Let's approach this tactically. Unlock the convoluted sentence by referring the following examples.

Simple: I purchased vegetables from a Japanese shop. <<--- I am confident that the shop was of a Japanese.
Note that "stunning evidence ..." is not modifying "hunting ground". What is actually the stunning evidence? It is that "400,000-year old wooden spears have been unearthed from an ancient hunting ground".
The entire clause is the stunning evidence.

Complex: I purchased vegetables from what appears to be a Japanese shop. <<--- Here, I am trying to figure out that it appears to be a Japanese shop.

Option A - Incorrect
-Not clear as to whether the spears or the hunting ground serve as evidence.
We could also pinpoint the actual claim. Thus, this makes the option incorrect.

Option B - Incorrect
"What it appears" is awkward (same goes for A, as well). Implies that the hunting ground itself is the stunning evidence. So here, this option is incorrect modifier, "appears was" is imprecise incorrect.

Option C - Incorrect
"Appear was an ancient... hunting ground" AND "is stunning"... Clearly not parallel and the sentence doesn't show a clear meaning. This option is however incorrect.

Option D - Correct
This option is in similar lines with additional absolute phrase modifier stunning evidence in the end.
"stunning evidence..." in this option is an absolute phrase. An absolute phrase is a group of words that modifies an independent clause as a whole. This sentence actually uses absolute modifier construct (evidence that human ancestors systematically hunted big game much earlier than believed).

Option E - Incorrect
"stunning of human is wrong..." simply because the evidence shows something so we need a restrictive pronoun "that". Using "OF" distort the meaning.