Abstract thought isn't an all or nothing concept. My bats can plan, but
their plans are very simple. H. sapiens in the strict sense seems to be
able to make complicated plans, while the evidence for planning in H.
neanderthalensis suggests less complexity. That would probably correlate
with less working memory capacity in the prefrontal cortex.
On the other hand, the difference between the two might have been in
artistic creativity. I don't know if any imaging work has been done on
artists, so I'm cross-posting this to bionet.neuroscience.
--
Dr. Harry Erwin, harry at dherwin.org, http://world.std.com/~herwin