Download Source: Centre National De La Recherche Scientifique

Source: Centre National De La Recherche Scientifique
Why Are Animals Altruistic?
Researchers at the Laboratoire d'Écologie at the University Pierre and Marie Curie (Ecole
Normale Supérieure/CNRS) and the Royal Holloway College (London, United Kingdom)
have just explained the evolution of altruistic behavior in animals.
In nature animals have been observed cooperating, and the detection of a genetic predisposition to this
type of behavior contradicts Darwin's theory of evolution which predicts a better survival rate for the most
selfish animals. The use of mathematic modeling has provided a new explanation for the surprising
persistence of this type of behavior which appears, at first sight, to be detrimental to the animal adopting
it.
This work is published in Nature on 30 March 2006.
Even today Darwin's Theory of Evolution continues to give rise to scientific debates. One of the subjects
which triggers such debate is that of altruism, regularly observed in several animal classes. This type of
behavior consists of helping another animal, at the expense of the helper's well-being. In general altruists
only help family members and in this way the behavior contributes indirectly to the transmission of a part
of their genes (selection of the immediate family).
However “selfish” individuals may “cheat” and receive help while giving none in return. What to make of
these cheaters, who have an advantage, and hence can better transmit their genes?
W.D. Hamilton, one of the first proponents of the modern theory of evolution, assumed that the altruists
could identify each other. However, this does not take into account the incredible capacity of all living
beings to adapt. The so-called “green beard” theory illustrates this question: the theory posits that altruists
could have green beards, and thus be recognized by other altruists. The few selfish individuals of the
same species which also have green beards will effectively have the opportunity to cheat…and will
succeed at the expense of the altruists.
Real life examples seem to uphold this theory because such situations exist in the natural world. Of
course they do not involve green beards but, for example, ants secreting scents or molecules produced
by bacteria.
Vincent Jansen and Minus Van Baalen of the Laboratoire d'écologie at the University of Pierre and Marie
Curie (ENS/CNRS) have just introduced a new factor which supports Hamilton's explanation. Using
mathematical modeling, they have demonstrated that cooperation can be selected for during the evolution
of a species if the altruists can change the “color of their beards” when the cheaters become too
numerous. In this game of evolutionary cat and mouse the altruists are always one step ahead of the
cheaters.
This discovery explains the enigma created by the detection of genes leading to a predisposition in
altruists to recognize each other.
Reference:
Vincent Jansen & Minus Van Baalen. Altruism through beard chromodynamics. Nature, 30 March 2006.
Editor's Note: The original news release can be found here.
http://www.sciencedaily.com/releases/2006/04/060404201741.htm