Evolution brings a sense of humility like nothing else can. Ladies and gentlemen, may I introduce you to our ancestors? Featured on the first slide is “Kimberella,” probably the oldest of the “protostome” fossils, dating 255 million years ago – from before the pre-Cambrian explosion.
“Aha,” you might be thinking. “That doesn’t look like even the worst of my family members, so how can this be my distant relative?” But if you can read this, you do indeed share some of the same genetic sequences with Kimberella, because as a protostome, we have in common a bunch of “master genes” that extend that far back in time.
In fact, they trace their origins all the way to a hypothetical genus called the “Urbilateria,” which certainly did not look like the second image. (I just put something bug-like and squiggly there to set the mood.) Because of the recently developed science of Evo Devo, scientists have been able to trace our family trees back in time to find common genetic sequences which act as tool kits, giving a sort of modular construction to physical forms that seem totally dissimilar.
I shall introduce a few to you. First, we have a bunch of “Hox” genes. These have to do with the symmetrical arrangement of the body (we are bilateral, and do not radiate like starfish). And then there is “Pax-6,” which deals with eyesight, “tinman,” referring to the circulatory system, and “Distal-less,” which is all about potential limbs.
These master tool kits have allowed for the enormous range of diversity in living animals — with the specifics in each family tree building off of these foundations.
Source(s): _Endless Forms Most Beautiful: the New Science of Evo Devo_, by Sean Carroll, Norton, 2005. Kimberella image Wikipedia. Crazy bug is author’s rendition of Mike Francina’s original “Nun of the Church of Metamorphosis”.
