How does the existence of a site like catus hill demonstrate the challenge that archaeologist face when making theories?

Conclusions of archeologists were based on artifacts found over a large area. Exact dates cannot always be determined, and scientists don't always agree on the data provided by the evidence. New discoveries may contradict theories that have already been accepted.

Cactus Hill site has human remains that have been dated to about 20,000 years ago. Due to its location in Virginia proves that human beings had arrived in America earlier than this. That data contradicts the theory that claims that humans reached America from Siberia through the modern day Bring Strait.  

The Cactus Hill Archaeological Site is located on a wind-deposited terrace of the Nottoway River in Sussex County.

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b gas tractor

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c and negotiated lower prices for farm equipment and supplies

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d the grange

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c over 15,000 bankrupt businesses

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c people became more self-sufficient