According to the professor, what crop was NOT cultivated by the ancient inhabitants of the Norte Chico region?

Listen to part of a lecture in an archaeology class.
Professor: If I asked you to name an ancient civilization from Peru, many of you might say the Incas, but let’s consider instead the impact of a mysterious culture from North Central Peru that thrived in a collection of valleys called the Norte Chico region. Archaeologists have been finding evidence that suggests that Norte Chico is a region where the early inhabitants of South America first began a pivotal transition from being hunters and gatherers and formed a complex and substantially developed society. This would be around 3,000 BCE, well before the Incas even existed. These sites were so advanced that nothing like them could be seen anywhere else in the Americas at the time. There’s no official name for the culture yet, but it seems that its architecture and developments had a profound influence on subsequent cultures in the Americas for thousands of years afterward.
    At each site, archaeologists have identified one or more enormous platform mounds, sort of like rectangular, terraced pyramids. Throughout the whole region, people were organized enough to plan and produce these large, terraced pyramids, something the Americas had never seen before, and each of the sites apparently served as a residential center, so people lived and worked there. It seems they were farmers. Now, this collection of over 20 residential centers is very exciting for a number of other reasons as well. For one thing, their existence has called into question a previous theory about how complex society emerged in the Americas. You see, in the 1970s and 80s archaeologists had examined the coastal site in Peru called Aspero. Aspero was one of the first of these sites in Norte Chico to be discovered and studied extensively. That was about 40 years ago. It’s directly on the coast and it has these same mounds dating from the same period, about 3,000 BCE. It is believed that Aspero was a fishing village, and based on this fact, archaeologist concluded that the first complex society was based on and sustained by ocean and marine resources without agriculture. They didn’t know yet though that Aspero was just one of many such sites in the region, and most of these other sites were inland, quite a distance away from the coast, but now we know that all these inland sites exist and that they were built around the same time.
    Another exiting thing about this recent research is that it calls into question some long held assumptions about how complex societies develop. You know when we work with any ancient society and consider its classification, a standard traditional hallmark used to classify the culture as complex is the presence of ceramic pottery. The other major birthplaces of complex civilization around the world like Egypt or Mesopotamia, they all had pottery, but did this mysterious civilization provide us with evidence of any ceramic pottery? The answer is no. This culture is unconventional in that respect.
    Researchers have also discovered botanical remains of domesticated plants, including cotton, squash, chilies, beans, and avocadoes, but interestingly they found almost no evidence of preserved corn or other grains. This means that this early culture developed not only without pottery, but also without a staple grain-based food, which is usually the first large-scale agricultural product of complex societies, so here again the ancient Peruvians took a different path to civilization. Additionally, in one specific archaeological site Caral, they uncovered artifacts called ’quipu.’ Essentially, a quipu’s an intricate collection of hanging strings, cotton strings of many colors. Each quipu contains an elaborate combination of color and design that communicates meaning. Each one has a wide variety of special intricately tied knots. People transmitted information in this manner. There was meaning associated with the color selected, the knot used, the fiber chosen. There are even those that speculate it may have been a writing system.
    Interestingly, the 3000 inhabitants of this one particular city Caral, appear to have left. You may be asking why. Well, here’s what we know: there doesn’t appear to be any evidence of an invasion from outside enemy forces; there’s no sign of rebellion from the people who lived there. What we see instead is an orderly process whereby the occupants covered the buildings with substantial amounts of gravel and pebbles and then were gone.