Why aren't rabbits green?

Wolfgang Wuster w.wuster at bangor.ac.uk
Wed Oct 16 04:44:26 EST 1996

On 16 Oct 1996, jos van den broek wrote:

> Why aren't rabbits green? Why aren't they armor-plated? Why aren't they 6' tall?
> Too bad that too many people still think about evolution in the old-fashioned 
> predator-prey relationships. Would it be good for a rabbit population that even 
> a feeble, green specimen could survive and have offspring? 

This is really a totally fallacious argument. If being green were
advantageous for survival, and a rabbit developed a green fur by chance
mutation, that gene would enhance survival (provided it is not linked to
other, deleterious, modifications), and would likely spread through the
population, whether for the ultimate good of the population or not. 

A species will not refrain from evolving a beneficial novelty simply in 
order to avoid overpopulation (c.f., Homo sapiens, who should know 

I suggest you read Richard Dawkins's book "The Selfish Gene" for a very 
readable discourse on this subject.

The real reason why green fur has not evolved in rabbits or other mammals 
is likely to be one of phylogenetic constraint - for any mammal to turn 
green, it would need to evolve, through chance mutation, a green colour. 
It seems that this has never happened in mammals, perhaps because there 
are no precursor molecules for a green pigment, or because mammalian fur 
structure does not allow green appearance through interference colours, 
as in reptiles. New traits do not appear as if by magic just because an 
animal needs them - they may appear by mutation, and if they enhance an 
animal's likelihood of passing genes on to the next generation, they may 
become fixed in the population, and may allow that population to exploit 
a new ecological niche.

Wolfgang Wuster
School of Biological Sciences, University of Wales, Bangor, UK
e-mail: w.wuster at bangor.ac.uk

Thought for the day: If you see a light at the end of the tunnel,
it is probably a train coming your way.

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