So there's no one easy way that we know what the date of the pyramids happens to be. The pyramids are surrounded by cemeteries of other tombs. Sometimes we find organic materials, like fragments of reed, and wood, wooden coffins.We find the bones of the people who lived and were buried in these tombs. But primarily we date the pyramids by their position in the development of Egyptian architecture and material culture over the broad sweep of 3,000 years. There are people coming from a New Age perspective who want the pyramids to be very old, much older than Egyptologists are willing to agree.Rarely do we have people from thousands of years ago who are writing, who are signing confessions.NOVA: When it comes to carbon dating, do you need organic material? There has been radiocarbon dating, or carbon-14 dating done in Egypt obviously before we did our studies, and it's been done on some material from Giza.
And as you say, you need organic material in order to do carbon-14 dating, because all living creatures, every living thing takes in carbon-14 during its lifetime, and stops taking in carbon-14 when it dies.NOVA: Can you give us an example of a single aspect of material culture, from ancient Egypt that you might use as a starting point for dating the pyramids? All the pottery you find at Giza looks like the pottery of the time of Khufu, Khafre, and Menkaure, the kings who built these pyramids in what we call the Fourth Dynasty, the Old Kingdom.We study the pottery and how it changes over the broad sweep, some 3,000 years.And you'd work out the different styles in the evolution of Manhattan itself.But by and large, you would, in the broad scope, be able to put the Empire State Building and Manhattan in an overall context of development here in the United States and in the modern 19th and 20th centuries.And you would know that it didn't date, for example, to the colonial period of George Washington and Thomas Jefferson, because nothing you'd find in the Empire State Building ruins, around it, in the dirt surrounding it—maybe it's a stump sticking up above the sloping ruins of Manhattan—nothing really looks like the flowing blue china, or the other kinds of utensils and material culture that they used in the time of the American Revolution.