenges the Iberian origin hypothesis. First, the bit wear observed on those ancient Iberian bones is not conclusive. Similar enamel damage can result from natural dietary abrasives, such as gritty plant material or soil ingested during grazing, rather than from human-imposed bridles. In fact, studies of wild horse populations show identical wear patterns, so the evidence is ambiguous at best. Second, the claim about high genetic diversity in modern Iberian breeds is misleading. While Iberian horses are genetically distinct, this diversity can be explained by later introductions from North African and Middle Eastern horses during historical periods of trade and conquest, not by an early domestication event. When scientists control for these more recent admixtures, the genetic signal for a 5000 BCE origin disappears. Third, the environmental argument is flawed. The Iberian Peninsula was not uniquely stable; it experienced significant climatic fluctuations during that era, including droughts and vegetation shifts. In contrast, the Eurasian steppes offered expansive grasslands that supported large herds of wild horses, making them a more logical and resource-rich environment for early domestication. Furthermore, archaeological evidence on the steppes—such as horse corrals and milking residues—dates to 3500 BCE, far more solid than the Iberian claims. Therefore, the traditional steppe theory remains far better supported.