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granted, quipu are not referred to in this article, but age appears to be established:

http://www.philipcoppens.com/caral.html

Caral is indeed hard to accept. It is very old. Still, its dating of 2627 BC is beyond dispute, based as it is on carbondating reed and woven carrying bags that were found in situ. These bags were used to carry the stones that were used for the construction of the pyramids. The material is an excellent candidate for dating, thus allowing for a high precision.
The town had a population of approximately 3000 people. But there are 17 other sites in the area, allowing for a possible total population of 20,000 people for the Supe valley.
All of these sites in the Supe valley share similarities with Caral. They had small platforms or stone circles. Haas believes that Caral was the focus of this civilisation, which itself was part of an even vaster complex, trading with the coastal communities and the regions further inland – as far as the Amazon, if the depiction of monkeys is any indication.

For an unknown reason, Caral was abandoned rapidly after a period of 500 years (ca. 2100 BC).

"For an unknown reason, Caral was abandoned rapidly after a period of 500 years (ca. 2100 BC)."

And, elsewhere in the world.

2181-2040 Egypt’s First Intermediate Period. It began with the collapse of the Old Kingdom due to crop failure and low revenues due to pyramid building projects. This seemed to coincide with a period of cooling and drying.

"Caral is indeed hard to accept. It is very old. Still, its dating of 2627 BC is beyond dispute, based as it is on carbondating reed and woven carrying bags that were found in situ."

I agee. Seems solid from all that I've seen.