`...sticking points...why in the hell it took so long...' Carrol
Remember a few things. Absence of evidence is not evidence of absence. Here is something to consider. The bushmen of south eastern Africa or Khoisan (named after their language group) and some of the Ethiopians have the oldest known mtDNA (mitochondria):
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1288201
>From other sources, this L0 and L1 mtDNA is thought to date from
~160-140k/yrs ago. The time frame and the age approximation are the
result of a theory of mutations. The more mutations, the more time has
passed. This is especially true when the mutations take place in the
asexual reproductive cell organelles. Khosian and some Ethiopian
people have the highest degree of variation in their mitochondria or
mtDNA, and are therefore thought to be the origin of all later mtDNA,
which in turn has less and less local variation.
According to my old anthro courses, the bushmen live a nomadic life using few tools. At some point, some of them turned to herding and perhaps had more developed settlements. Their history was to be displaced from more habitable regions by bantu people (also a language group) who developed agriculture. During the earily colonial period the bushman were moved out toward less and less habitable areas. In the past they were thought to use the same limited range of stone tools, mostly digging and scraping implements, i.e. low stone-tech. Other than some large bones and a few of these tools there would be no archeological record of them. On the other hand, they have extensive mythologies and story telling customs, and extensive knowledge of plants/animals and are supposed to be great trackers. i.e. high end use of language. So the conclusion is that low-stone tech doesn't necessarily corollate with low level language skill.
In other words, the assumption behind a late development of language is that high stone-tech indicates high language skill. That seems to be the case. And yet the converse doesn't hold. Low stone-tech does not corollate with low language skill.
There are other problems. The argument for a delayed expression of language from an early capacity seems counter-intuitive and requires some additional assumptions, such as the reason or cause for the delay. Also from other social sciences, it appears that it is impossible to attain full social capability as an adult without language. Since all the ancensors of modern humans were communial, and therefore social animals, it seems initutively more likely they developed their language skills to whatever capacity they had available.
Also there are various arguments that reason, the late paleolithic cultural explosion of artifacts of high quality could reflect social orders and organization of larger and more settled communities with heirarchies of specialization and division of labor, extended trade networks able to pool a greater diversity of natural resources and so forth than were possible in the small mostly nomatic and loosely connected communial groups of earlier periods.
Also I am prejudiced against the idea that we literally bootstraped ourselves from the mists of grunts and cries, and turned ourselves into articulate, fully cultured human beings. I just don't like the idea. It seems far more `natural' that all that grunting and screaming took place long before us.
CG