05/30/2012 12:00 pm ET Updated May 30, 2012

Occupy Neolithic: Stone Age Hereditary Inequality Shown In Linearbandkeramik Study

Even the most democratic societies are rife with social and economic inequalities, as the current tension between the poorer "99%" and the richest "1%" vividly illustrates. But just how early in human events such social hierarchies became entrenched has been a matter of debate. A new study of skeletons from prehistoric farming communities across Europe suggests that hereditary inequality was an early feature, going back more than 7000 years ago.

Most researchers agree that social hierarchies began with the advent of farming. The earliest known farming communities are found in the Near East, dating back almost 11,000 years. Archaeologists have looked for evidence of social stratification in these societies with mixed results. Some early farming societies show signs that people played different roles and that some were buried with greater ritual—shuffling off this mortal coil with a number of elaborate "grave goods," including pottery and stone tools. However, there is little evidence that social inequality was hereditary or rigidly defined.

That seems to have changed sometime after farmers moved into Europe from the Near East, beginning about 8500 years ago during a period known as the European Neolithic. One of the best studied farming cultures is the Linearbandkeramik (LBK), which arose in what is today Hungary about 7500 years ago and spread as far as modern-day Paris within 500 years, after which it appears to have been superseded by other cultures.

Archaeologists have long noted signs that the LBK culture might have been socially stratified. For example, some, but not all, males were buried with stone tools called adzes, which were thought to be used to build the wooden houses in which the farmers lived. But a few researchers have argued that this stratification took place only gradually over the 500 year period of the LBK.

To get a better handle on the timing and nature of these social inequalities, a team led by Alexander Bentley, an archaeologist at the University of Bristol in the United Kingdom, analyzed the tooth enamel from more than 300 skeletons from seven LBK burial sites across Europe. These cemeteries, located in the Czech Republic, Slovakia, Austria, and France, ranged from 7400 to 6900 years in age, and covered most of the LBK's territorial spread.

Specifically, the team looked for the element strontium in teeth and measured the ratio of two isotopes, or types of the atom with slightly different weights. Strontium atoms enter the body in the water that we drink and the food we eat, and the ratio of the heavier isotope strontium-87 to the lighter isotope strontium-86 reflects the kind of soil and geological formations a person lived on, particularly as a child, when the tooth enamel was laid down. The strontium isotopes are increasingly used by archaeologists to track movements of populations.

Previous studies have shown that the kind of soil favored by European farmers, lowland sediments known as loess, has a slightly lower strontium-87/strontium-86 ratio than less fertile areas such as upland hills made from granite or sandstone. Yet because of Europe's variable landscape, in which fertile and non-fertile areas can be as close as several kilometers apart, the team relied more heavily on the degree of variation of strontium ratios among the skeletons in a burial site than on their absolute values.

The results of the study, published online today in the Proceedings of the National Academy of Sciences, suggest that men who were buried with adzes—thought to be an indication of higher social status—were more likely to have grown up on loess soils than men who were buried without adzes. For example, among 310 burials the team analyzed, 62 featured adzes. But only one of the 62 skeletons from the adze burials had a strontium ratio in its teeth typical of a non-loess landscape, whereas all of the others were consistent with growing up on loess. Moreover, the variation in strontium ratios between adze skeletons was significantly lower than the variation between non-adze skeletons, suggesting to Bentley and his co-workers that the adze skeletons came from one kind of landscape, most likely loess, while the others came from a variety of other landscapes.

A similarly striking pattern was seen when the team looked at the female skeletons, which made up 153 of the total 311 individuals analyzed. The variation in strontium ratios for females was significantly greater than for males, suggesting that a greater number of females than males had grown up in non-fertile areas. Moreover, the patterns in the male and female burials appeared in both earlier and later LBK settlements, suggesting that the patterns of social inequality were established from the beginning of the LBK period and did not develop gradually over time.

The team came to two main conclusions: First, some males had greater access to fertile soils than others, probably because they were the sons of farmers who had inherited access to the best land. And second, LBK societies were "patrilocal," meaning that males tended to stay put in one place while females moved in from other areas to mate with them. A number of recent genetic studies have shown similar patterns among early European farmers. "The signatures from these skeletons reinforce other indications of male-dominated descent and even land inheritance," Bentley says, adding that such social inequalities "only grew in extent and scale" over the course of history.

Joachim Burger, an anthropologist at the University of Mainz in Germany, says the authors are on firm ground: "The amount of data is huge and the interpretations are straightforward." He adds that the new data, particularly the differences seen between men and women, are "absolutely coherent" with the pattern seen in more recent farming societies, up to the present day.

ScienceNOW, the daily online news service of the journal Science