The femoral neck-shaft angle (NSA) varies among modern humans but measurement problems and sampling limitations have precluded the identification of factors contributing to its variation at the population level. Potential sources of variation include sex, age, side (left or right), regional differences in body shape due to climatic adaptation, and the effects of habitual activity patterns (e.g. mobile and sedentary lifestyles and foraging, agricultural, and urban economies). In this study we addressed these issues, using consistent methods to assemble a global NSA database comprising over 8000 femora representing 100 human groups. Results from the analyses show an average NSA for modern humans of 127°(markedly lower than the accepted value of 135°); there is no sex difference, no age-related change in adults, but possibly a small lateral difference which could be due to right leg dominance. Climatic trends consistent with principles based on Bergmann's rule are evident at the global and continental levels, with the NSA varying in relation to other body shape indices: median NSA, for instance, is higher in warmer regions, notably in the Pacific (130°), whereas lower values (associated with a more stocky body build) are found in regions where ancestral populations were exposed to colder conditions, in Europe (126°) and the Americas (125°). There is a modest trend towards increasing NSA with the economic transitions from forager to agricultural and urban lifestyles and, to a lesser extent, from a mobile to a sedentary existence. However, the main trend associated with these transitions is a progressive narrowing in the range of variation in the NSA, which may be attributable to thermal insulation provided by improved cultural buffering from climate, particularly clothing.

This paper presents a thermal model for the prehistoric origin and development of clothing. A distinction is drawn between simple and complex forms of clothing, with broad implications for the interpretation of paleolithic technological transitions and the emergence of modern human behavior. Physiological principles and paleoenvironmental data are harnessed to identify conditions requiring simple, loosely draped garments and the more challenging conditions that demanded additional protection in the form of complex garment assemblages. No actual clothing survives from the Pleistocene, yet the archaeological record yields evidence for technological and other correlates of clothing-more evidence than is generally supposed. Major innovations and trends in the distributions and relative frequencies of lithic and other tool forms may reflect the changing need for portable insulation in the context of fluctuating ice age climates. Moreover, the nonthermal repercussions of complex clothing can be connected with archaeological signatures of modern human behavior, notably adornment. Alternative models are less parsimonious in accounting for the geographical and temporal variability of prominent technological and other behavioral patterns in association with environmental change.

No abstract

Thermal considerations can help resolve two of the most challenging problems in later Palaeolithic archaeology-the demise of Neanderthals and the emergence of modern human behaviour. Both can be viewed as reflecting interactions between biological and behavioural cold adaptations, in the context of extreme climatic fluctuations during the Upper Pleistocene. Recent studies draw attention to the special difficulties these conditions posed for humans but few give sufficient regard to the need for adequate pre-adaptations, namely technologies for manufacturing complex clothing assemblages. It is argued here that pre-existing biological cold adaptations delayed the development of such technological capacities among Neanderthals, resulting ultimately in their extinction. In contrast, the greater biological vulnerability of fully modern humans promoted a precocious appearance of behavioural adaptations among some (though not all) groups, visible in the various archaeological markers of modern human behaviour.

CLIMATE CHANGE AND THE INVENTION OF CLOTHES T he human need for clothes did not start out from any sense of modesty nor a desire to decorate ourselves: naked hunter-gatherers, such as the Australian Aborigines, can easily disprove those theories. This is likewise for theories of clothing origins that are based on social purposes, such as displaying social roles. Of course, these motivesmodesty and displayare often the main reason why we wear clothes in the modern world. And, like a lot of modern things, they are rather contradictory: we like to show ourselves, and we also like to cover ourselves. Clothes embody these ambivalent feelings about our bodies. Display and modesty make more sense as later motives: they arose as reasons to wear clothes once we had already adopted clothing. And yet, these were the motives that finally made clothes indispensable and permanent. The psychosocial need for clothes played a big role in our modern developmentin the emergence of agriculture, for example, as we shall see. So, we should not discount the roles of modesty and display, but in searching for original causes, we have a couple of more respectable candidates. First, is our biological nakedness: we lack natural body cover in the form of fur. As mentioned in the first chapter, this is an unusual trait for any mammal, though not unique: some other species also became naked. And it is true that our own nakedness varies quite markedly and is never complete: we still retain some body hairsome people more than othersbut we are nonetheless naked in a biological sense. In a moment, we shall look at the questions of when and why our hominin ancestors lost their fur cover.