By definition, pre-speech thought preceded speakable thought, so the idea that there was a relatively isolated part of the brain that developed speech but we couldn't understand it is pants-on-head retarded.
Actual evidence against it is how anosognosia, causable by ECT, makes a personal unable to recognize deficits in activity that normally come from non-verbalized brain activity. A theory that described self-awareness as weaker (since it had to develop after the initial brain stuff) is legitimate. Ironically Autism could've been a more normal state of people back in the day, since they lack self-awareness. It'd be interesting if originally, men lacked self-awareness because it developed in women first, or was just disabled. Men would've had an advantage of being massive risk takers and able to do the obsessive shit like tool-refining and studying crap for decades for no discernible reason, before we had conscious planning of it. The Y chromosome has gotten smaller over time, so a mechanism which prevented men from having the self-awareness deficit could've been lost. It would have reduced gender differences in cognition and mental models, and allowed men to participate in social activities better, and lead to the non-alpha social structure. Autism could be a throwback to genetic activity which may have been "moved" off the Y chromosome to other DNA and inactivated (which happens a lot in species which have a sexual-determination chromosome). Men have less brain assymetry, and women are normally considered better in left-hemispheric activity, so this theory could hold some weight.