How and why we should move beyond natural selection in museums to tackle teleology.

Background: Museum displays commonly use a "VIST" approach (Variation, Inheritance, Selection, and Time) to explain evolution to visitors. I contend that this framework, by focusing narrowly on natural selection, unintentionally reinforces intuitive teleological thinking and a "survival of the fittest" mentality. Exhibits that incorporate all the forces (or mechanisms) of evolution will instead challenge visitors' preconceptions and enable them to develop a deeper understanding of evolution. In particular, visitors will appreciate that evolution is not progressive, with modern humans as the "most evolved" species. Results: Explicit and implicit description of the forces of evolution is surveyed in 12 museums: 4 in Texas, 7 elsewhere in the U.S., and the Natural History Museum in London. Museum exhibits focus primarily on natural selection (explicit in 10 of 12) and often mention mutation (explicit in 7). Only the American Museum of Natural History in New York, in my sample, provides an explicit explanation of genetic drift. Conclusions: Heavy emphasis on natural selection and limited explanation of stochastic forces contributes to an impoverished view of evolution. Exhibits should more effectively convey the complexity of microevolution. Computer simulations showing the interactions of evolutionary forces can accomplish this goal.

Human manual distal phalanges from the Middle Stone Age deposits of Klasies River Main Site, Western Cape Province, South Africa.

Two new distal manual phalanges from the Middle Stone Age deposits of Klasies River Main Site are described. One (SAM-AP 6387) likely derives from ray II or ray III, whereas the other (SAM-AP 6388) is from the thumb. Both derive from a late adolescent or fully adult individual. They were recovered by H. Deacon from the same stratigraphic unit (submember W or possibly submember R) of the Shell and Sand Member of Cave 1, which places them between 100 and 90 ka. Both are comparatively small elements, and the possibility that they came from the same hand cannot be discounted at this time. These bones add to the meager and all too fragmentary postcranial human fossil sample from the Late Pleistocene of South Africa. These two specimens provide some additional evidence pertaining to the morphological attributes of the distal phalanges of the Middle Stone Age inhabitants of South Africa. Together with the distal pollical phalanx from Die Kelders (SAM-AP 6402), they are relatively small in comparison with homologs from recent human samples as well as Late Pleistocene specimens from Eurasia. Given their small sizes, the distal pollical phalanges from Klasies and Die Kelders are not dissimilar to Holocene Khoesan homologs. As expected, the Klasies elements differ noticeably from Neandertal homologs, especially in the narrowness of their shafts and distal tuberosities.

Single (sub)species then and now: An examination of the nonracial perspective of C. Loring Brace.

C. Loring Brace's writings on the concept of race have been among the most influential within anthropology. A review of the development of Brace's perspective on race shows that his philosophical approaches to fossil and modern human variation are consistent and integrated. Brace's views on race are compared with those of Ashley Montagu and Frank Livingstone, who also proposed eliminating "race" from anthropology, and with those of Stanley Garn and Alice Brues, who accepted "racial" subdivisions of humans. Carleton Coon's writings are more divergent; the aftermath of the publication of his Origin of Races highlights significant political tensions of the 1960s that intersected with scientific changes in anthropology emanating from the Evolutionary Synthesis. Recent forensic and "no race" positions are compared to explore their differences and the possibility of reconciliation, and the role of Brace and others in combating proposals of intellectual differences among human groups is discussed. While a spectrum of anthropological opinion regarding race exists, the commonalities are sufficient to allow valuable, united commentary emphasizing the complexity of modern human cultural and biological variation.

Twenty-First Century "Eugenics"?: The Enduring Legacy.

Despite pronounced changes in genetic knowledge and technology, the post-World War II philosophical stance on "eugenics" has not changed substantially. By the mid-1900s, as classical eugenics became less genetically naive and the medical profession became increasingly oriented toward disease prevention, a reformed eugenics had greater appeal. Eugenics' surviving influence on medical genetics is best seen in the field of genetic counseling, a discipline that serves prospective parents and families at risk of genetic abnormalities, and whose origins reveal close ties to population genetics. This article examines the ideal of nondirective counseling, genetic screening for disease, concerns regarding the quality of children, and the potential to select the sex and other characteristics of future offspring in order to indicate the complexity of ethical issues in modern genetic counseling. Modern "eugenics" is prevention-focused and has, importantly, eschewed outmoded and invidious "racial" distinctions, but these seminal tendencies are evident by the mid-20th century.

An examination of proportional root lengths of the mandibular canine and premolars near the time of eruption.

INTRODUCTION: To make treatments more efficient, orthodontists require a more precise means of estimating tooth eruption. The purpose of this article was to extend the information derived from dental staging techniques by incorporating direct measurements of root lengths for 3 mandibular teeth: the canine and the 2 premolars. METHODS: The full sample consists of 227 panoramic films from 77 female patients and 229 films from 74 male patients treated at a practice in Texas. A subsample of paired preeruption and posteruption films was examined in greater detail (46 subjects for the canine, 42 for the first premolar, and 46 for the second premolar). RESULTS: Canines will most likely have root length ([root length/total tooth length] × 100) of approximately 70% and premolars will have approximately 65% near the time of alveolar eruption. In addition, the walls of the root canal will probably approach a parallel configuration at the time of eruption. CONCLUSIONS: The percentage of root length, along with root canal parallelism, should allow improved prediction of eruption timing.

Growth in root length of the mandibular canine and premolars in a mixed-longitudinal orthodontic sample.

Numerous studies of dental development focusing on eruption (clinical emergence) exist in the literature, but fewer studies examine dental development as a process extending across years or decades, and root development is commonly assessed using fractional root lengths. Here, we examine the growth of mandibular canine and premolar roots in a mixed-longitudinal sample of orthodontic patients (77 females and 74 males) from north central Texas. Multilevel models are generated for root lengths as a percentage of total tooth lengths (within films) as well as for absolute root lengths (across films). As a percentage of tooth length, roots grow with decreasing velocity through time between 7 and 14 years of age. More complex patterns appear for absolute growth in root length, with girls showing an earlier maximum growth rate for the canine than for the premolars. Substitution of dental age for chronological age reduces between-subject variation (assessed at age 11), especially for boys. A better understanding of dental maturation, including root length growth, should allow improved prediction models.

Stature estimation of 3-10-year-old children from long bone lengths.

Estimation of stature in adult forensic cases with available long bones of the limbs is routine, but such estimation is less common in subadult cases. Long bones from subadult cases are often used to estimate age, but in some instances stature may be helpful or even critical for identification. Few published regression equations exist for consultation in such cases. Data from the longitudinal growth study conducted by the Child Research Council in Denver in the mid-1900s are utilized to produce dual-sex and single-sex regression equations for the six long bones of the limbs (humerus, radius, ulna, femur, tibia, and fibula) and for the combined femur+tibia length. All measurements are from radiographs and are of diaphyseal length. Examples show that similar results can be obtained using a two-step process of "ballpark" estimation from published tables of the Denver data, but these new regressions allow a one-step standard error estimate for the means. Regressions are further compared with those previously published by Finnish researchers, which are generally broadly comparable. More routine stature estimation in subadult cases is encouraged both as an aid to possible identification and as a test of the available regression equations.

Comparability of radiographic and 3D-ultrasound measurements of facial midline tissue depths.

As a second step in our three-dimensional (3D) ultrasound research on facial tissues, orthodontic patients with available lateral cephalographs (radiographs) allowing measurements of tissues along the midline of the face were recruited for ultrasound scanning. Comparison of three points on the upper lip (A-point), chin (B-point), and nose (nasion) produced differences of varying magnitude between radiographic and ultrasound measurements, with the B-point measurement being clearly affected by head orientation. Concordance was better for A-point and best for nasion. Although extension of two-dimensional (2D) ultrasound scanning of facial tissues to 3D scanning for forensic and surgical reconstructive purposes remains a worthy goal, it must be recognized that because of the differences in technique, measurements obtained from the different visualization modalities at present vary in their comparability.

Longitudinal models of long bone growth during adolescence.

Data from the Child Research Council (Denver, CO) were utilized to model longitudinal adolescent growth of the humerus, radius, femur, and tibia for 36 girls (10-16 years) and 33 boys (10-17 years). Multilevel modeling procedures were used to estimate variation, covariation, and the polynomial parameters necessary for generating growth curves. At age 10, long bone lengths for girls and boys are similar; by age 16, each of the boys' arm bones is about 20 mm longer and each of their leg bones is about 30 mm longer. Due to the earlier maturation of girls, the models show the length of each of their long bones exceeding that of boys to some degree during some period of adolescence. Peak velocities for leg bones are attained earlier than those for arm bones; in both sexes, age at humeral peak velocity coincides with age at peak height velocity (PHV). At age 13, correlations among lengths and among velocities of bones are strong to moderate, and girls consistently display higher variation than do boys for both long bone length and growth velocity. Considered relative to the average velocity of each bone's growth, the tibia is the most variable of the four long bones at age 13 years.

Variation in longitudinal diaphyseal long bone growth in children three to ten years of age.

Data from the Child Research Council (Denver, CO) were analyzed to model longitudinal growth changes in the humerus, radius, femur, and tibia in 31 boys and 36 girls between 3 and 10 years of age. Multilevel modeling of growth changes allowed efficient estimates of bone size and bone growth variation to be obtained as well as comparisons of growth patterns within and between limbs. The long bones displayed decelerating growth through time, with greater velocities for the larger lower limb (vs. smaller upper limb) bones and the larger proximal (vs. smaller distal) elements within limbs. Coordination for bone size and growth velocity is good both within and between limbs, suggesting a common growth control mechanism that should make growth prediction possible. Adjusted for size, the tibia appears to be the most variable of these four long bones, which may be due to a combination of environmental effects and flexible growth potential.

Skeletal age, dental age, and the maturation of KNM-WT 15000.

The skeleton of the Homo erectus boy from West Lake Turkana, Kenya (KNM-WT 15000), is remarkably complete, and this individual has thus provided a case study for several researchers examining Homo erectus growth. Using data from a longitudinal study of Montreal French-Canadian children, it is shown that while dental and skeletal ages match reasonably well at the level of a sample of children, individuals can display differences between skeletal and dental ages of 2 years or more. Furthermore, the relationship between these two markers may change over time in individual children. It is also possible to find children with patterns of dental maturation similar to KNM-WT 15000's pattern in the Montreal sample. Therefore, neither the discrepancy between skeletal age and dental age alone nor the pattern of dental maturation as assessed by dental stages precludes a human-like pattern of growth, including an adolescent growth spurt, for this individual. Some indicators (e.g., estimated body size for predicted age, and enamel formation) do suggest possible growth-patterning differences from modern humans, and therefore earlier maturation is a reasonable hypothesis, but caution is warranted, given the large degree of modern human variation in developmental markers and the inherent uncertainty in precise estimation of KNM-WT 15000's maturational parameters.

A new technique for three-dimensional ultrasound scanning of facial tissues.

We report the development of an ultrasonic facial scanning technique that allows for the visualization of continuous contours without deforming surface tissues. Adhesive markers are placed on the face to enable measurement of facial tissue thicknesses at specific landmarks. The subject immerses the face in a clear plastic box filled with water for about 20 seconds while the researcher moves the transducer along the bottom of the box, guiding transducer movement by watching the facial image in a mirror placed below. 3D Echotech software (1) builds the images from sequentially acquired 2D frames. Reliability of repeat measurements at landmarks is good, and individual tissues (skin, subcutaneous, muscle) can be distinguished. The method is simple, reliable, less expensive and less time consuming than alternatives such as magnetic resonance imaging (MRI). It is applicable in both research and clinical contexts.

Midsagittal facial soft-tissue growth of French Canadian adolescents.

This study examines changes in 12 midline soft-tissue thicknesses from the forehead, nose, lip, and chin regions in girls and boys from 10 to 16 years of age. The soft-tissue changes are compared to changes in two hard-tissue distances (sella-nasion and nasion-menton). The subjects are from a mixed-longitudinal sample studied at the Montreal Human Growth Research Center in the 1960s and 1970s. Total sample size is 242 (from lateral cephalographs of 124 males and 118 females), with numbers varying by age and measurement. For hard-tissues, boys show clearly defined adolescent spurts, while girls display small velocity increases indicative of only very minor spurts. Forehead tissue thicknesses for both sexes change little and show no demonstrable growth spurts. For the nose and philtrum region, which have the greatest absolute soft-tissue growth changes, both boys and girls show adolescent spurts. Peak velocities are attained between 13 and 14 years in boys and between 11.9 and 12.5 years in girls. Boys appear to have small adolescent spurts for upper (13.7 years) and perhaps lower lip thicknesses. Neither sex displays clear evidence for adolescent spurts in the chin region.

Small for gestational age associated with short stature during adolescence.

This study examined the relationship between intrauterine growth retardation and adolescent stature in a sample of 1510 White subjects (754 males and 756 females) who were evaluated at birth and at the ages of 15, 16, and 17 years. The subjects were classified into two groups based on birthweight, small for gestational age (SGA) and appropriate for gestational age (AGA), corresponding respectively to values below the 10th, and between the 11th and 99th, percentiles of gestational age and sex. Results showed that boys and girls born prematurely (gestational age < 37 weeks of gestation) attained the same stature as those born at full term (>37 weeks of gestation). In contrast, those born SGA were significantly shorter than their counterparts born AGA. The average reduction in stature was 4.9 cm for males and 2.9 cm for females. When the analysis included adjustments for parental stature (and adolescent's age at menarche for females), the average reduction in stature equaled about 3.5 cm for males and 2.0 cm for females. It is thus concluded that the stature deficit reflects a reduction in growth rate rather than delay in maturation. © 1994 Wiley-Liss, Inc.

Reduction in birth weight associated with smoking among young and older-age women.

This study examined the combined effects of maternal smoking and maternal age on birth weight. A sample of 1,851 white, full-term infants (37 to 42 weeks) born to primiparous mothers ranging in age from 18 to 41 years was derived from the database of the Child Health and Development Studies (CHDS), available through the National Technical Information Service (NTIS) of the U.S. Department of Commerce. The mothers were classified into three age groups-young, middle-aged, and older-aged-corresponding respectively to values below the 15th, between the 15th and 85th, and at or above the 85th percentile of age. Analyses of the data show that the reduction in birth weight associated with maternal smoking when compared with nonsmoking averaged 181 gm for the young group (18 to 20 years), 162 gm for the middle-aged group (21 to 29 years), and 154 gm for the older-aged group (30 to 41 years). These differences are independent of total income. Hence it appears that the birth weight-reducing effect of smoking is not enhanced among women of older reproductive ages (30 to 41 years). Furthermore, the reduction in birth weight is dose responsive. That is, the greater the number of cigarettes smoked per day, the lower is the resulting mean birth weight and the higher is the proportion of low-birth-weight infants.