Nature article: Beard Chromodynamics


Figure 3 of Jansen & van Baalen (2006): An example of a snapshot of spatial beard chromodynamics.Here’s another peer-reviewed scientific article, published in Nature, that was probably published in the vicinity of April 1 due to its title:

Vincent A. A. Jansen and Minus van Baalen (2006). “Altruism through beard chromodynamics.” Nature 440, 663-666 (30 March 2006).

Abstract: The evolution of altruism, a behaviour that benefits others at one’s own fitness expense, poses a darwinian paradox. The paradox is resolved if many interactions are with related individuals so that the benefits of altruism are reaped by copies of the altruistic gene in other individuals, a mechanism called kin selection. However, recognition of altruists could provide an alternative route towards the evolution of altruism. Arguably the simplest recognition system is a conspicuous, heritable tag, such as a green beard. Despite the fact that such genes have been reported, the ‘green beard effect’ has often been dismissed because it is unlikely that a single gene can code for altruism and a recognizable tag. Here we model the green beard effect and find that if recognition and altruism are always inherited together, the dynamics are highly unstable, leading to the loss of altruism. In contrast, if the effect is caused by loosely coupled separate genes, altruism is facilitated through beard chromodynamics in which many beard colours co-occur. This allows altruism to persist even in weakly structured populations and implies that the green beard effect, in the form of a fluid association of altruistic traits with a recognition tag, can be much more prevalent than hitherto assumed.

The phrase “green beard” was invented by Richard Dawkins as an example of an inherited visual display that would indicate that its possessor also possessed a genetic disposition for altruisum, and thus could be trusted. This sounds like it might be a way for genetic altruism to evolve, but if such a “tag” can evolve, then “fakers” might also easily evolve, making the tag pointless. This paper explores a situation, however, where beards (of multiple colors, hence “beard chromodynamics”) and altruism persist. From the conclusion:

Our results imply that the scope for green beard genes is much wider than often assumed. This is for a number of reasons. First, altruism can be maintained without all the functions for tag, recognition and altruism having to reside in a single locus: loose coupling between a recognition allele and altruistic trait suffices. Second, our results suggest that rather than there being a single green beard gene in a population, one can expect to find a diversity of such genes, especially if the population is weakly structured. A possible reason that so few coloured beards have been reported is the concentration of research on highly structured populations in which the diversity of beard colours is predicted to be low. Our analysis leads to the testable hypothesis that diversity in recognition tags inversely correlates with average relatedness. This suggests that relatively easily observed tag diversity can serve as an indicator for the nature of the underlying social interactions. Third, to detect the green beard effect one should look for cases where tag and trait can dynamically associate. A tag that functions as a green beard in one instance need not be associated with altruism in another population or at another instance in time, which obviously has consequences for our capacity to detect green beards.


I colored my beard blue once for a party.

Billy Connolly dyed his one purple.

In primates, a beard and especially a green beard, is a secondary sexual trait limited to males whose body hair distribution makes a beard possible. Although several species of monkeys are named “bearded”, the beard only consists hair tufts on a furry face which does not continue to grow so is not a true beard. In addition to humans, the adult male orangutan does have a discernable Beard. Orangutans are solitary and the males have no input in child rearing or interaction in any family groups, so a green beard would be of little value and no variation in beard color has been observed in this species. Without family groups, Orangutans are not highly structured populations so this would seem to falsify the authors hypothesis.

Alturism in primate species is then limited to where it has been shown that bearded males have an investment in offspring. The primary effect is investment in nieces and nephews since they are guaranteed to be genetically related to the green bearded male and a secondary level of altruism is investment in offspring whose genetic relationship to the green bearded male is more distant. At the primary level of altruism, the green bearded male will recognize nieces and nephews, but the nieces and nephews might mistake any green bearded male as the altruistic uncle. A chromodynamic system might allow easier recognition of the correct uncle allowing a higher probability of selecting the correct uncle for protection. More distantly related offspring could run to any, color bearded male with a certain probability of protection (this probability would not differ between a monochromic and a polychromic system). This would seem to support the authors contention that a multi colored beard system would be stable in an unstructured population. The stability would be driven by the offsprings ability to detect the correct uncle and would therefore have a higher probability of protection in times of need. Of course a multi gene chromodynamic beard system would need to be in linkage disequilibrium with the altruism locus to maintain a functioning unit. The stability of such a system would be maintained by actions in 2 generations, altruistism in generation N, exhibited by the chromodynamiclly bearded uncle, and recognition of the chromodynamic beard in generation N+1, nieces and nephews.

It seems there are 2 possibilities that resulted in the occurrence of green beard phenomena, design and unguided, unplanned, unprovoked, unknown, natural, materialistic, mechanisms (uuuunmm).

The probability of a green beard arising and then altruism in linkage with a green beard gene would be P (joint occurrence) = P(green beard) x P(altruism) x P(linkage). As stated by the famous astronomer Percival Lowell. “For the intrinsic improbability of such a state of things arising from purely natural causes becomes evident on a moment’s consideration.” So the chance of a simple chromodynamic system evolving using uuuuunmm is essentially nil.

Alternatively it is possible that green headed monkeys may hold the answer.

Delta Pi Gamma (Scientia et Fermentum)

Bruce Thompson mentions nieces and nephews. Is “altruism” towards family really altruism? I guess I am confused. Doesn’t the green beard thing imply that their is a relationship, but it is a distant enough relationship that the relatives wouldn’t recognize their relatedness without the beard? I think that being good to your extended family is a recognized smart way of helping your genes and not really what this article is about.

I used the uncle, niece/nephew relationship because of the degree of genetic relatedness, contrasting this with the population as a whole. Obviously at the population level the number of genes shared in common is much much much lower, so the greater the genetic relationship the greater the advantage. That’s why I arbitrarily divided altruism into 2 tiers, primary and secondary.

It’s the little ones that are looking for the altruistic bearded male, not the other way around. The fact that recognizing an altruistic male is easier by looking for a specifically colored beard than by facial recognition, especially from a distance, has distinct advantages.

I also divided the system into 2 generations, the beard into 1 generation and the recognition system into the next generation. Selection would have to act across both generations jointly for any chromodynamic bearded system to be maintained.

My goals were to: 1. understand the article from the abstract and the discussion. 2. generate some discussion. 3. link green headed monkeys with uuummm.

Thanks for this piece. I was inspired to post an item on my blog about the tendency of scientists toward speculations unsupported by their data.

Davis Nelson Little Errors in the Beginning Blog

I was inspired to post an item on my blog about the tendency of scientists toward speculations unsupported by their data.

IDers, right?

Oh wait — they don’t have any science, do they.

Or any data.

About this Entry

This page contains a single entry by Nick Matzke published on April 1, 2006 3:26 PM.

Hebrew is the last common ancestor of all languages was the previous entry in this blog.

Good Math, Bad Math, and David Berlinkski is the next entry in this blog.

Find recent content on the main index or look in the archives to find all content.



Author Archives

Powered by Movable Type 4.381

Site Meter