The ability of the Mongol hordes to process lactose likely played a significant role in their effectiveness, especially in terms of mobility and logistical advantages over their enemies, such as the Chinese.

Lactose tolerance, which allowed the Mongols to consume and derive sustenance from dairy products, provided a critical dietary advantage. This trait, more prevalent among nomadic pastoralist societies like the Mongols, meant they could rely on their herds for food. The ability to process dairy allowed them to consume milk, cheese, yogurt, and other dairy products, which are rich in nutrients and easily transportable. This was crucial for several reasons:

1. **Self-Sustaining Food Supply**: The Mongols could sustain themselves directly from their herds, reducing the need for extensive supply lines that were vulnerable to disruption. This contrasts sharply with the Chinese armies, which relied heavily on agricultural produce that required more complex and fragile logistics.

2. **Mobility and Speed**: The Mongol reliance on dairy meant they could move rapidly across vast distances without waiting for supply trains. Their horses could graze on the move, and the warriors could consume milk and meat from their livestock, ensuring a consistent food supply without the need to carry large quantities of provisions.

3. **Nutritional Benefits**: Dairy products provided the Mongols with essential nutrients like protein, fat, and vitamins, contributing to their physical resilience and stamina. This high-protein diet likely helped sustain their energy levels and maintain their strength during prolonged campaigns.

4. **Cultural and Tactical Integration**: The consumption of dairy was not just a dietary habit but a cultural norm, which integrated seamlessly into their way of life. This cultural aspect meant that their food sources were deeply embedded in their daily routines and tactical operations, unlike the Chinese, who had a more static, agriculture-based food system.

Historical accounts support these observations. For instance, the Secret History of the Mongols and other contemporary records highlight the Mongols' reliance on their livestock not just for food, but also for transportation and other needs, showcasing their self-sufficiency and adaptability . Furthermore, scholars like Jack Weatherford have noted that the Mongols' ability to harness and utilize their animals for multiple purposes was a cornerstone of their military strategy .

In conclusion, lactose tolerance was indeed a crucial factor that contributed to the Mongol hordes' effectiveness. It provided them with a reliable, mobile, and nutritionally rich food source, significantly enhancing their operational flexibility and endurance compared to their agrarian-based enemies like the Chinese.

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1. "The Secret History of the Mongols," translated by Urgunge Onon.

2. Ratchnevsky, Paul. "Genghis Khan: His Life and Legacy."

3. Weatherford, Jack. "Genghis Khan and the Making of the Modern World."