Losey_1999

Yu and Shepard 1have reported a preference for heavy women with high waist-to-hip ratios (WHR) in a culturally isolated popu-lation in southeast Peru. Their findings are interesting because a preference for low WHR is widespread in westernized popula-tions 2–5. However, we disagree with their argument that cultural invariance is neces-sary for an adaptionist interpretation of WHR preference.

WHR and waist circumference are posi-tively correlated with testosterone and neg-atively associated with oestrogen 6. Women with low WHR have better health and fertil-ity than women with high WHR 5. However,women in England and Texas with high

consumption rate on leaves with Bt pollen compared with leaves with untransformed pollen (P ǃ0.004).

The low consumption rates of larvae fed on leaves with Bt pollen led to slower growth rates: the average weight of larvae that survived to the end of the experiment on Bt -pollen leaves (0.16DŽ0.03g) was less than half the average final weight of larvae that fed on leaves with no pollen (0.38DŽ0.02g, P ǃ0.0001).

These results have potentially profound implications for the conservation of monarch butterflies. Monarch larvae feed exclusively on milkweed leaves 4; the com-mon milkweed, A. syriaca , is the primary host plant of monarch butterflies in the northern United States and southern Cana-da 5. Milkweed frequently occurs in and around the edges of corn fields, where it is fed on by monarch larvae 6. Corn fields

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5.Malcolm, S. B., Cockrell, B. J. & Brower, L. P . J. Chem. Ecol.15,819–853 (19).

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lightly misted with water. Pollen density was set to visually match densities on milk-weed leaves collected from corn fields. Peti-oles of individual leaves were placed in water-filled tubes that were taped into plas-tic boxes. Five three-day-old monarch lar-vae from our captive colony were placed on each leaf, and each treatment was replicated five times. Milkweed leaf consumption,monarch larval survival and final larval weight were recorded over four days.

Larval survival (56%) after four days of feeding on leaves dusted with Bt pollen was significantly lower than survival either on leaves dusted with untransformed pollen or on control leaves with no pollen (both 100%, P ǃ0.008) (Fig.1a). Because there was no mortality on leaves dusted with untransformed pollen, all of the mortality on leaves dusted with Bt pollen seems to be due to the effects of the Bt toxin.

There was a significant effect of corn pollen on monarch feeding behaviour (P ǃ0.0001) (Fig.1b). The mean cumula-tive proportion of leaves consumed per larva was significantly lower on leaves dusted with Bt pollen (0.57DŽ0.14, P ǃ0.001) and on leaves dusted with untransformed pollen (1.12DŽ0.09, P ǃ0.007) compared with consumption on control leaves without pollen (1.61DŽ0.09). The reduced rates of larval feeding on pollen-dusted leaves might represent a gustatory response of this highly specific herbivore to the presence of a ‘non-host’ stimulus. However, such a putative feeding deterrence alone could not explain the nearly twofold decrease in

weed leaf treatments: leaves with no pollen (light blue), leaves treated with untransformed corn pollen (green) and leaves dusted with pollen from Bt corn (dark blue). a,Mean (DŽs.e.m.) survival based on the proportion of larvae surviving in five replicates of each treatment. b,Mean (DŽs.e.m.) cumulative leaf consumption based on the total amount of leaf area consumed per larva in five replicates of each treat-ment. The amount of leaf area consumed per larva in each experimental unit was calculated for each time interval by dividing the amount of leaf area consumed in that interval by the number of larvae alive during the time interval. Cumulative consump-tion was calculated by summing the leaf area con-sumed per larva at each interval. Colours of lines correspond to those of the bars in a .

babies than low-WHR women 10). This might explain why traditional societies in which sons are valued over daughters may prefer tubular women, which is consistent with an adaptionist interpretation of these preferences.

J. T. Manning*, R. L. Trivers†, D. Singh‡,R.Thornhill§

*School of Biological Sciences,

University of Liverpool, Liverpool L69 3BX, UK e-mail: jtmann@liv.ac.uk

†Department of Anthropology, Rutgers University,New Brunswick, New Jersey 001-1414, USA ‡Department of Psychology, University of Texas,Austin, Texas 78712, USA

§Department of Biology, University of New Mexico,Albuquerque, New Mexico 87131-1091, USA

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7.Manning, J. T., Anderton, R. & Washington, S. M. J. Hum. Evol.31,41–47 (1996).

8.Singh, D. & Zambarano, R. J. Hum. Biol.69,545–556 (1997).9.Manning, J. T., Scutt, D., Wilson, J. & Lewis-Jones, D. I. Hum.Reprod.13,3000–3004 (1998).

10.Brown, J. E. et al . Epidemiology 7,62–66 (1996).

Evolutionary psychology suggests that a woman’s sexual attractiveness might be based on cues of reproductive potential. It has been proposed that a major determi-nant of physical attractiveness is the ratio between her waist and hip measurements (the waist-to-hip ratio, or WHR): for exam-ple, a woman with a curvaceous body and a WHR of 0.7 is considered to be optimally attractive 1–3, presumably because this WHR is the result of a fat distribution that maxi-mizes reproductive potential 4. It follows that the preference for a curvaceous body shape in women should be universal among men and not be culturally based, because natural selection presumably favours cues indicative of the most fertile body shape.Yu and Shepard have challenged this hypothesis 5. They tested the preferences of a culturally isolated tribe of Peruvian Indians (the Matsigenka) by using a set of line-drawn figures of women who varied in apparent body-mass index (BMI) and WHR 1. They claim that their results indi-cate a preference by this tribe for a tubular body shape, rather than the curvaceous shape favoured in the United States 5. How-ever, we believe that the conclusions of Yu and Shepard are undermined by a flawed assumption.

The drawings used by Yu and Shepard are arranged in three series 5: underweight,normal and overweight. Within each series,the BMI of each of the four figures is sup-posed to be held constant, while the WHR is varied by narrowing the waist. However,we believe that this assumption is false

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