Past perfect or present perfect

[manhhiep2509]

This is an example:

A scientist has found that an artifact, buried since approximately 1500 B.C., is encrusted with silk, a fabric previously thought to have been invented 1,000 years later.

I am not sure whether "have been invented" is past perfect or present perfect.
Sometimes I see structures such as "having done something" but I did not find any clue to determine their tense.

Please explain the example and give advice to find tense of such phrases.

Thank you.

[RonPurewal]

Please read the forum rules: read-before-you-post-general-verbal-folder-guidelines-t2718.html

You can't post problems in this folder without giving the original source of the problem -- i.e., the company or author that first produced the problem (= not a forum or other secondhand source).
If you don't know the original source, then i'm sorry, but you can't post the problem here.

If the original problem is accompanied by answer choices, then you must also give all of the original answer choices.

If these things are not done, then we can't answer the question.
Thanks.

[manhhiep2509]

I modified the question from a question in Kaplan premier 2013. Since it is not an original question, I cannot provide any another choice.

[RonPurewal]

Ok. Well, Kaplan itself is a banned source, but, if you modified the question, then fine.

In terms of the "to ___" construction, the only way to make that construction refer to something previous to the timeframe of the sentence is "to have ___ed".

e.g.,
Joe claims to live in Antarctica. --> He claims to live there right now.
Joe claims to have lived in Antarctica. --> He clams that he has lived there at some point in the past.

The state offered aid to anyone believed to be affected by the hurricane. --> A hurricane happened. Pretty much immediately afterward -- soon enough that the two events can reasonably be grouped within the same timeframe -- the state offered relief to the people affected.
In 1985, the state offered aid to anyone believed to have been affected by a hurricane. --> In 1985, the state offered help to anyone who had ever been affected by a hurricane at any point before 1985.

Etc.