Two interpretations of human evolution: Essentialism and Darwinism
Despite intensive studies of a large number of fossils discovered during the 20th century there is no consensus as to the interpretation of the process of hominin evolution. Some authors see as many as six genera and some 17 species, while others argue for a single lineage from Plio/Pleistocene until today. Such diversity of interpretations of the same facts indicates lack of a uniform theoretical basis underlying studies of human evolution. Debates can be resolved using basic principles of scientific inquiry - parsimony and falsification of null hypotheses. Hypothesis testing is now possible with respect to the evolution of basic hominin characteristics such as brain size, body size and the size of the dentition that have sample sizes of a few hundred individual data points each. These characters display a continuous change with time. Analyses of variance do not falsify the null hypothesis of the existence of only one species at any time - variances around regression lines on time do not differ from the variance observed in the single species of Homo sapiens - distributions of residuals are normal. Thus, splitting of the hominin lineage into coeval species can only be based on descriptive characteristics that are liable to errors of subjective judgment.
Obesity is considered a major epidemic of the 21st century. In developed countries, about 1/3 of adults are obese and another 1/3 overweight according to the oversimplified measure - the Body Mass Index. More precise indicators of adiposity: waist circumference, skinfolds, underwater weighing and absorptiometry indicate similar levels of fatness. Obesity per se does not necessarily lead to pathological states, nor to premature mortality. Recent results of large sample studies indicate that more than 1/3 of people classified as obese by fatness indices are physiologically normal. Others, however, suffer from a number of pathological conditions, common among them being the metabolic syndrome and cardiovascular disease. The classical explanation for increasing obesity is the positive energy balance - too much food intake and too little exercise. It seems, however, that this explanation is too simplistic. In societies, and in families, exposed to overeating and lazy lifestyles, about 1/3 of individuals have normal body mass and low levels of fatness, while others become obese. There is, therefore, individual variation in propensity for obesity. We have identified two specific variables differentiating fatness. People who have large lean trunk frames - large volumes of abdominal cavities and thus large gastrointestinal tracts - put on more subcutaneous fat than those with smaller trunk frames (Henneberg and Ulijaszek 2010). This may be a result of larger volumes of food required for antral extension to release ghrelin, or larger surface area of small intestines for food absorption. The second variable is concentrations of Alanine Transaminase, an enzyme responsible for conversion of an amino acid to a carbon skeleton that can be used in fat synthesis. Our study of 46000 young Swiss males (Henneberg, Rühli, Gruber and Woitek 2011) found consistent correlation between levels of Alanine Transaminase and body weight in groups of normal body mass individuals, overweight individuals and moderately obese individuals. Coupling this finding with the fact that among vegetarians, even those living in North America with overabundance of food and low levels of exercise, obesity and overweight are much less common than among non-vegetarians, we have now hypothesized that the increased obesity of modern affluent societies is a result of consumption of animal protein when energy needs are already covered by carbohydrates and fat consumed concurrently. Until the advent of agriculture, humans relied on consumption of a variety of terrestrial and aquatic animals supplemented by relatively small amounts of plant foods. In this situation our bodies became adapted to use proteins as a source of energy, and became efficient at storing occasional surpluses of amino acids by their deamination and conversion to fats. In the modern diets carbohydrates are abundant and provide, together with fats, energy required by human bodies, proteins after deamination are efficiently converted to fats. When new types of crops are introduced to mass production of cheap foods our bodies may not be able to react correctly to all their contents and some of the ingredients may cause additional fatness. An example of widespread recent introduction of industrially processed soybean products that correlates with prevalence of obesity across countries of the world is discussed
Syphilis in the United States during the 1800s and 1900s had a high prevalence rate causing great concern to health officials. Various measures were taken to control its spread. Mercuric treatments were used up until the introduction of penicillin. The aim of this paper is to determine whether dental abnormalities related to congenital syphilis in individuals who died of syphilis or syphilis-related causes, in the Hamman Todd Osteological Collection, occur and whether mercurial treatment was effective. Hutchinson, Moon and Fournier’s works were analyzed to determine dental abnormalities associated with congenital syphilis and its treatments and used as criteria. Hillson et al. (AJPA,107:25-40) standardized method of description of dental changes was used. In the Hamman Todd Osteological Collection in Cleveland, Ohio, 102 individuals had cause of death recorded in the catalogue as syphilis or lues, and 69 had causes of death relating to syphilis which included paresis (53), aortic insufficiency (15) and pericarditis (1). Thus altogether 171 individuals were studied. Dentition was examined to determine if dental abnormalities associated with congenital syphilis and its treatments were present in individuals not recorded as having congenital syphilis. Crania were examined for any osteological changes. One individual (2266) demonstrated dental malformations possibly related to the congenital disease itself, while three demonstrated dental abnormalities associated with mercuric treatments in childhood (2118, 2263 and 3097). No remarkable bone pathologies were evident on any skull. The use of pre-penicillin treatment of congenital syphilis may have been effective to maintain health into adulthood but not always in eradicating the infection. Effects of mercury on enamel formation and bone changes, need to be considered when making a differential diagnosis of syphilis/congenital syphilis.
Adult volunteers (7 females, 7 males) aged between 19 and 51 years, 7 right-handers and 7 left-handers, were asked to complete re-training writing tasks by using their non-dominant hand over 10 consecutive days. It is possible for adults to learn quickly to write legibly with their non-dominant hand. Left handers have a higher legibility score initially although right-handers improved with training more than left-handers. Individual’s performance was unrelated to age and sex in the small sample studied.
In this paper we analyse the ontogeny of craniofacial growth in Ardipithecus ramidus in the context of its possible social and environmental determinants. We sought to test the hypothesis that this form of early hominin evolved a specific adult craniofacial morphology via heterochronic dissociation of growth trajectories. We suggest the lack of sexual dimorphism in craniofacial morphology provides evidence for a suite of adult behavioral adaptations, and consequently an ontogeny, unlike any other species of extant ape. The lack of sexually dimorphic craniofacial morphology suggests A. ramidus males adopted reproductive strategies that did not require male on male conflict. Male investment in the maternal metabolic budget and/or paternal investment in offspring may have been reproductive strategies adopted by males. Such strategies would account for the absence of innate morphological armoury in males. Consequently, A. ramidus would have most likely had sub-adult periods of socialisation unlike that of any extant ape. We also argue that A.ramidus and chimpanzee craniofacial morphology are apomorphic, each representing a derived condition relative to that of the common ancestor, with A. ramidus developing its orthognatic condition via paedomoporhosis, and chimpanzees evolving increased prognathism via peramorphosis. In contrast we suggest cranial volume and life history trajectories may be synapomorphic traits that both species inherited and retained form a putative common ancestral condition. Our analysis also provides support for the hypothesis that an intensification of maternal care was central to the process of hominization.
Although the concept of race has been thoroughly criticised in biological anthropology, forensic anthropology still uses a number of methods to determine the ‘race’ of a skeleton. The methods must be evaluated to see how effective they are given large individual variation. This study used 20 cases of skeletons of varied provenance to test whether the nine published methods of ‘race’ determination, using a range of various approaches, were able to consistently identify the ethnic origin. No one individual was identified as belonging to just one ‘major racial class’, e.g. European, meaning that complete consistency across all nine methods was not observed. In 14 cases (70%), various methods identified the same individual as belonging to all three racial classes. This suggests that the existing methods for the determination of ‘race’ are compromised. The very concept of ‘race’ is inapplicable to variation that occurs between populations only in small ways and the methods are limited by the geographic population from which their discriminant functions or observations of morphological traits were derived. Methods of multivariate linear discriminant analysis, e.g. CRANID, are supposed to allocate an individual skull to a specific population rather than a ‘major race’. In our analysis CRANID did not produce convincing allocations of individual skeletons to specific populations. The findings of this study show that great caution must be taken when attempting to ascertain the ‘race’ of a skeleton, as the outcome is not only dependent on which skeletal sites are available for assessment, but also the degree to which the unknown skeleton’s population of origin has been investigated.
Ballistics literature often focuses on soft tissue injures and projectile trauma to the cranium. Minimal details on the bony characteristics of projectile trauma to the thorax/abdomen regions have been published. This study aims to analyse projectile trauma to the bony trunk region including the ribs, vertebrae, scapula, sternum and the hip bone to form a better understanding of the characteristics and biomechanics of skeletal trauma caused by a projectile and contribute to the existing database on skeletal trauma caused by projectiles. Fourteen cases of documented projectile trauma to the bony regions of the trunk from the Hamman-Todd Human Osteological Collection at the Cleveland Natural History Museum, Ohio were analysed. Of the 14 individuals with gunshot wounds examined, 40 wounds occurred to the bones. Twenty- four injuries to the ribs, 1 ilium, 11 vertebrae, 3 scapulae, and 1 sternum. Fracture patterns, heaving and bevelling can be used to determine the direction of travel of the projectile which can be evident on the ribs, sternum, scapula and ilium. It is critical to understand the wounding patterns associated with projectile trauma to the torso region as this is often targeted, due to being the centre of mass.
Many theories have been advanced to explain human hairlessness, however, there is no consensus. This study of 76 males observed that skin reflectance measuring skin colouration and melanin pigmentation correlated with hair size and follicle density. Individuals with a greater concentration of melanin within the superficial layer of the skin had a lower follicle density and smaller sizes of hairs. In contrast, individuals with a lower melanin concentration and lighter skin colour had a full range of hairiness. This leads to the suggestion that over the course of human evolution, high concentrations of melanin in consistently exposed to ultraviolet radiation areas developed first and that hair loss was a consequence of competition in the skin between melanin production and hair growth. Darker pigmented skin and lower follicle density are significantly correlated (R2=0.283; p<0.05). Individuals with darker skin had a mean of 4.91 follicles per cm2 whereas those with lighter skin reflectance had 11.20 follicles per cm2. This suggests that increased concentrations of melanin in the basal layer of the epidermis may limit hairiness by negatively influencing the skin's ability to produce hair.
South Africa underwent major social and economic change between 1987 and 1995. The release of Nelson Mandela in February 1990 proclaimed an end to the political system of apartheid, and the first freely elected non-White government in 1994 instigated social and economic reforms aimed at alleviating the consequences of apartheid. This paper aims to examine the impact of these socio-economic and political changes on height, weight and body mass index (BMI) in childhood and late adolescence. An analysis was carried out of longitudinal data of 258 urban and rural South African Cape Coloured schoolchildren (6-18 years old) across the transitional periods from apartheid between 1987 and 1990, to this transition between 1991 and 1993, and finally to post-apartheid between 1994 and 1995. The anthropometric measures were standardized into age independent Z-scores. Analyses of variance with repeated measures were conducted to examine the growth in height, weight and BMI across these periods. The results show a significant main effect of measurement periods on height, weight and BMI Z-scores. Across time, the subjects increased in overall size, height, weight and BMI. For all the anthropometric measures there was a significant interaction effect between measurement period and sex, but none between measurement period and SES. The average increase in height, weight and BMI across time differed significantly for girls and boys, the average z-scores being greater in girls than in boys. For boys, there was little difference in height, weight and BMI Z-scores according to SES, and little increase across periods. Girls were generally taller, heavier with greater BMI than boys, and their scores increased across the time periods. High SES girls were taller, heavier and had higher BMI than low SES girls. Across the measurement periods, BMI and weight somewhat converged between the high and low SES girls. In the discussion these differences reflecting social sex distinctions are addressed.
Palmistry or Chiromancy is the art of reading lines on the palm of the hands. Today, many researchers believe that the lines on the palms of the hands can predict the individual’s future. Computer programs are being designed which can automatically read the lines on the palm of the hand. One popular theory is that the length of the line of life will indicate lifespan. This theory was investigated in 1974 by Wilson and Mather who found no significant correlation between life expectancy and the length of the line of life. In 1990 Newrick and colleagues found a significant correlation as measured on 100 cadavers. These conflicting investigations are the only existing studies which have explored the relationship between palmistry and longevity. Since then no other study has validated nor disproven these claims.
A total of 60 cadavers donated to The University of Adelaide were used in this study. Total hand length and the line of life length were measured on all cadavers. The age at and cause of death were also recorded. Linear regressions were used to establish any correlations between longevity and the length of the line of life. No significant correlations were found. There was also no significant difference between males and females or the right or left hands.
As no significant correlations were found between longevity and the line of life all efforts at producing more reliable and automatic ways to read the lines are futile. This study puts to rest any debate surrounding the use of the line of life in palmistry as introduced by Newrick and colleagues.