April 5, 2010

Michael Jennions
Australian National University in Canberra
Canberra City ACT 2601

(02) 6125 5111

Dear Michael Jennions:
I have read with interest the brief review (Lend a Helping Claw NATURE vol. 464 no. 7288 March 25, 2010 page 469) of your article (Am. Nat. doi:10.1986/651588 (2030)) about scuffles between hermit crabs. 

You observed that among fiddler crabs when an intruder comes to where there are two neighbors and picks a fight with one of them, the other neighbor may come to the assistance of the one being attacked.

You attribute this to the notion that the neighbor is a known quantity while the intruder may ultimately become a bigger threat.  And so of course it may be.

But there is another possibility you might want to consider.  It can be shown with an enormous amount of evidence that fertility is related to gene pool size.  I have posted evidence along with thoughts and letters on nobabies.net and suggest the March 25, 2010 entry as the easiest place to start. 

It would seem that on average the intruder is likely to be less closely related to the crab deciding whether to intervene than the neighbor is.  In that case, the crab is rallying to defend a cousin rather than to defend a neighbor.  And he is risking life and limb to keep the gene pool from enlarging; from a selective standpoint that would be a good investment to make.  Hardly anything short of extermination trumps fertility. 

I cannot tell from the brief review whether you have taken kinship into account.  If so, let me know and I’ll try to find your original article.  Otherwise, some day you might want to try it out.  Arrange for the neighbors to be unrelated and for the intruder to attack the resident which is not kin.  See if the other resident rallies to his neighbor or to his cousin.

This would hardly be a slam dunk proof of the principle.  The objection could quickly be made, “Oh, he’s just trying to protect DNA that he shares.”  If there is a way to rule that out, I cannot think of it.  But I thought it was worth letting you know.  A different viewpoint can suggest a new kind of data to collect.  That can’t be all bad.

Let me know what you think.


M. Linton Herbert MD 

There have been 3,811 visitors so far.

Home page.