Monday, November 8, 2010

Life Lines 29


About 50 years ago, during an archaeological exploration of the fortress known as Masada near the Dead Sea, several date seeds were dug up and placed in museum storage. Masada was a Roman fort established during the reign of King Herod. It was taken over by a Jewish sect called the Sicarii in 66 CE. In 72 CE the Roman army returned and laid siege to Masada for about 3 months during which time they built an incline to scale the fort at its easiest access. There is some debate among scholars on whether the Jews committed mass suicide (an act not encouraged by Jewish law) or were destroyed by the Romans. In either case, the Jews did not surrender.

Dates were first domesticated in the mid-East and North Africa about 6000 years ago. Edible dates belong to the species Phoenix dactylifera. Date palms are unusual because the trees are either male or female in their flower anatomy and function. Among cultivated dates (called cultivars) the trees are almost all female, only one or a few being set aside as male trees to pollinate the rest by human hand, usually, although some farms use sprayers to blow the pollen on the female flowers. I’ve seen pictures of wall paintings in Egyptian tombs showing the hand pollination of date palms. When a date seed is planted it takes several weeks to germinate and about 7 years before it can bear fruit. Thus it won’t be until 2013 at the earliest that a single date seed, now a two year old small palm tree, can have its flowers (if a female) pollinated by different cultivars to test its genetic relationship. In the meantime the DNA of the seed (from some of its leaves) has been tested and the original seed components were sampled for carbon 14 dating. The dating showed that the seed came from a tree that was alive about 206 BCE to 128 CE, the most likely being roughly 2000 years ago during King Herod’s reign or just before the destruction of the Jewish communities in Jerusalem.

The DNA analysis used 400 different DNA comparisons between the specimen seed and cultivars from Iraq, Egypt, and Morocco. The least differences (16%) were with those of the Iraqi date trees and the greatest differences (35%) were with those of the Moroccan cultivars.

Spaniards brought dates to Mexico and California in 1765. It is those dates we usually buy in our supermarkets. I greatly enjoy the taste of dates. They have an immense amount of vitamin C but they also have a high oxalic acid content. Alas, I learned a few years ago that my occasional bouts of kidney stones are of the oxalate kind, so dates are now off my regular diet. But as a scientist and historian I cannot but marvel at Linnaeus’s prescience for giving them the apt generic name of Phoenix. As a 2000 year old seed coming back to life from the ashes of Masada, the date has became the oldest known seed to germinate. Its further DNA analysis will teach us much about the history of domesticated plants.

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