Before the Romans, however, a city needed a hill for defense, with a spring nearby. Certain proportions had to be right: the hill had to be small enough so that the population supplied by the spring would suffice to produce enough soldiers to defend a wall surrounding the hill. You needed enough good agricultural land to feed that population. (You also needed peasants in nearby villages to work the land: about ten for every aristocrat in the city.) If you wanted to engage in commerce, you had to be near a decent road.

Only certain hills fulfilled these requirements, and therefore people kept building on them. That is why we find layer after layer on some few hills, called tells,  while others remained unsettled.

People usually built with mud brick on stone foundations. When destruction came, the walls would collapse, leaving a layer. In distinguishing a layer and its contents, archaeologists refer to it as a stratum. At Megiddo, for example, the American team counted twenty major strata.

Among the items that appear in a stratum are usually many fragments of pottery. Invented around 6000 BC, pottery fulfilled the function that plastic or metal containers do today. Digging through a tell (that is, through time) we find fragments showing different materials, styles and techniques. The decoration, in particular, enables deductions about the lives of the makers. Webster, for example, has demonstrated parallels between the Geometric vases of ancient Greece and the structure of Homeric epic.



It is an advantage for dating that pottery easily breaks: it does not usually get passed through the generations (though whole pots are often preserved in tombs). In digging down through a tell, therefore, we can distinguish layers with ceramic fragments that vary in the material, style and technique of their making. We can map out the sequence of layers, sketching the different types of pottery found in each. We can then go to another tell nearby, do the same, and we shall likely come up with a similar sequence.  By comparing many tells in a specific region, we can gain an ever more precise idea of what kind of pottery came after what.

That is the principle, but of course things are never so simple. A city starts out on different levels. Stones are reused. People fill pits or dig new ones, disturbing the layers. New houses are built beside older walls. Some pots continue to be made or imported through several periods. In a word, the vicissitudes of life disturb the regular accumulation of layers. Nonetheless, as tell after tell is explored and recorded, knowledge of the sequence improves.

All that, however, gives at best a relative chronology: we know that a pot of type Y came after a pot of type X. We want, however, to be able to anchor the strata to absolute dates. We want to be able to say, for example, "Here is a stratum from the time when Solomon reigned."

How can we arrive at absolute dates? There are two major methods, each with its problems.

First, within the layers archaeologists sometimes find items with the names or symbols of Mesopotamian kings or Egyptian pharaohs. Such items may be statues, inscriptions or scarabs. But these do tend to be handed down as heirlooms; we can hardly ever be sure that we have found them in the stratum of their origin. Often they appear in obvious secondary use, as part of a wall, for example.

If we knew for sure that a particular king or pharaoh ruled between 970 and 930 BC, and if we were to find many pottery fragments containing his name in a particular stratum, we could then assert that such fragments, along with any others found uniquely in the stratum with them, date from those years. On finding similar fragments in the stratum of another tell, even without the inscriptions, we could then say that this stratum too must be dated between 970 and 930 BC. In theory that works, but it just hasn't happened.

There are problems, besides, in determining when the kings and pharaohs lived. There is no sure chronological anchor until the 8th century BC in Assyria. The Assyrians "kept 'lim-mu' lists, which for each year state the name of the highest-ranking official in Assyria, sometimes together with an important event that took place at the same time. The limmu lists known run from 911 through 631 BC. The lists can be dated with the aid of the Canon of Ptolemaeus (second century AD), and coincide with dates from the Canon between 747 and 631 BC." (van der Land. ).

This Canon lists Babylonian kings, but among them are some Assyrians who claimed authority over Babylon, for example, Sargon II. In a mathematical work, the Canon presents astronomical data, including solar and lunar eclipses, and connects them with particular kings. These data check out well against astronomical observations recorded on baked clay tablets found in Babylon.

According to one limmu list, a solar eclipse occurred in the tenth regnal year of the Assyrian king, Assurdan II, in the month of Sivan (May-June). Using the Canon of Ptolemaeus, scholars date that king's tenth year to 763 BC. On purely astronomical grounds, modern scientists have computed that there was in fact a solar eclipse on June 15, 763 BC. Thus we get an absolute date, a chronological anchor, for Assurdan II, and thanks to the detail of the limmu lists, we can extend our confidence to the kings after him, down to 631 BC. The Assyrians took the Egyptian city of Thebes in 664 BC, so from this time the firmness extends to Egypt as well. What is more, in the 6th century BC, coins began to circulate widely; these often contain data enabling researchers to determine the date of their minting.

But what about the period before 763 BC? Here archaeologists have largely depended on Egyptian chronology, which until recently was thought to be well established. In the last decade, however, challenges have arisen. The trouble is, one has to be an Egyptologist in order to decide between rival hypotheses, and being an Egyptologist does not leave time, apparently, for being anything else. If the conventional Egyptian chronology is off by a hundred years (some say as many as 250!), the list of pharaohs may slide with respect to the list of Biblical kings. At present both lists are afloat. The hope of getting absolute dates for strata (the hope of saying, for example, "Here was the city of Solomon's day") recedes.

For anyone who wants to take a dip in the recent debates on Egyptian chronology, here are a few Web sites for starters. Surfers beware! Strong undertow!

1. Centuries of Darkness by Peter James, IJ Thorpe, and others. Another site.

2. A Test of Time Home Page. The Official David Rohl Website.

3. J.G. van der Land, "Pharaohs and the Bible:  David Rohl's chronology untenable" 

4. P.G. van der Veen, "Is Rohl's chronology inaccurate?"

5. Jonathan Wade, Waste Of Time Home Page