Listen to part of a lecture in an archaeology class.

Professor: As an archaeologist, I'm often asked, how do we know where to start digging? There are many answers to that question. We can search historical records for descriptions of where towns or settlements used to be. We can walk across areas looking for surface clues like pot sherds or evidence of an ancient fire hearth.

One high tech approach is aerial surveillance, gathering data from heat sensing scanners aboard airplanes. Some buried archaeological features leave invisible thermal signatures and are too large to be detected at ground level. There are also excavations prompted by chance discoveries like the Dead Sea Scrolls, written more than 2,000 years ago. The first Dead Sea scroll fragment was found in a cave by a shepherd chasing after his animals. Sometimes we are guided to an archaeological site by a construction plan. Like here in the United States, starting in the late 1940s, there were numerous large scale construction projects.

Professor: Ok, is anyone studying modern US history? What happened around that time? Think transportation. Student: The highway construction projects? A lot of interstate highways got built back then. Professor: Not just highways, but dams, too. Archaeologists knew that as a result of building dams, artificial lakes would be created submerging large swaths of land, land that was possibly inhabited by ancient peoples. So, if archaeologists want to excavate these areas, we must do so before construction begins. Rachel?

Student: So, what do archaeologists do? Just show up and tell the construction crew to make sure there aren't any pot sherds around？ Professor: It's much more carefully orchestrated than that. Major road and dam projects are publicized well in advance. And since they're funded largely by the government, there's money earmarked lots of money for what's called rescue archaeology.

Student: Oh, did rescue archaeology include those archaeological projects funded by the WPA? Professor: You mean the works progress administration? Student: Yeah, the works progress administration. I know those WPA projects were done in the 1930s during the Great Depression when millions of people needed jobs.

Professor: Please don't confuse rescue archaeology with the WPA’s excavation. You might remember from history classes that the WPA was a government funded program to create employment. And one of those efforts was a series of archaeological digs all across the country. Unfortunately, people hired to do those excavations often were not very well trained and didn't always interpret their findings properly.

Rescue archaeology, on the other hand, is carried out by qualified archaeologists using strictly scientific methods. In fact, rescue archaeology didn't even get started until after the Great Depression in the 1940s and 50s. But while rescue archaeology is scientific, it's not without its critics. Does anyone remember what your textbook says about that?

Student: Yeah, it says rescue archaeology gets initiated in response to construction projects that have specific timelines and deadlines. So, the archaeological works supposedly done in a hurry. Professor: Right. Critics worry about rushed work, which could conceivably result in sloppy data gathering. In truth, however, archaeologists usually get plenty of notice to carry out a well-planned, well-designed excavation.

Student: So, what kinds of sites have they found? Professor: In the U.S. the sites generally fall into two categories, Native American settlements and artifacts, and prehistoric sites like fossil deposits. In New Mexico, for example, researchers uncovered several Native American houses from different time periods along with tools and other artifacts. There are also many sites in the Midwest like Wildcat Hills, Nebraska. If you fly over Wildcat Hills, you can see how barren it is. A few years ago, the government was planning a highway expansion, so they called in archaeologists who searched the area for fossils and found some interesting things. Like the gravel there came from mountains, hundreds of kilometers away. This suggests that at one time, there must have been a major river in the region that would have carried that gravel to Wildcat Hills.

Archaeologists also found enough petrified wood to infer that this barren area used to be heavily forested. And there were all kinds of fossils, including camel, deer, bear, and most importantly, newly discovered species. Finds like this without rescue archaeology, these discoveries might never have been made at all.