My mission at the Centre for the Study of Cultural Evolution is to empirically study cultural change as though it is an evolutionary process. Unfortunately, one of my first insights was that cultural evolution is a very different process from that of biological evolution. Thus, I have refreained from assuming any sort of phylogenetic history for cultural traits and instead opted for studying actual recorded data - which means I have not been able to utilize the method package that I have utilized in my research as a biologist. If you are interested in the application of phylogenetic methodology, however, my friend and colleague Charlie Nunn has put together the definitive book on the subject.

My first empirical article is on a trait with absolutely no phylogenetic signal: the spread of democracy across the world (Lindenfors, Jansson & Sandberg 2011 pdf). You can read more about it here.

Other than an observation that chimp culture spreads via females (Lind & Lindenfors 2010 pdf), my work in this area is work in progress.

This aim of this research is to investigate the interesections between sociality, ecology and brain evolution in mammals, with special focus on sexual differences. There are thus far three studies finished, the first showing that changes in female group composition preceed changes in male group composition (Lindenfors, Fröberg & Nunn 2004 pdf), the second that the social brain hypothesis only applies to females (Lindenfors 2005 pdf), and the third that selection in relation to sex is a force to be reckoned with in primate brain evolution in general (Lindenfors, Nunn & Barton 2007 pdf).

Short summary of Lindenfors, Nunn & Barton (2007)

For a more comprehensive summary, click here.

The results of the latest study in the project (Lindenfors, Nunn & Barton 2007) indicate that differences between the sexes regarding the relative degrees of cooperation and competition have impacted primate brain architecture. Sexual selection has been central in shaping the primate brain.

We found that species with a higher degree of male-male competition over females have larger brain structures handling autonomic functions, sensory-motor skills, and neural pathways involving aggression, but smaller structures relating to aggression control.

We also replicated the results from Lindenfors (2005), showing that species where females cooperate in larger groups have larger neocortices. Curiously, there was no effect - even a hint of a negative effect - of typical male group size on neocortex size.

Note that we have NOT found, or even investigated, any differences between male and female brains! There exists no data to do such analysis at present.

My previous research has mainly focused on the consequences of sexual selection in three animal groups: primates, pinnipeds and shorebirds. This work has been based firmly on the theory first presented in Darwin's (1871) "The Descent of Man and Selection in Relation to Sex", where he states that sexual selection, in contrast to natural selection, "depends on the advantage which certain individuals have over other individuals of the same sex and species, in exclusive relation to reproduction" (Darwin, 1871, p.256). The angle I have taken is to apply current phylogenetic methodology to the issue.

The results can be summarized in the below set of graphs from my thesis that show the influence of sexual selection on body size evolution in the two sexes of (a) strepsirhine primates (Lindenfors & Tullberg 1998 pdf), (b) pinnipeds (Lindenfors, Tullberg & Biuw 2002 pdf), (c) haplorhine primates (Lindenfors & Tullberg 1998 pdf), and, (d) shorebirds (Lindenfors, Székely & Reynolds 2002 pdf).

Figure. Idealized graphs showing the four different responses to sexual selection for a) strepsirhine primates, b) pinnipeds, c) haplorhine primates, and, d) shorebirds for males (black) and females (gray). Sexual selection was correlated with the evolution of male size and sexual size dimorphism in all groups except strepsirhine primates. The path to male-biased size dimorphism has in all cases been through male size increase while the path to female-biased size dimorphism in shorebirds surprisingly turned out to be due to male size decrease. Female size has been affected by selection on males in haplorhine primates and shorebirds, but not in strepsirhine primates and pinnipeds, while male size has been affected by selection on females in shorebirds.

As can be seen, four different patterns unfold. Strepsirhine primates are relatively untouched by sexual selection - something else is clearly going on here - while males in all the other groups show substantial size increases when sexually selected. The really interesting thing, however, is what happens to the females. In pinnipeds the females remain at their original size, unaffected by the selection that is going on in the opposite sex. In haplorhine primates, on the other hand, females get dragged along - a pattern that a follow-up study (Lindenfors 2002 pdf) attributes to a possible genetic correlation and a significantly larger post-partum investment in more sexually selected species. In shorebirds the same thing happens as in haplorhis primates, but this time with a twist. It turns out that the reverse size dimorphism (here: larger females than males) in some shorebird species is caused by males decreasing in size more than females. The causes behind this latter pattern is not understood presently (at all). See my thesis for futher details on theses studies.

I have supervised two masters projects that have directly sprung from these studies. The first is an interspecific study on humans showing that there is no automatic relationship beween body mass and body mass dimorphism during human evolution (Gustafsson & Lindenfors 2002 pdf - part of Anders Gustafsson's masters thesis). The second is a study on primate canines indicating that these are actually under stronger selection than primate body mass (Thorén, Lindenfors & Kappeler 2005 pdf - to a large degree Sandra Thorén's masters thesis).

In this project , I am analyzing data to understand the ecology and evolution of parasites and pathogens in relation to carnivore mating and social systems. This is my post-doc project, which is beginning to lead to quite a few interesting results.

Thus far we have identified a host of ecological factors being important for parasite species richness in carnivores. These are mainly host body mass, latitude, geographic range and population density, but these differ depending on what type of parasite one is looking at (Lindenfors et al. 2007 pdf). Follow-up studies that I'm carrying out right now also indicate that there is more to the story than this. For example, since latitude and range indicate that there is something in the host species' ecology that is driving parasite diversity, we are currently investigating potentially important ecological factors. Also interesting is the biodiversity side of the story; exactly what happens to parasite richness when host species decline (Altizer, Nunn & Lindenfors 2007 pdf).

An analysis of the evolution of delayed implantation in carnivores (Lindenfors, Dalén & Angerbjörn 2003 pdf), showing that delayed implantation has a monophyletic (single unique) origin in carnivores.
A paper outlining a conceptual problem with using phylogenetic comparative methods to detect the existance of Rensch's rule in comparative data (Lindefors & Tullberg 2006 pdf ).
Then I have been a statistical "fault-finder" in a study evaluating Montessori education (Lindenfors 2007 pdf). (Note that I have no problems with Montessori education per se, just with the faulty study.)

Sonia Altizer - University of Georgia, Athens, USA.
Anders Angerbjörn - Stockholm University, Sweden.
Robert Barton - Durham University, UK.
Martin Biuw - University of St Andrews, UK.
Andrew Cunningham - Institute of Zoology, London, UK.
Love Dalén - School of Biological Sciences, University of London, UK.
John Gittleman - Director: Institute of Ecology, University of Georgia, Athens, USA.
Anders Gustafsson - Stockholm University, Sweden.
Fredrik Jansson - Centre for the Study of Cultural Evolution, Stockholm University, Sweden.
Kate Jones - Institute of Zoology, London, UK.
Peter Kappeler - German Primate Center, Göttingen, Germany.
Johan Lind - Centre for the Study of Cultural Evolution, Stockholm University, Sweden.
Charlie Nunn - Max Planck Institute, Leipzig, Germany & University of California, Berkeley, USA.
Rhiannon Pursall - University of Sheffield, UK.
Liam Revell - University of Massachusetts, Boston, USA.
John Reynolds - University of Norwich, UK.
Jens Rolff - University of Sheffield, UK.
Mikael Sandberg - Centre for the Study of Cultural Evolution, Stockholm University, Sweden.
Tamás Szekely - University of Bath, UK.
Birgitta Tullberg - Stockholm University, Sweden.
Lars Werdelin - Swedish Museum of Natural History, Sweden.