Kennita
Continental shifts may have led to evolution explosion
July 25, 1997
Web posted at: 10:12 p.m. EDT (0212 GMT)
LOS ANGELES (CNN) -- One-half billion years ago, for reasons scientists have
never clearly understood, there was an unprecedented burst of evolutionary
activity, greater than any before or since.
Now, researchers at the California Institute of Technology and the Oak
Ridge National Laboratory in Tennessee have a theory as to why
that happened -- one which even they admit is radical.
The theory, reported in Friday's issue of Science, is called "true polar
wander." These researchers say there was a massive shift and realignment
of the Earth's continents over a 15-million-year period -- at a pace about
10 times as swift as the shift of continents under way today.
They theorize it could have been caused by polar land masses that made the
spinning Earth too top- and bottom-heavy.
And when the shift was over, land that used to be at the poles was at the
Equator and vice versa. North America shifted north from the Southern
Hemisphere.
If this shift took place, cold continents would have thawed and tropical
continents would have cooled. Similar upheavals would have taken place in
the oceans. And the ensuing environmental changes caused by all of this
created the chaotic conditions needed for rapid evolution.
"Something like 40 different major groups of animals make their first
appearance during this time," says Joe Kirschvink, a professor of geology
at Cal Tech. "It's an incredible bloom."
This evolutionary period is known as the "Cambrian explosion" or "big bang."
It was during this time that many multi-celled organisms emerged whose
descendants, including human beings, populate the Earth today.
However, this new theory is not universally accepted, with some scientists
saying the evidence supporting it is scanty. But researchers at Cal Tech
believe they can test the theory to see if, indeed, "true polar wander"
may be responsible for life as we know it.
Kennita Watson | The bond that links your true family is not one of blood,
kwatson@netcom.com| but of respect and joy in each other's life. Rarely do
| members of the same family grow up under the same roof.
| -- Richard Bach, _Illusions_