No one smells good to everyone: it depends on who is sniffing whom

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Laureen Mitchell
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1 No one smells good to everyone: it depends on who is sniffing whom Wedekind and Furi, 1997

2 Proposed stages in the evolution of hormonal pheromones Pheromones evolved from compounds originally having other uses: hormones, host plant odours, chemicals released on injury, or waste products.

3 Number of carbon atoms in pheromones used as alarms, long range sex attractants, and contact pheromones. (Contact pheromones of a fly)

4 Primer and releaser pheromones

5 Major Histocompatibility Complex and finding one s mate. Set of genes that code for cell surface proteins involved in self and non-self recognition. In humans, there are at least 82 genes that are extremely polymorphic. MHC types can be distinguished by odour. Odours are used as a marker for the degree of kinship between two individuals.

6 The specific individual odour is the sum of the interplay of MHC-determined products, odours produced by the genetic background of the individual and its commensal microbial flora.

7 How do MHC genes influence individual odour?

8 MHC and mate choice. Advantages of dissortative mating - increased diversity of MHC alleles in offspring. - reduced inbreeding depression - higher implantation rates if fetus and mother differ in MHC. (Egid and Brown, 1989; Manning et al., 1992)

9 Mice pups cross-fostered into MHC-dissimilar families reverse their mating preferences. Mating Preference (Penn and Potts, 1998)

10 Alarm Pheromones

11 Alarm Pheromones Most highly developed in eusocial insects!

12 A. C. Giant hornet scout B. Bee response is triggered by the hornet s marker pheromone.

13 Predators to the rescue.

14 Synomones

15 Allomones

16 Allomones Atemels pubicollis Appeasement gland and adoption glands

17 Pheromones in humans

18 Vomeronasal organ is specific to pheromones in many species. Humans appear not to have it. VNO is present in basal vertebrates.

19 Pheromone synchronization of menstrual cycle.

20 MHC and mate choice. (Wedekind et al Proc. Roy. Soc. Lond. B. 260, )

21 People with a given MHC tended to choose the same perfume ingredients, and these were different from those chosen by people with a different MHC. This was true only when the subjects were asked to choose a perfume for themselves. (Milinski and Wedekind, Behavior. Ecol. 12, )

face Artificial symmetrical face constructed from

22 Fluctuating asymmetry Artificial symmetrical face constructed from left-hand side of image of real face Artificial symmetrical face constructed from right-hand side of image real face Real asymmetrical face

23 Int J Sports Med Apr;19(3): Symmetry and performance in middle distance runners. Manning JT, Pickup LJ. School of Biological Sciences, University of Liverpool, UK. Deviations from perfect symmetry in paired traits such as ear size and nostril width may indicate developmental instability and/or short-term fluctuations in hormones. In both cases symmetry is thought to be optimal and to indicate high phenotypic quality. The purpose of this work was to determine the relationship between symmetry and performance in middle-distance runners. Fifty male subjects participated in this study. Deviations from perfect bilateral symmetry were measured in seven traits; ear size, nostril width, 2nd to 5th digit length and wrist width. After measurements were made the subjects were ranked for athletic ability and they reported their best 800 metre and 1500 metre times. Symmetric subjects had higher rankings for athletic ability (nostrils, p<0.001 and ears, p< 0.001), lower best 800 metre times (nostrils, p<0.05 and ears, p<0.01) and lower best 1500 metre times (3rd digit, p<0.01 and ears, p<0.05) than asymmetric subjects. This conclusion remained essentially the same after Bonferroni adjustment for multiple tests and when experience and age were controlled for in multiple regression tests. We conclude that symmetry in traits such as nostrils and ears indicates good running ability. It may therefore be useful in predicting the future potential of young athletes. Nevertheless, symmetry as an indication of an individual s health and genetic quality is a controversial idea. Many studies find negative results.

24 Normally ovulating women preferred the scent of symmetrical men during their period of peak fertility. Such women showed no preference for symmetry during periods of low fertility in their cycle. Gangestad and Thornhill, 1998, Proc. Roy. Soc. Lond. B 265, Picasso, self portrait, 1907

Last Lecture. Cont. Being Social, Chapter 3 Evolution of Human Behavior, Chapter 14

Last Lecture. Cont. Being Social, Chapter 3 Evolution of Human Behavior, Chapter 14 Last Lecture Cont. Being Social, Chapter 3 Evolution of Human Behavior, Chapter 14 Is there a reason to be social? What are the benefits of sociality? 1. Cooperation, both benefit 2. Postponed cooperation