Can magnetic pole shifts drive evolution in humans?

[Ynsgfnsv]

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 there's 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?

 

[Ryan_m_b]

You would benefit from learning about evolution rather than just thinking about it.

There are many factors to evolutionary biology beyond natural selection; sexual selection, gene flow, genetic drift etc. Geomagnetic reversals occur over 10s-100s of thousands of years, potentially they would allow higher mutation rates but higher mutation rates would not necessarily lead to increased speciation or adaptation, the drivers of those two things are the processes I have listed above plus natural selection. I am unaware of any peer-reviewed study that has compared the rates of evolution under periods of geomagnetic reversal, rather than stating

i say that its this that pushes eveloution more than anything

You should try to find evidence from peer-reviewed literature to back up your claims. I don't know what you mean by "population centers" nor "this round"

 

[Ophiolite]

Every so offten the magnetic poles switch, and for a wile there's no magnetic shild to protect life on the surfice from high energy cosmic rays.

This is misleading. During a reversal the magnetic field weakens and goes through rapid variations in geometry. (The current South Atlantic anomaly may be an expression of this process.) The field never goes away completely. Most of the planet, most of the time is 'reasonably well' protected.

While the bulk of the planet is shielded by the current arrangement, the poles are relatively exposed. I don't know of any studies that show that penguins and polar bears have higher mutation rates than guillemots or grizzlies. (Equally I don't know of any studies that show they don't.)

Geomagnetic reversals occur over 10s-100s of thousands of years

This is also misleading. The reversals certainly do not take thousands of years and probably not tens of thousands. Around a thousand or a few thousand years is the general consensus, although http://www.es.ucsc.edu/~rcoe/coepubs/coe63.pdf" suggest much shorter time intervals may be possible.

i say that its this that pushes eveloution more than anything.

As Ryan suggests go look for studies that would back this up. I have seen, but can no longer locate, a study that considered the last two or three hundred million years of reversals and looked for a correlation with extinction rates. None was found. Since many of the major evolutionary changes have been contingent on extinction events, this suggests a relationship such as you propose is unlikely.

 

[Ryan_m_b]

This is also misleading. The reversals certainly do not take thousands of years and probably not tens of thousands. Around a thousand or a few thousand years is the general consensus, although http://www.es.ucsc.edu/~rcoe/coepubs/coe63.pdf" suggest much shorter time intervals may be possible.

If you've got links studies showing that 10-100s of thousands of years is too long then I'm not misleading, I'm wrong

 

[mishrashubham]

If you've got links studies showing that 10-100s of thousands of years is too long then I'm not misleading, I'm wrong

Wikipedia says (with the support from a reference)

Most estimates for the duration of a polarity transition are between 1,000 and 10,000 years.

As Ophiolite said, even smaller durations have been proposed

However, geologist Scott Bogue of Occidental College and Jonathan Glen of the US Geological Survey, sampling lava flows in Battle Mountain, Nevada, found evidence for a reversal that took only four years.

Wikipedia also says

There is no uncontested evidence that a magnetic field reversal has ever caused any biological extinctions. A possible explanation is that the solar wind may induce a sufficient magnetic field in the Earth's ionosphere to shield the surface from energetic particles even in the absence of the Earth's normal magnetic field.
Another possible explanation is that magnetic field actually does not vanish completely, with many poles forming chaotically in different places during reversal, until it stabilizes again.

In addition, does anyone have access to http://geology.geoscienceworld.org/cgi/content/abstract/8/12/578?
I would really like to go through it.

@OP
As Ryan said, reading about the subject would be very helpful, However thinking and analyzing is also equally important (although this comes after the reading).
There are many mechanisms through which evolution occurs (refer to Ryan's links). In fact your case can be considered a population bottleneck (if the hypothesis about mass extinction due to exposure to cosmic radiation is right); where there is a sudden decrease in population leading to an increase in genetic drift and decrease in variation.

 

[DavidMcC]

Magnetic pole reversals, apart from causing increased surface radiation levels, would be bad news for any species that migrates long distances using a magnetic compass, because it would entail a very weak and randomly varying field during the reversal. This would also cause problems for many bat species, which use the Earth's field to orient their daily foraging trips. When the field is too weak, they would have to use other senses, and this could be part of the reason that nearly all bats have quite good eyesight, IMO, although there are other advantages in having a high resolution sense, even if it only works at a certain light level. Very few modern bat species are completely blind, and magnetic pole reversals are probably part of the reason, since they occur just about frequently enough, at about one every 800KY (I think).

 

[Ryan_m_b]

Magnetic pole reversals, apart from causing increased surface radiation levels, would be bad news for any species that migrates long distances using a magnetic compass, because it would entail a very weak and randomly varying field during the reversal. This would also cause problems for many bat species, which use the Earth's field to orient their daily foraging trips. When the field is too weak, they would have to use other senses, and this could be part of the reason that nearly all bats have quite good eyesight, IMO, although there are other advantages in having a high resolution sense, even if it only works at a certain light level. Very few modern bat species are completely blind, and magnetic pole reversals are probably part of the reason, since they occur just about frequently enough, at about one every 800KY (I think).

I don't think the field would ever be week enough not to be detected by magnetosensing animals. I did have a reference for that a few days ago but I can't find it atm

 

[DavidMcC]

Then I would be grateful if you could find it, Ryan.
Thanks.

 

[Ryan_m_b]

It was on this forum somewhere on a previous magnetic reversal thread. A quick google gives this link http://geology.about.com/cs/basics_deep/f/faq3magreversal.htm that has some information

 

[DavidMcC]

Thanks, Ryan. However, I am not entirely convinced by "A compass will always point somewhere.". There would come a point when a biological compass would be unreliable, I would have thought, due to a very weak field, forcing animals to use other cues. Long distance migrations would suffer from the further complication from the break-up of the dipole field into a patchy field distribution befgore it disappeared altogether, perhaps with more than one apparent "magnetic pole" due to "non-dipole" fields, again forcing animals to rely on other cues to avoid getting lost.
Obviously, populations do avoid extinction, but it is not yet clear how, in spite of "A compass will always point somewhere.".

 

[Evo]

Thanks, Ryan. However, I am not entirely convinced by "A compass will always point somewhere.". There would come a point when a biological compass would be unreliable, I would have thought, due to a very weak field, forcing animals to use other cues. Long distance migrations would suffer from the further complication from the break-up of the dipole field into a patchy field distribution befgore it disappeared altogether, perhaps with more than one apparent "magnetic pole" due to "non-dipole" fields, again forcing animals to rely on other cues to avoid getting lost.
Obviously, populations do avoid extinction, but it is not yet clear how, in spite of "A compass will always point somewhere.".

Here you go.

History seems to back this up. There is no firm evidence that the many magnetic field reversals that have taken place throughout our planet's history (see When Compasses Point South) have coincided with or triggered extinctions. Reversals take hundreds if not thousands of years to complete, and because for anyone type of animal that represents hundreds or thousands of generations, species have time to accommodate to the change. Moreover, Kirschvink notes that even if the main dipole field were to collapse—an event that can last for up to 10,000 years during a reversal—residual fields 5 or 10 percent as strong as the main field would remain on the surface, and animals would be able to use those quite well for migration.

http://www.pbs.org/wgbh/nova/magnetic/animals.html

 

[DavidMcC]

Thanks for the link.
As the article says, it is not known for sure exactly how animals that migrate using magnetic sensing survive a pole reversal, and one possibility is that:
"... magnetic sensitivity is just a backup system of navigation, or one component of a more sophisticated way to stay on course."
An experiment with bats done about 5 years ago suggested the possibility that bats have at least some difficulty in reading their "batnav" compass. The resaerchers used a bat colony that roosted in a barn to test the effect of an artificial pole reversal - they applied a reverse field to the barn and waited to see which direction the bats would fly out in the evening. It turned out that they flew in the "wrong" direction, as expected if they relied on their field sensing. However, once they were away from the barn, they nearly all carried on in the "wrong" direction, with a few individuals "peeling off" from the rest, having apparently realized their mistake. Presumably, the majority were simply following the leader, without bothering to check for themselves if they were going the right way.
The conclusion I draw from this is that bats find it difficult to read their magnetic compasses. If that is the case, they might well have to fall back on other cues if the Earth's magnetic field gets much weaker than it is now.
Unfortunately, I do not have the reference to that work, which was posted on the original "richarddawkins.net" evolution forum, now permanently off line, alas (replaced by a new site, which did not retain all the old threads).

 

[ViewsofMars]

I'm rushed for time but thought the following three articles might help this discussion.

1. Princeton paleomagnetists put controversy to rest
http://www.princeton.edu/main/news/archive/S25/44/95K79/index.xml?section=newsreleases

2. Nature Geoscience 2, 713 - 717 (2009) - No asymmetry in geomagnetic reversals
recorded by 1.1-billion-year-old Keweenawan basalts. Please note from the on-line
document the following: Corrected online: 13 April 2010 | doi:10.1038/ngeo622 and
'a Corrigendum (May 2010) associated with this Letter'.
http://www.nature.com/ngeo/journal/v2/n10/full/ngeo622.html

 

[Evo]

Thanks for the link.
As the article says, it is not known for sure exactly how animals that migrate using magnetic sensing survive a pole reversal, and one possibility is that:
"... magnetic sensitivity is just a backup system of navigation, or one component of a more sophisticated way to stay on course."
An experiment with bats done about 5 years ago suggested the possibility that bats have at least some difficulty in reading their "batnav" compass. The resaerchers used a bat colony that roosted in a barn to test the effect of an artificial pole reversal - they applied a reverse field to the barn and waited to see which direction the bats would fly out in the evening. It turned out that they flew in the "wrong" direction, as expected if they relied on their field sensing. However, once they were away from the barn, they nearly all carried on in the "wrong" direction, with a few individuals "peeling off" from the rest, having apparently realized their mistake. Presumably, the majority were simply following the leader, without bothering to check for themselves if they were going the right way.
The conclusion I draw from this is that bats find it difficult to read their magnetic compasses. If that is the case, they might well have to fall back on other cues if the Earth's magnetic field gets much weaker than it is now.
Unfortunately, I do not have the reference to that work, which was posted on the original "richarddawkins.net" evolution forum, now permanently off line, alas (replaced by a new site, which did not retain all the old threads).

Please follow the guidelines and post link to the articles to which you are referring.

 

[DavidMcC]

As I said, Evo, "Unfortunately, I do not have the reference to that work, which was posted on the original "richarddawkins.net" evolution forum, now permanently off line, alas (replaced by a new site, which did not retain all the old threads)."
In other words, I couldn't post a link.

 

[DavidMcC]

OK, I got lucky, and found the exact paper with a search engine:
http://www.batcon.org/index.php/media-and-info/bats-archives.html?task=viewArticle&magArticleID=992"

 

[DavidMcC]

Thanks, ViewsofMars. I especially liked the title, "In GAD we trust"!
Does that mean that magnetic field reversals are dependent on plate tectonics in the polar regions at the time of the reversal? If so, it would be even harder to predict the response of any given species to a reversal, and it's hard enough as it is!

 

[DavidMcC]

... If the observed irregularities were entirely an artifact of plate movement, then the actual field remained dipole, and therefore went to zero everywhere at some point in time, right?

 

[ViewsofMars]

The conclusion I draw from this is that bats find it difficult to read their magnetic compasses. If that is the case, they might well have to fall back on other cues if the Earth's magnetic field gets much weaker than it is now.
Unfortunately, I do not have the reference to that work, which was posted on the original "richarddawkins.net" evolution forum, now permanently off line, alas (replaced by a new site, which did not retain all the old threads).

and

OK, I got lucky, and found the exact paper with a search engine:
http://www.batcon.org/index.php/media-and-info/bats-archives.html?task=viewArticle&magArticleID=992"

I need a reputable peer-reviewed paper that states what you have implied when you stated, "if the Earth's magnetic field gets much weaker than it is now." Dave, the article from your link is from VOLUME 25, NO. 2 Summer 2007. It does state in that article, “More research is needed to better understand the details of how bats and many other wide-ranging animals find their way across landscapes near and far.”

My contribution on the previous page stands since it is from a peer-reviewed journal. You may like to read it again. Getting back to bats, the California Academy of Sciences had an article from March 30, 2010 regarding “Extreme Bats”. You will have to go online to review the scientific papers therein:

[snip]
Two recent papers in the Proceedings of the National Academy of Sciences reveal even more fascinating, extreme bat behavior.

Scientists from Brown University and Japan report that echolocating bats traveling in large groups minimize sound wave interference by tweaking the frequencies of the sounds they emit — their broadcasts — to detect and maneuver around obstacles. The scientists also found that bats make mental templates of each broadcast and the echo it creates, to differentiate one broadcast/echo set from another. According to James Simmons of Brown, “They’ve evolved this, so they can fly in clutter. Otherwise, they’d bump into trees and branches.”

Meanwhile, in Germany, researchers from the Max Planck Institute for Ornithology found that the greater mouse-eared bat uses an internal compass and the Earth’s magnetic field to navigate in the dark. The fact that the greater mouse-eared bat does not use echolocation, even when hunting for food, makes this finding even more surprising.

The scientists don’t know how the bats detect the magnetic field, but according to New Scientist, “By exposing bats to a short pulse of skewed magnetic field during and after sunset,” they found that exposure “during sunset confused the bats, causing them to fly in the wrong direction, while experiencing it after the sun had set had no effect. This is strong evidence that the bats rely on the magnetic field while flying at night, after calibrating it by noting where the sun has set.”
[snip]
http://www.calacademy.org/sciencetoday/extreme-bats/

Bye the way, California Academy of Sciences has an exceptional website. I encourage people to explore this great resource.

ErekAlert is affliated with the American Association for the Advancement of Science. It had an article on May 9, 2011 entitled 'Bats lend an ear to sonar engineering" that I thought was fasinating:

[snip]

Bats are one of a few animal groups that demonstrate biosonar—the ability to generate and emit ultrasonic pulses and gauge the reflections to obtain detailed information on their surroundings.

Bats use biosonar as a way of navigating and hunting for food, however researchers have seen its potential to inspire new ways of engineering where manipulating outgoing or incoming waves with structures is a principal component.

Lead author Professor Rolf Müller, of Virginia Tech, said: "Using physical shapes to manipulate an outgoing or a received wave has application in many areas of engineering. Besides the obvious analogues of SONAR and RADAR, such principles could also find application in biomedical ultrasound, non-destructive testing, wireless communications, and sensory systems for autonomous robots and nodes in sensor networks."

The ear of a bat plays a crucial role in the overall sensing system by acting as a baffle to diffract the incoming waves therefore determining the ear's pattern of sensitivity to direction and frequency.

[snip]

The researchers also demonstrated how this variability can affect the properties of beamforming—the process by which the incoming signal is diffracted by the shape of the pinna to create a "beampattern" through which the bat sees it environment.

The variability occurs as a result of the evolution of bats whose habitats range from environments with virtually no structures, to those with simple structures (calm water surfaces), to habitats with very complicated structures (dense forests).

The researchers found, for example, that a group of bats that hunts for prey in dense vegetation with trains of long, closely-spaced objects are separated from other bats by the widths of their pinna openings, demonstrating how biodiversity can provide a useful insight into how a general principal can be customised to fit different needs.

[snip]

http://www.eurekalert.org/pub_releases/2011-05/iop-bla050511.php

 

[DavidMcC]

ViewsofMars: 'I need a reputable peer-reviewed paper that states what you have implied when you stated, "if the Earth's magnetic field gets much weaker than it is now."'

Look, Views, I was only trying to show that bats COULD be in a difficult situation during a magnetic pole reversal w/r to their use of magnetic compasses. I'm afraid I haven't got time to pursue everything myself to your satisfaction.

 

[Phrak]

This is misleading. During a reversal the magnetic field weakens and goes through rapid variations in geometry. (The current South Atlantic anomaly may be an expression of this process.) The field never goes away completely. Most of the planet, most of the time is 'reasonably well' protected.

If I may back up a few days, what does 'expression' mean?

 

[DavidMcC]

Views, I now realize that the paper you ask for is the one you linked before, entitled:
"No asymmetry in geomagnetic reversals recorded by 1.1-billion-year-old Keweenawan basalts"
I merely argued that a symmetrical axial diploe moment has to go to zero if it is to reverse and remain axial and symmetric. If there is a quadrupole moment that maintains a finite field and that doesn't reverse, then that would break the symmetry.

 

[DavidMcC]

If I may back up a few days, what does 'expression' mean?

Phrak, I think it is clear that in this case "expression" means "example".

 

[Phrak]

OK. So according to your interprestion, he thinks the South Atlantic anomaly is an example of a rapid variation that leads to a pole reversal. So the South Atlantic anomaly will lead to a pole reversal. I don't think he is proposing this.

 

[Ophiolite]

Phrak, I state that "the South Atlantic Anomaly may be an expression of this". There is certainly speculation that this could be the case. Simulations of variations in the magnetic field show the emergence of anomalies like the SAA. (Thank you to David for correctly clarifying that expression = example in this instance. Since we are talking about a dynamic process the word expression seemed better than example.)

However, we do not have enough extended detailed history of field variations to know whether the SAA is an excursion that is part of a larger reversal mechanism, or if it is simply a 'random' fluctuation in the field. So we might be witnessing the start of a reversal, or we may have to wait another 10,000 or a 100,000 years before one occurs.


On the subject of animal navigation it is my impression that many of them use multiple techniques. Consequently a polar reversal might inconvenience them rather than prove fatal.