The principal difference between wild einkorn and cultivated einkorn is the method of seed dispersal. In the wild variety the seed head usually shatters and drops the kernels (seeds) of wheat onto the ground. This facilitates a new crop of wheat. In the domestic variety, the seed head remains intact. While such a mutation may occasionally occur in the wild, it is not viable there in the long term: the intact seed head will only drop to the ground when the stalk rots, and the kernels will not scatter but form a tight clump which inhibits germination and makes the mutant seedlings susceptible to disease. But harvesting einkorn with intact seed heads was easier for early human harvesters, who could then manually break apart the seed heads and scatter any kernels not eaten. Over time and through selection, conscious or unconscious, the human preference for intact seed heads created the domestic variety, which also has slightly larger kernels than wild einkorn. Domesticated einkorn thus requires human planting and harvesting for its continuing existence. This process of domestication might have taken only 20 to 200 years with the end product a wheat easier for humans to harvest.