Complex sentence: To survive the low oxygen levels found at these high altitudes, they must have extra red blood cellsa teaspoon of guanaco blood contains about 68 million red blood cells4 times that of a human.
Split into simpler sentences: To survive the low oxygen levels found at these high altitudes, they must have extra red blood cells. A teaspoon of guanaco blood contains about 68 million red blood cells, four times that of a human.