Analysis and Replication of
This page provides more information about the system we analysed in our
Which in 2011 was updated as a book chapter:
It includes code so you can check our replication and watch it run
yourself, and a scientific critique of Hemelrijk's
theories of social structure and primate dominance. Briefly, the
DomWorld results all hinge on two assumptions:
Neither of these conditions holds for many if not most varieties of
- that there is always at least some chance that any animal in a
might beat any other animal in a dominance interaction.
- that ranks in the dominance hierarchy change frequently as a
consequence of unexpected outcomes from these interactions (low-ranking
animals beating high-ranking ones).
Charlotte Hemelrijk's DomWorld (which she inherited from her supervisor
Paulien Hogeweg) is one of
the most widely published agent-based models in biology. Although
Hogeweg developed it as part of her research into bee colonies,
Hemelrijk has used it to explain dominance interactions and social
structure in a variety of species, primarily primates.
Because we were interested in studying primate social structure as
well, and because a number of the primatologists we worked with had
theories that contradicted the DomWorld model, we decided to analyze
it. We first had to replicate the model, partly because there was
no publicly-available version, but also because this is good scientific
Several MSc and undergraduate students at Bath tried to replicate
DomWorld from Hemelrijk's papers, but none got quite the same behavior
she reported. Finally a PhD student, Hagen Lehmann, found the
missing piece. He fixed the best replication we had so far (by
Jing Jing Andrea Wang), and we presented the paper at two
workshops, and published a paper in a workshop proceedings.
In that paper, we identified six questions that would test the validity
of Hemelrijk's use of DomWorld to describe primate social
After the workshop, we were able to visit the
laboratory of Bernard
Thierry, who helped us answer the questions. We found several
problems with the model. The most significant is that DomWorld predicts
that primates' dominance rank should be in a constant rate of
flux. However, in most primate species, a female's rank is
determined entirely by her mother's rank and her birth order relative to her sisters. On very
rare occasions an entire matrilinial line will change order, but this
is really an exceptional event. This may be a better model of the few species
like chimpanzees where females migrate between social groups, but for macaques (a widely-used model genus for
studying primate social order) it is not realistic. In
egalitarian macaque species, even changes in male rank happen very
infrequently, mostly in response to the aging or migration of males.
On the other hand, we also found that even if these problems were
removed from the model, some of the other characteristics (such as its
explanation for the spatial location of dominant animals within the
troop) still hold.
One problem with code is that the computer systems on which we run it keep
changing. Thus the actual code we ran for the results shown in our paper is
harder to run now unless you dig up the original research platforms.
Here is the exact code we used for the PTRS-B article.
Hagen Lehmann and Jing Jing Wang's replication of Hemelrijk's DomWorld
code. To run that program, you should download version 2.2pre2 of NetLogo, although it may also
work in version 3 (but certainly not 4).
Yasushi Ando's Predation Simulation
includes a second replication of Hemelrijk's DomWorld. The
simulator is written in SmallTalk and must
be executed from within Squeak version
3.7, which is available here.
Here is newer code for easier replications.
page author: Joanna
Page last updated 14 December 2008.
Current Code last updated 6 March 2011
for NetLogo 4.1.1