I decided to use this activity at the end of our unit on the musculosketal system since we had been working for five weeks putting clay muscles on a skeletal Maniken^TM.  The geology teacher had a set of plaster hominid skulls, so I thought it might be fun to try building faces based on the facial muscles we had been studying. Sort of a new twist on the idea of "form and function". Afterwards, we will compare the student creations to those professional anthropologists are suggesting (see links below)
 

The family of hominid skulls	Building a plaster mandible
It can get interesting

Hey kids . . some links you might want to explore . . . . .

http://www.andreacampbell.com/html/forensic_sculpture.html
http://www.forensicartist.com/facesfrompast.html
forensic reconstruction of Neanderthal man
A look at homo habilis
Handy Man?