Developmental changes in the facial soft tissues

Short-base stereophotogrammetry was used to study differential growth and development of the soft tissues of the face. Thirteen facial parameters were measured at ages 9, 11, 13, 15, and 16 years on 170 facial contour maps selected from a mixed longitudinal study of 26 boys and 26 girls. Each parameter was measured three-dimensionally, and its developmental progress at the earlier stages was expressed as a percentage of its value at 16 years of age. Standing height development was assessed in the same way. Three parameters that measured soft tissues surrounding the eyes grew little but were very advanced in their development, following a "neural" pattern. The remaining facial parameters grew more but were less advanced, and standing height was least advanced. There appeared to be three separate patterns of development, "neural," "facial," and "skeletal." Girls were, in general, smaller than boys, but their development was more advanced when measured as a percentage of size at 16 years compared with boys.     

MHC-assortative facial preferences in humans

Individuals tend to choose mates who are sufficiently genetically dissimilar to avoid inbreeding. As facial attractiveness is a key factor in human mate preference, we investigated whether facial preferences were related to genetic dissimilarity. We asked female volunteers to rate the attractiveness of men from photographs and compared these results with individual genotypes at the major histocompatibility complex (MHC). In contrast to previously reported preferences based on odour, we found a non-significant tendency for women to rate MHC-similar faces as more attractive, suggesting a preference for cues to a self-similar MHC in faces. Further analysis revealed that male faces received higher attractiveness scores when rated by women who were MHC-similar than by MHC-dissimilar women. Although unexpected, this MHC-similar facial preference is consistent with other studies documenting assortative preferences in humans, including for facial phenotype.     

Cultural differences in preferences for facial coloration

Effects of facial coloration on facial attractiveness judgments are hypothesized to be “universal” (i.e., similar across cultures). Cross-cultural similarity in facial color preferences is a critical piece of evidence for this hypothesis. However, only two studies have directly compared facial color preferences in two cultures. Both of those studies reported that White UK and Black African participants showed similar preferences for facial coloration. By contrast with the cross-cultural similarity reported in those studies, here we show cultural differences in the effects of facial coloration on Chinese and White UK participants' facial attractiveness judgments. While Chinese participants preferred faces with decreased yellowness to faces with increased yellowness, White UK participants preferred faces with increased yellowness to faces with decreased yellowness. Chinese participants also demonstrated weaker preferences for facial redness and stronger preferences for facial lightness than did White UK participants. These results suggest that preferences for facial coloration are not universal.     

Negative frequency-dependent preferences and variation in male facial hair

Negative frequency-dependent sexual selection maintains striking polymorphisms in secondary sexual traits in several animal species. Here, we test whether frequency of beardedness modulates perceived attractiveness of men''s facial hair, a secondary sexual trait subject to considerable cultural variation. We first showed participants a suite of faces, within which we manipulated the frequency of beard thicknesses and then measured preferences for four standard levels of beardedness. Women and men judged heavy stubble and full beards more attractive when presented in treatments where beards were rare than when they were common, with intermediate preferences when intermediate frequencies of beardedness were presented. Likewise, clean-shaven faces were least attractive when clean-shaven faces were most common and more attractive when rare. This pattern in preferences is consistent with negative frequency-dependent selection.     

The influence of infant facial cues on adoption preferences

Trivers’s theory of parental investment suggests that adults should decide whether or not to invest in a given infant using a cost-benefit analysis. To make the best investment decision, adults should seek as much relevant information as possible. Infant facial cues may serve to provide information and evoke feelings of parental care in adults. Four specific infant facial cues were investigated: resemblance (as a proxy for kinship), health, happiness, and cuteness. It was predicted that these cues would influence feelings of parental care for both sexes, but that resemblance would be more important for men than women because of the importance of paternity uncertainty in the ancestral environment. Seventy-six men and 76 women participated in a hypothetical adoption task in which they made judgments of infant faces. Average zero-order, partial, and component score correlations all revealed that men placed primary emphasis on cues of resemblance, while women placed primary emphasis on cues of health and cuteness (cues of infant quality). The correlations also showed that men placed a significantly greater emphasis on cues of resemblance than did women. This research was supported by a Queen’s University Graduate Award (first author) and a Senior Research Fellowship from the Ontario Mental Health Foundation (second author). Anthony Volk is a Ph.D. candidate at Queen’s University, studying parental investment. Vernon L. Quinsey is a professor of psychology and psychiatry at Queen’s University. His research focuses on forensic and evolutionary psychology. An erratum to this article is available at .     

Developmental changes in the facial morphology of the Borneo orangutan (Pongo pygmaeus): possible signals in visual communication

Orangutans display remarkable developmental changes and sexual differences in facial morphology, such as the flanges or cheek-pads that develop only on the face of dominant adult males. These changes suggest that facial morphology is an important factor in visual communication. However, developmental changes in facial morphology have not been examined in detail. We studied developmental changes in the facial morphology of the Borneo orangutan (Pongo pygmaeus) by observing 79 individuals of various ages living in the Sepilok Orangutan Rehabilitation Centre (SORC) in Malaysia and in Japanese zoos. We also analyzed photographs of one captive male that were taken over a period of more than 16 years. There were clear morphological changes that occurred with growth, and we identified previously unreported sexual and developmental differences in facial morphology. Light-colored skin around the eyes and mouth is most prominent in animals younger than 3 years, and rapidly decreases in area through the age of approximately 7 years. At the same time, the scattered, erect hairs on the head (infant hair) become thick, dense hairs lying on the head (adult hair) in both sexes. The results suggest that these features are infant signals, and that adult signals may include darkened face color, adult hair, whiskers, and a beard, which begin to develop after the age of approximately 7 years in both sexes. In females, the eyelids remain white even after 10 years, and turn black at around the age of 20; in males, the eyelids turn black before the age of 10. The whiskers and beards of adults are thicker in males than in females, and are fully developed before the age of 10 in males, while they begin to develop in females only after approximately 20 years. White eyelids and undeveloped whiskers and beards may be visual signals that are indicative of young adult females. Our results also show that the facial morphology of the unflanged male is similar to that of the adult female, although it has also been pointed out that unflanged males resemble younger individuals.     

Developmental changes in crossover frequency in Arabidopsis

Parental genomes are generally rearranged by two processes during meiosis: one is the segregation of homologous chromosomes and the other is crossing over between such chromosomes. Although the mechanisms underlying chromosome segregation and crossing over are well understood because of numerous genetic and molecular investigations, their contributions to the rearrangement of genetic information have not yet been analysed at a genome-wide level in Arabidopsis thaliana. We established 343 CAPS or SSLP markers to identify polymorphisms between two different Arabidopsis ecotypes, Col and Ler, which are distributed at an average distance of approximately 400kb between pairs of markers throughout the entire genome. Using these markers, crossover frequencies and chromosome segregation were quantified with respect to sex and age. Our large-scale analysis demonstrated that: (i) crossover frequencies during pollen formation were 1.79 and 1.37 times higher than those during megaspore formation in early and late flowers, respectively (P<0.001); (ii) the crossover frequencies during pollen formation were not significantly different between early and late flowers of main shoots (P>0.05), whereas the frequencies increased 1.30 times with shoot age during megaspore formation (P<0.001); (iii) the effect of aging depended on the developmental age of the individual shoot rather than on the age of the whole plant; and (iv) five chromosomes were randomly selected and mixed during meiosis.     

Developmental changes in mouse brain polyamine metabolism

Mouse brain ornithine decarboxylase (ODC) activity is high at the time of birth, whereas S-adenosyl-l-methionine decarboxylase (SAM-DC) activity is low. ODC activity, and putrescine, spermidine and spermine concentrations decline rapidly during postnatal development to the low level characteristic of mature brains, while SAM-DC activity behaves in the opposite manner. The fluctuations in mouse brain polyamine metabolism are in accord with those found in the rat. The apparentK _m values of ODC and SAM-DC for their substrates decline parallel with the decrease of substrate and product concentrations during ontogeny suggesting substrate and/or product dependent regulation of polyamine synthesis in the developing brain.     

Developmental changes in cardiac recovery from anoxia-reoxygenation

The developing cardiovascular system is known to operate normally in a hypoxic environment. However, the functional and ultrastructural recovery of embryonic/fetal hearts subjected to anoxia lasting as long as hypoxia/ischemia performed in adult animal models remains to be investigated. Isolated spontaneously beating hearts from Hamburger-Hamilton developmental stages 14 (14HH), 20HH, 24HH, and 27HH chick embryos were subjected in vitro to 30 or 60 min of anoxia followed by 60 min of reoxygenation. Morphological alterations and apoptosis were assessed histologically and by transmission electron microscopy. Anoxia provoked an initial tachycardia followed by bradycardia leading to complete cardiac arrest, except for in the youngest heart, which kept beating. Complete atrioventricular block appeared after 9.4 +/- 1.1, 1.7 +/- 0.2, and 1.6 +/- 0.3 min at stages 20HH, 24HH, and 27HH, respectively. At reoxygenation, sinoatrial activity resumed first in the form of irregular bursts, and one-to-one atrioventricular conduction resumed after 8, 17, and 35 min at stages 20HH, 24HH, and 27HH, respectively. Ventricular shortening recovered within 30 min except at stage 27HH. After 60 min of anoxia, stage 27HH hearts did not retrieve their baseline activity. Whatever the stage and anoxia duration, nuclear and mitochondrial swelling observed at the end of anoxia were reversible with no apoptosis. Thus the embryonic heart is able to fully recover from anoxia/reoxygenation although its anoxic tolerance declines with age. Changes in cellular homeostatic mechanisms rather than in energy metabolism may account for these developmental variations.     

Developmental changes in Malpighian tubule fluid transport

Developmental changes in Malpighian tubule fluid transport were studied using in vitro and in situ preparations from timed larval, pupal and adult skipper butterflies (Calpodes ethlius). The ability to transport fluid and the rate of fluid secretion depend on the developmental stage and the physiological state. Larval tubules are permanently switched on, do not require a diuretic hormone and transport fluid at an increasing rate as the larvae feed and grow. Fluid transport continues at larval-larval moults but is switched off 24 hr before pupal ecdysis. No secretory activity occurs during the first half of the pupal stage when the tubules are remodelled for adult function. The resumption of fluid transport midway through the pupal stage is in preparation for a rapid diuresis at adult emergence. High rates of fluid secretion are associated with feeding or drinking in adults.     

Developmental changes in upper airway dynamics.

Normal children have a less collapsible upper airway in response to subatmospheric pressure administration (P(NEG)) during sleep than normal adults do, and this upper airway response appears to be modulated by the central ventilatory drive. Children have a greater ventilatory drive than adults. We, therefore, hypothesized that children have increased neuromotor activation of their pharyngeal airway during sleep compared with adults. As infants have few obstructive apneas during sleep, we hypothesized that infants would have an upper airway that was resistant to collapse. We, therefore, compared the upper airway pressure-flow (V) relationship during sleep between normal infants, prepubertal children, and adults. We evaluated the upper airway response to 1). intermittent, acute P(NEG) (infants, children, and adults), and 2). hypercapnia (children and adults). We found that adults had a more collapsible upper airway during sleep than either infants or children. The children exhibited a vigorous response to both P(NEG) and hypercapnia during sleep (P < 0.01), whereas adults had no significant change. Infants had an airway that was resistant to collapse and showed a very rapid response to P(NEG). We conclude that the upper airway is resistant to collapse during sleep in infants and children. Normal children have preservation of upper airway responses to P(NEG) and hypercapnia during sleep, whereas responses are diminished in adults. Infants appear to have a different pattern of upper airway activation than older children. We speculate that the pharyngeal airway responses present in normal children are a compensatory response for a relatively narrow upper airway.     

Developmental changes in rat liver alcohol dehydrogenase

Hepatic alcohol dehydrogenase activity and mass content change coordinately during development in male rats. Enzyme activity and mass content increase continuously after birth to 100 and 80% of maximal values within 6 weeks (2.6 ± 0.4 μmole/min/g liver and 92 ± 20 μg/g liver), respectively. When expressed per milligram of soluble proteins, both parameters peak at 3 weeks (0.052 ± 0.002 μmole/min/mg protein and 2.0 ± 0.4 μg/mg protein) and then decrease gradually to plateau levels. These decreases probably arise from a “surge” in soluble liver protein levels that occurs after weaning. Similar developmental patterns also occur in female rats. These findings are the first quantitative measurements of this enzyme in developing animals.     

Correlated preferences for facial masculinity and ideal or actual partner's masculinity

Studies of women's preferences for male faces have variously reported preferences for masculine faces, preferences for feminine faces and no effect of masculinity-femininity on male facial attractiveness. It has been suggested that these apparently inconsistent findings are, at least partly, due to differences in the methods used to manipulate the masculinity of face images or individual differences in attraction to facial cues associated with youth. Here, however, we show that women's preferences for masculinity manipulated in male faces using techniques similar to the three most widely used methods are positively inter-related. We also show that women's preferences for masculine male faces are positively related to ratings of the masculinity of their actual partner and their ideal partner. Correlations with partner masculinity were independent of real and ideal partner age, which were not associated with facial masculinity preference. Collectively, these findings suggest that variability among studies in their findings for women's masculinity preferences reflects individual differences in attraction to masculinity rather than differences in the methods used to manufacture stimuli, and are important for the interpretation of previous and future studies of facial masculinity.