Monte Verde, such as plants, beach-rolled pebbles, quartz, and tar, indicates possible trade networks and other sites of human habitation of similar age. Academic history Diffusion Awareness about Monte Verde among the international archaeology community was greatly increased in 1989 when Dillehay delivered a presentation on Monte Verde at a conference on settlement of the Americas at the University of Maine. Archaeologist David J. Meltzer notes on that presentation: The images Tom Dillehay was showing of the well-preserved remains at Monte Verde—wooden artifacts and house planks, fruits, berries, seeds, leaves, and stems, as well as marine algae, crayfish, chunks of animal hide, and what appeared to be several human coprolites found in three small pits—were unlike anything most of us, who long ago had learned to be used to stone tools and grateful for occasional bits of bone, had ever seen. Pre-Clovis controversy Because of the nature of the preservation of Monte Verde, it was one of the first Pre-Clovis sites to be accepted by the academic community. Dillehay, himself, doubted his dates due to the stronghold the Clovis First hypothesis has on the academic community. Monte Verde was one of the most accepted Pre-Clovis sites, according to a survey done by Amber Wheat in 2012. Out of 132 respondents (mainly archaeologists), approximately 65% of them confirmed Monte Verde as a Pre-Clovis site. Still, the early date for the site was not widely accepted until 1997. It had hitherto been generally agreed that ancient people had entered the Americas using the Bering Strait Land Bridge, which was about 13,000 kilometers (8,000 miles) north of the Monte Verde site. Though the Monte Verde site does not disprove the Bering Strait theory, it does support the theory that, instead of going down the ice free corridor as previously hypothesized, people may have populated the Americas through a coastal route. A group of 12 respected archaeologists revisited the site in 1997 and concluded that Monte Verde was an inhabited site and predated the Clovis culture. One of Dillehay's colleagues, Dr. Mario Pino, claimed a lower layer of the site is 33,200 years old, based on the discovery of burned wood several hundred feet to the south of Monte Verde. Radiocarbon dating established the wood as 33,000 years old. Dillehay was cautious of this earlier date, and as of 2007 it has not been verified or accepted by the scientific community. Comparison to other