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lamdgt
5th May 2011 - 07:57 AM
I had a thought last week about all the speices that have lived on this planet. I think that something besides natural selection might be at work. After many more hours of thought, I came up with this. Every so offten the magnetic poles switch, and for a wile theres no magnetic shild to protect life on the surfice from high energy cosmic rays. i say that its this that pushes eveloution more than anything. On this line of thought, where "population centers" and how much do you think mutations are going to show up in humans after this round?
synthsin75
5th May 2011 - 03:22 PM
That could only effect a punctuated evolution (http://en.wikipedia.org/wiki/Punctuated_equilibrium) rather than a continuous, ongoing process. So basically significant species emergence.

http://en.wikipedia.org/wiki/Geomagnetic_reversal
QUOTE (^+)
The latest one, the Brunhes–Matuyama reversal, occurred 780,000 years ago. Brief disruptions that do not result in reversal are called geomagnetic excursions.


http://en.wikipedia.org/wiki/Geomagnetic_excursion
QUOTE (^+)
One of the first excursions to be studied was the Laschamp event, dated at around 40kyr ago.


http://en.wikipedia.org/wiki/Timeline_of_evolution
These could possibly correspond to:
QUOTE
1 billion years of multicellular life,
600 million years of simple animals,

And:
QUOTE (->
QUOTE
1 billion years of multicellular life,
600 million years of simple animals,

And:
200,000 years since humans started looking like they do today,
25,000 years since Neanderthals died out.


Although probably a very minimal contributor to evolution, as:
QUOTE
Most reversals are estimated to take between 1,000 and 10,000 years.

With geomagnetic excursions (temporary changes without reversal) taking a similar time span. Would be very hard to determine, as punctuated equilibrium still takes a significant ecological time.
QUOTE (->
QUOTE
Most reversals are estimated to take between 1,000 and 10,000 years.

With geomagnetic excursions (temporary changes without reversal) taking a similar time span. Would be very hard to determine, as punctuated equilibrium still takes a significant ecological time.
So by 'rapidly', they mean rapidly by geologist's standards". So with a coarse and incomplete fossil record, "a speciation that took 50,000 years would seem instantaneous", relative to the several million years of a species' existence.
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