Listen to part of a lecture in an anthropology class.

Professor: A critical development in prehistoric societies occurred around 12,000 years ago. That's when the first agricultural societies emerged, when early humans made the transition from being hunter gatherers, hunting animals and gathering edible wild plants into farmers. But what precipitated this kind of transition? OK, so let's consider the Natufians, a prehistoric culture in the Middle East. The Natufians were hunter gatherers who flourished while the region was humid and warm, and therefore supported a wide variety of plants and animals. The Natufians ate mostly wild grains like wheat and rye and some animal meat.

Now, something unusual about the Natufians, since their region was so rich and wild grains, they were able to establish small villages of permanent homes. Other hunter gatherers were more nomadic, following animal herds that migrated seasonally. Now, around 13,000 years ago, climate in the Middle East became cold and dry, relatively suddenly. It was the beginning of a time period known as the Younger Dryas. The Younger Dryas lasted over 1000 years. So how do you think the Natufians would have fared during this period? Student: Um if they depended on plants and animals with colder temperatures? There have been less food. That couldn't have been good.

Professor: There was a decrease in plant and animal life, so you're kind of right there. Natufians did survive the beginning of the Younger Dryas, and there's actually evidence to suggest that it was the hardship brought on by the Younger Dryas that led to the Natufians becoming successful agriculturalists, and ultimately to their survival. Student: So when conditions got worse, it actually helped the Natufians survive?

Professor: The commonly accepted theory is, that as their food sources started disappearing, the Natufians began planting their precious grain. Raising crops insured there’d be a continual food source at a time when it became harder to find grains in the wild. However, there are problems with the evidence, which mostly comes from a Natufian site called Abu Hureyra. Abu Hureyra was occupied early in the Younger Dryas. Researchers there found several large grinding stones, stones they think were used for grinding seeds, stones that are characteristic of agricultural societies. They've also found several rye seeds that may have been cultivated by the Natufians. Student: So how do you know those seeds weren't just, you know, blown in by the wind?

Professor: Well, compared to wild, dry seeds, which are skinny, these were fat. Many researchers think they were especially selected by the Natufians, since plants from these seeds would have produced more grain than wild seeds would have, which would have been critical at a time when the cooling trend was causing hardship. So it’s theorized that the Natufians were domesticating plants, producing lots of grain, and then using the stones to grind it. Student: Oh, but didn't you say there were problems?

Professor: Yes. First, Abu Hureyra is the only Natufian site that contains this kind of seed evidence, and a handful of seeds from one site is hardly a basis for generalizations. And those grinding stones, they could have had other purposes, like um, smoothing animal hides for clothing, say. Another challenge to this theory--when we compare the Natufians to early agricultural societies that are already well documented. Well, A study of gazelle bones at several sites shows that the Natufians didn't change their hunting patterns during the early Younger Dryas. They hunted wild animals as much as always. Yet, from what we know about societies that transition from hunting and gathering to farming, we'd expect the Natufians' diet to show a shift from mostly meat eating to mostly grain eating.

Student: But couldn't those bones mean that as an agricultural society, Natufians were also domesticating gazelles? Professor: No, you see, gazelles require a large range of territory. They also have solitary habits, and they scare easily, all of which makes them hard for humans to control. Prehistoric humans preferred to domesticate animals that naturally gather in herds with some kind of hierarchical organization. One animal acts as a leader and the others fall. This kind of animals easier to domesticate because humans can make themselves the leader of the herd, which is why sheep and cattle are prime examples. And we do find evidence for sheep and cattle raising in early agricultural societies.