Bill Hylander and the Grayson High School EcoClub

On April 5th, Bill Hylander (, delighted an inquisitive group of high school students with a careful description of primate history.  Bill’s focus was placed upon the evolution of jaw bones and cranial structure, (his expertise), and he brought with him several models of skulls.  His approach was sensitive to the fossil evidence, and how we know what we know.
Understanding the biology of us, and all the other living things with which we share a genetic past, was emphasized by his discussion of the historic splitting where and when.  Divergence was best demonstrated by his discussion on chimpanzees, with whom we 'parted' long ago.  Humans are not in direct lineage with chimpanzees, though chimps and humans do share a common ancestor.  

The tree of species evolution is full of branches and offshoots, most of which have been dead ends.  Species living today can be traced all the way back to the first life forms on the planet. Every living individual has an ancestor that is so closely related that it is indistinguishable from its next nearest ancestor and successor.  But...when you look at a really long time line, like tens of thousands of generations, there are definite differences.  Bill shared an illustrative idea of stacked pictures with a snap shot of any of us on the top and our great (to the millionth) grandmother at the bottom.  Every picture looks like the others on each side, but carried to this extreme, the differences are huge and the bottom picture is likely a fish.
Bill pointed out that the life forms existing today share common ancestors, but are not descendants of other forms also existing today.  We and chimps are on the tips of our respective branches and have a common ancestor back at the last fork, for example, but we did not evolve from chimps.  We are each ends of a different branch of the evolutionary tree.

An important aspect of Bill’s presentation was the hands-on experience with the skull models.  Many students had good questions, which Bill entertained for another half hour.  

Many many thanks to Bill for making time for BRDC and the ECO Club!

William Roberts

Scott Jackson-Ricketts