Tuesday, October 2, 2012
The first cure for diabetes
Species name: Dahlia x hybrida
Common name: Dahlia
Dahlias are very common ornamental plants in warm temperate (also tropical and sub-tropical) locations around the world. They are native to Mexico, Colombia, and everywhere in Central America between those two countries (we'll see if I can name them all by memory; let me know in the comments if I've missed any! El Salvador, Honduras, Belize, Guatemala, Nicaragua, Panama, and Costa Rica). They were first popularized in Mexico and further south by the Aztecs and Hidalgos that discovered them around 1525. Francisco Hernandez, a European explorer from Spain under the orders of Philip II (he was his physician; clearly physicians weren't so greatly appreciated in the 1500s!), went to Mexico in 1570 and reported back that he had seen these flowers and that they were magnificent. He also reported the use by the native peoples (discussed below), and returned to Spain in 1577 armed with dahlia seeds, leaves, and roots. None of these grew into new plants, and it wasn't until 1789 that they were successfully introduced to Europe Vicente Cervantes after rediscovering the plant in Oaxaca, Mexico.
Ornamental dahlias are a complex hybridization of what is thought to be numerous species. Existing today, there are approximately 30 different species in the genus (and over 20,000 registered cultivars!), but this number is often argued. There is even the suggestion that actually all of the morphological variation can be explained through genome doubling and not different species at all, and so they all belong in one single species named Dahlia variabilis. Once complex DNA studies are done with the members of the genus, we'll have a better picture of how exactly all this variation came to exist. Was it naturally through gene selection in the wild (natural selection) leading to speciation events? Or was it artificially in the lab and in botanical gardens (artificial selection) leading to many varieties and cultivars, but no new species?
Francisco Hernandez is actually an incredibly remarkable man for knowing very little about plants before starting as the personal physician for Philip II (who wasn't the king at the time, he later became King and was so impressed with his personal physician and "naturalist" that he kept him). He was one of the men responsible for taking such incredibly detailed notes about what is now referred to as the colonial-period decline of the population of Aztecs. The cause of this population is still under scrutiny, but Hernandez took incredibly detailed notes about the progression of the disease as well as autopsy results, as he was the main doctor responsible for conducting autopsies until his return to Spain in 1577. He and his son, the one assisting him on his expedition, are the only two men who left accurate reports about the disease. We know that it must have been something that Europeans had previously been exposed to, since no explorers that came in contact with the Aztecs got the disease (and some of them were what we could call "in close contact" with Aztecs if you catch my drift, so it wasn't exclusively a sexually transmitted disease). There are hypotheses about what this disease might have been (smallpox, typhus, plague, dengue fever, yellow fever, malaria, or a combination of two or more of the above; the most well-accepted theory is that smallpox came through first, then a combination of smallpox and typhus), but it managed to wipe out 80% of the population in only 60 years. In equivalent terms today, that would be a disease that could kill approximately 264 million Americans in only one generation. That's an incredible rate of population loss.
Hernandez is credited not only for his medical assistance, but also with his general plant knowledge and discovery. It is estimated that he discovered 600 new species of plants which he published in 24 volumes, one book about animals, one about the minerals of Mexico, and ten volumes of paintings and drawings of plants and animals he discovered on his expedition. He is credited with introducing some of the most important crop species we have in the world to Europe: chocolate, corn, pineapple to name a few, and some of the most important hallucinogenic plants known in human history: peyote and Datura (jimsonweed). He also introduced the drink mezcal (which he called Maguey, the Spanish word for "Agave"), made out of the plant Agave americana, to the Spanish (which you can read all about in one of my previous blog posts HERE).
The historical medicinal uses of the dahlia are numerous. The roots were used by the Aztecs to treat epilepsy, and the long hollow stems were used as water pipes and poison dart launching apparatuses. The most important medicinal application of the dahlia plant is to be the first plant from which inulin was extracted (which was extracted from the tubers; these look very similar to sweet potatoes). This inulin was marketed under the names Atlantic sugar or diabetic sugar, and was used as a type of sugar substitute. Because inulin cannot be broken down by the body into sugar, the symptoms of having too much sugar in your blood were effectively removed. This didn't solve the problem of how to get sugar into the body's cells where it is needed, so better treatments needed to be discovered (and insulin, the key to getting sugar into cells, was discovered in 1923). Inulin is still used as a measure of kidney function today, as the same amount of inulin should exit the body as went into the body (meaning it all has to be secreted by the kidneys; the rate at which it is secreted gives the measure of how effectively the kidneys filter the body's blood).