Adventures in Geology – Part 3

Why and how did humans come to be here?  Why is a question for philosophers, but how is easier to answer.  We know that the dinosaurs had a really bad day 66 million years ago, and that our fellow mammals rose to be the dominant life forms as a result.  The Nova episode:  Rise of the Mammals examines how this domination began, and it’s one of my favorite episodes to date.

One of the big problems facing scientist studying this is that fossil mammals from this time period have been extremely rare.  Rare until Tyler Lyson & Ian Miller, of the Denver Museum of Nature & Science, starting digging at Corral Bluffs, Colorado.  Previously fossil mammal finds from that time had been teeth no bigger than the head of a pin, but at the 400 feet of exposed rock rising above the Cretaceous–Paleogene (K–Pg) boundary that is Corral Bluffs something wonderful was found.  The first mammal find at that site was made by museum volunteer, Sharon Milito, and it sat in a drawer for years until Tyler Lyson found it again.  He also found that this fossil, of a mammal’s pallet, was preserved in a special type of rock known as a concretion.  Since concretions can form around bone protecting it for fossilization, the scientists knew what kind of rock to look for.  And find them they did!

They not only found dozens of mammal fossils, but they also found plant and reptile fossils as well.  They had a lot of help freeing these fossils from their stony matrices, and with identifying them.  They also kept going back to Corral Bluffs.  Geologists joined them there, and they were able to date two different magnetic “flips” recorded in rocks at two different stratigraphic layers.  Because of that we now know that Corral Bluffs records the first million years after the dinosaur extinction, and it includes the first mammals to specialize into a niche once held by the dinosaurs.  One of these early mammals, “Loxolophus, scavenged for food…within the first 300,000 years after the [fifth] extinction.”  Scientist think that it looked somewhat like the raccoon that you see below.

Image by Nature-Pix from Pixabay

We live in difficult times and we may be in a sixth mass extinction right now, but life will prevail again.  I hope we can use our intelligence rather than our fears as we continue our journey as a species.  My next post will be about a book that I’m listening to called the “Goldilocks Planet.”