>> I presume an endocast is a cast of the inside of the skull (which leaves
>> the question: how do the extract the cast after making it? Maybe they use a
>> layer of flexible material which when it solidifies can be withdrawn
>> through an opening? Surely they don't break the skull. Or maybe they use
>> partial skulls?)
Yes, it is a cast of the inside of the skull, and, as Glenn said,
mucking around with latex or something similar is involved, but I don't
know much about the details. (Last night I tried to find some info I
though I had read recently, with no luck. I'll let you know if I find
it.)
Doing a complete intact skull would be tricky, given that you only have
the foramen magnum (about 1 inch diameter) to work through. However most
hominid fossils are both less complete and already broken. The base of
the skull in particular is usually missing, even on relatively complete
specimens, so that would give better access to the interior.
>> My (main) questions are: What do endocasts show? Do they actually show the
>> shape of the brain? Down to what level of detail? Or do they simply show
>> the shape of the skull which contained the brain, in which case some
>> details about brain structure are lost. If they show the shape of the
>> brain, how can this be? I thought soft parts generaly just decayed,
>> leaving only hard parts like bones to fossilize.
They often show major blood vessels, and bumps on the brain such as
Broca's area. Soft parts are not preserved, but it seems that they are
capable of leaving an imprint on the inside of the skull. However I've
read that this sort of stuff is not always preserved, so you can't
really use endocasts as negative evidence, to prove that something isn't
there; it's more useful for proving the presence of something rather
than its absence. Interpreting endocasts is pretty tricky stuff.
-- Jim Foley Symbios Logic, Fort Collins, COJim.Foley@symbios.com (303) 223-5100 x9765 I've got a plan so cunning you could put a tail on it and call it a weasel. -- Edmund Blackadder