Preferences for symmetry in faces change across the menstrual cycle

Symmetry in human male faces may be a cue to heritable fitness benefits and is found attractive. Preferences for facial masculinity, another proposed marker of genetic quality, have been found to vary in ways that may maximise evolutionary relevant benefits and masculinity is found to be of increased attractiveness at peak fertility across the menstrual cycle. Here we show that women prefer more symmetric faces at peak fertility (Study 1) and that such shifting preferences may be potentially strategic preferences as we found them to occur only for judgements concerning short-term relations and when women already had a partner (Study 2). Such preferences potentially indicate a strategy that maximises the quality of extra-pair/short-term partners or a quality dependent response to hormones. Such strategic preferences for symmetry may support the role of symmetry in signalling potential good-gene benefits. (C) 2007 Elsevier B.V. All rights reserved.</p

The molecular structure of tetra-tert-butyldiphosphine: an extremely distorted, sterically crowded molecule

The molecular structure of tetra-tert-butyldiphosphine has been determined in the gas phase by electron diffraction using the new DYNAMITE method and in the crystalline phase by X-ray diffraction. Ab initio methods were employed to gain a greater understanding of the structural preferences of this molecule in the gas phase, and to determine the intrinsic P–P bond energy, using recently described methods. Although the P–P bond is relatively long [GED 226.4(8) pm; X-ray 223.4(1) pm] and the dissociation energy is computed to be correspondingly small (150.6 kJ mol−1), the intrinsic energy of this bond (258.2 kJ mol−1) is normal for a diphosphine. The gaseous data were refined using the new Edinburgh structure refinement program ed@ed, which is described in detail. The molecular structure of gaseous P2But4 is compared to that of the isoelectronic 1,1,2,2-tetra-tert-butyldisilane. The molecules adopt a conformation with C2 symmetry. The P–P–C angles returned from the gas electron diffraction refinement are 118.8(6) and 98.9(6)°, a difference of 20°, whilst the C–P–C angle is 110.3(8)°. The corresponding parameters in the crystal are 120.9(1), 99.5(1) and 109.5(1)°. There are also large deformations within the tert-butyl groups, making the DYNAMITE analysis for this molecule extremely important