What “Took Out” the Dinosaurs and the Bees?

18 September 2014

            About 65 million years ago, the dinosaurs went extinct.  They weren't alone.  A large number of bee species went extinct as well.  The question: What took out the dinosaurs and the bees?

          The dinosaurs’ extinction is tricky because 65 million years ago, about 90% of the dinosaurs had already died out.  What was killing them?   A lack of oxygen.

            Remember in the film Jurassic Park.  Dino DNA was discovered in a mosquito sealed in a prehistoric piece of amber.  Well, I don’t know if anyone will ever find good dinosaur DNA, but scientists have found a lot of air bubbles in prehistoric amber.  So many air bubbles that it’s possible to know how much oxygen was in the prehistoric air. 

            When dinosaurs ruled the world, a whopping 35% of the air they breathed was oxygen.  This allowed them to have a relatively inefficient method of breathing.  On the other hand, mammals, like us, had, and have, a very efficient, low-energy respiration system.  But, then, so do insects, like bees.

            65 million years ago, the oxygen in the earth’s air was settling down to its current level of 23%.  The decline from 35% to 23% had spanned millions of years.  And throughout those millions of years, every time the oxygen in the air went down, the number dinosaurs alive on earth went down.

            Then, as the saurian’s teetered on the brink of extinction, something catastrophic happened.  A meteor hit the earth.  Meteors had hit before, but this wasn't your average meteor.  Any relief map of the U.S. will show Arizona’s Meteor Crater.  This easily visible monster of a crater (a bit under a mile wide) was made by a 160 foot-wide piece of space rock when it hit the earth. 

Meteor Crater Arizona

            But the meteor that hit the earth 65 million years ago was a bit bigger – over 40,000 feet wide.  And, when it hit, it was traveling at a speed of about 65,000 mile per hour.  

            This meteor made its mark.  It would have been easier to find its mark if it hadn't landed in the Atlantic Ocean just off the Yucatan Peninsula in Mexico.  The ocean-bottom crater stands as a testament to the size of the meteor and the event. 

Chicxulub Meteor Strike

            The result was dust.  More dust than you could ever imagine.  Blown into the earth’s atmosphere, the dust darkened to sun so much that the earth suffered a night that lasted more than a year. 

            Plants need the sun to survive.  A large chunk of the plant life on earth died.  The animals that fed on that plant life followed quickly.  But, a smaller animal had a smaller appetite and a better chance to live through that long night. 

            The dinos weren't small.  Extinction followed -- quickly.  But a lot of dino’s might have made it through this dusty night in the old days -- those oxygen-rich days when 10 times the dinosaurs roamed the earth and . . . breathing was easy. 

            But what about the bees?  Plants, and their nectar-filled blossoms, are the bees’ “bread and butter.”  And, for plants, the bees are the great pollinators.  Without pollination, there would be no seed for the next – lighter and brighter – season.  Many plant species didn't stand a chance. 

            But how can we know what happened to the bees?  The prehistoric bees left few fossils.  Unlike their prehistoric fellows, the dinosaurs, the bees didn’t hang-out around tar pits and other dangerous locations favorable to fossil formation.  Bees prefer flowers, nectar and sweet tree saps.  Sweet saps?  What happens to sap when it ages a few million years?  It becomes amber.  And, yes, some intact bee remains from prehistoric times have survived.

Prehistoric Carpenter Bee (Xylocopinae)

            Today, there is one “subfamily” of bees, Xylocopinae, with a traceable evolutionary history going back to the age of the dinosaurs -- the Cretaceous Period.  Most of the members of this bee subfamily are carpenter bees.  “Carpenters” are found throughout the modern world.  These bees look a bit like bumblebees.  The name “carpenter” comes from their nesting habits.  These bees build their nests by boring into dead wood – a habit that doesn't always endear them to homeowners.   

            The surviving modern descendants of these prehistoric bees are important to researchers.  We may not have so many bee fossils.  But we do have a sample of the DNA from a prehistoric bee.  We, also, can get a sample of the DNA from its modern descendant.  Comparison and the ancient and modern DNA can tell us a lot about the past.

            The study and comparison showed that the population of at least one group of bees suddenly and seriously declined at the just the time of the meteor strike – 65 million years ago. 

            The dino’s extinction may have more to do with oxygen-poor air than a meteor strike.  But the meteor strike left drastically fewer bees alive on earth.  But, for researchers, this isn’t the end of the story.  With this information, they are hot on the trail of the answers to other questions. 

            We know a lot about the numbers and types of plants that went extinct at the time of the meteor strike.  But, by carefully comparing the timing of the plant losses and bee losses, researchers hope to piece together just what that dusty atmosphere was like and exactly how long it lasted.

            Finally, the story of the prehistoric meteor has recently been pumped full of new life.  Not from a new discovery, but from some name-changing.  A few researchers have decided that the meteor was so big, that it should be reclassified as an asteroid or comet.  This may make little difference to the story of what happened to the dino’s and the bees -- but another day, another headline.

M Grossmann of Hazelwood, Missouri & Belleville, Illinois

18 September 2014

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