The oldest spearhead to date

[Newbow]

Patrick:  The questions you pose are exactly the type that should be addressed to any new ideas that have to be inferred from evidence rather than from direct observation.  Questioning and testing proposed ideas is key to science, but to answer your question, yes, I buy the conclusions of the article.  I do so with the caveat that it is a statement of current thought and not the end-all final word.  If asked I would tell someone that "this is what they are saying about that today and this is why they are saying it".  If I am aware of a minority view I would mention it as well.  The reason that I "buy" the authors' conclusions is the huge amount of research that went before them.  The vast majority of the references cited in the paper refer to published work on exactly the same subject.  These previous papers address most, if not all of your concerns (An example from the Journal of Archaeological Science: http://www.sciencedirect.com/science/article/pii/S030544031100080X).  The majority of the cited references have links the original paper, though in some cases you'll only get to see the abstract unless you want to pay for the entire thing.  Given some of the various titles, I'm taking at as an article of faith (I have only glanced at some of them) that those papers did sufficient impact testing to reasonably rule out impact damage in the form you suggest could be confounding.  The authors of the current paper also assumed the findings of the other papers to be reasonable and conducted their measurements based on those other papers, using only those points that exhibited damage that might be expected of impact, their purpose being to support mathematically the hypothesis (that hafted projectiles were probably in use much earlier than previously believed) of some of the other authors.  Again, as an article of faith, I have to accept that the microfracture features they tested for are truly diagnostic.  If they are not, someone will publish a paper challenging their findings, but I am not qualified to do so.  I might find that information if I were sufficiently motivated to read each of the 46 papers that these authors supplied links to, but I'm not.  Often, knowing the entire background of an investigation will allay reservations about the conclusions reached.  Not so often, but not never, knowing the background information will raise concerns rather than allay them.  I can't knowledgeably answer the questions you've posed.  If you are uncomfortable with my "article of faith" position, I suggest you contact the paper's authors at: yonatan.chemere@uct.ac.za.  That is the contact email for three of the authors at the University of Cape Town, South Africa.  Tell them you are a knapper and also do a column for PA and have questions and I'll bet they'll either answer directly or refer you to the paper(s) that address your concerns.

[JackCrafty]

Newbow, thank you very much for your response.  Honestly, I didn't know what to expect.  I am pleasantly surprised and very grateful.

I purchased the article.  The 10 pages were worth the money.  It appears that microfracture features (seen only with a microscope/magnification), that indicate the speed of fractures, are present on very fine grained materials and obsidian.  The article focuses on the idea that "dynamic" (extremely high speed) fractures are caused by projectiles traveling at high speeds.  That makes sense but, like you said, further testing is needed.  If another method of producing these "high speed cracks" can be found, it could ruin everything.  Finding these features on pre-human or non-human altered objects could also prove disastrous.  Time will tell.

In my opinion, the greatest potential benefit of this research is in the manufacturing/reproduction of the artifacts.  Knowing the speed of the fracturing and the corresponding knapping method/material that produced that speed could settle questions about manufacturing processes once and for all.  Very exciting stuff!

I'm sure someone else has thought of this too.  I will write to the authors and find out.... unless you already know the answer and are willing to share a link to another paper? 

[Newbow]

"In my opinion, the greatest potential benefit of this research is in the manufacturing/reproduction of the artifacts.  Knowing the speed of the fracturing and the corresponding knapping method/material that produced that speed could settle questions about manufacturing processes once and for all."

That's a direction for this line of inquiry I hadn't considered.  As you suggest, if demonstrated practical, that information could answer a whole lot of questions near and dear to the hearts of flint knappers as well as the greater archeological community.  I'm unaware of any research paper that deals with the "how" of tool manufacture in that way but on the face of it, it should be possible.  By all means, write and see what they can tell us!

[JackCrafty]

I will do that.   

[JackCrafty]

Since I am now on the Science Direct mailing list, I received an email that shows articles that cite the article I purchased:

Wallner lines in a nanocrystalline Ni-23% Fe alloy
Scripta Materialia, Volume 67, Issue 11, 2012, 907-910
Jiang F., Vecchio K.S.

Thinking a bow-and-arrow set: Cognitive implications of middle stone age bow and stone-tipped arrow technology
Cambridge Archaeological Journal, Volume 22, Issue 2, 2012, 237-264
Lombard M., Haidle M.N.

Assessing the macrofracture method for identifying Stone Age hunting weaponry
Journal of Archaeological Science, Volume 38, Issue 11, 2011, 2882-2888
Pargeter J.

Rock type variability and impact fracture formation: Working towards a more robust macrofracture method
Journal of Archaeological Science, Volume 40, Issue 11, 2013, 4056-4065
Pargeter J.

European Neanderthal stone hunting weapons reveal complex behaviour long before the appearance of modern humans
Journal of Archaeological Science, Volume 39, Issue 7, 2012, 2304-2311
Lazuén T.

Identifying design and reduction effects on lithic projectile point shapes
Journal of Archaeological Science, Volume 41, 2014, 297-307
de Azevedo S., Charlin J., González-José R.

Projectiles and the abuse of the use-wear method in a search for impact
Journal of Archaeological Science , , 2013,
Veerle Rots, Hugues Plisson

Chronological and behavioral contexts of the earliest Middle Stone Age in the Gademotta Formation, Main Ethiopian Rift
Quaternary International , , 2013,
Yonatan Sahle, Leah E. Morgan, David R. Braun, Balemwal Atnafu, W. Karl Hutchings

Projectile impact fractures and launching mechanisms: results of a controlled ballistic experiment using replica Levallois points
Journal of Archaeological Science , , 2013,
Radu Iovita, Holger Schönekeß, Sabine Gaudzinski-Windheuser, Frank Jäger

Dynamic fracturing: field and experimental observations
Journal of Structural Geology , Volume 23, Issue 8, 2001, 1223 1239
Amir Sagy, Ze'ev Reches, Itzhak Roman

Fracture markings from flake splitting
Journal of Archaeological Science , Volume 37, Issue 8, 2010, 2061 2065
Are Tsirk