Let's Talk About Science: Sailing The Vitamin C

Centuries ago, during the age of exploration, seafarers on long voyages were afflicted by a terrible illness. Fatigue, bleeding gums, personality changes and eventually even death could strike the victims. This scourge of the sea was scurvy, a condition caused by lack of vitamin C. Eventually, sailors took to carrying citrus fruits on long voyages and, in one of the few examples of effective cures of the day, rid their vessels of the dreaded disease.

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Most animals produce vitamin C internally and don’t need to consume it in their diets to survive. Humans, along with several other primates, are some of the only animals that have lost the ability to produce their own vitamin C. There’s no obvious benefit to losing this ability.

This genetic trait can cause scurvy, which would seem like a major evolutionary disadvantage. In fact, had the same gene mutation occurred in other animals whose diets don’t include a lot of vitamin C, the individuals carrying the broken gene would most likely lose their struggle with natural selection.

The mystery becomes clearer when we consider the diets of tropical primates like our early ancestors. These primates have large amounts of fruit in their diets and therefore have an abundance of vitamin C provided in their food. It follows that individuals could lose the ability to synthesize vitamin C but not be eliminated from the gene pool.

Since there isn’t a selective pressure one way or another, effects such as genetic drift take over. This effect describes how gene variants may take over a population due to random fluctuations in reproduction, even without a driving evolutionary force. Genetic drift is seen in populations of various species throughout the world and is thought to play a significant role in the development of new species.

It seems fitting that as the first species to invent boats, we are genetically adrift, sailing in the vitamin C.