Chris Ruff and colleagues (2005) provide additional statistics on body mass in high latitude populations, including Inupiat and Finns. The importance of the paper is that previous regressions to estimate body mass in fossil humans have been based on lower-latitude populations. High latitude populations with broader pelves might be expected to have a slightly different mass than would be predicted for lower latitude populations, so adding the new samples ought to improve accuracy of estimation. Ruff and colleagues found that the new samples did result in slightly higher estimates of body mass for fossil Neandertals and other high latitude samples (including earlier and later Europeans and the Jinniushan skeleton from northern China). These estimates were not very far from the original estimates based on the earlier comparative sample, though, so the effect is minor.
Whenever I see estimates like these, they serve as a reality check of sorts about the common knowledge that Neandertals were massive and stocky in body form. The new body mass estimates for Neandertals are 75.8 kg (166 lb) for La Chapelle-aux-Saints and 82.3 kg (181 lb) for Kebara. When I was in high school, I was pretty lean myself and I wrestled in the 185 pound weight class. In other words, these massive Neandertals were nothing like the people we consider to be massive today.
On the other hand, they were hunter-gatherers, so we are in a whole different world in terms of fatness. Ethnographic hunter-gatherers are relatively small in terms of both mass and stature. But then, ethnographic hunter-gatherers tend to live in relatively marginal environments with more or less severe scarcity of resources. To give a bit of scale, Katzmarzyk and Leonard (1998) report on body mass in populations with different mean temperature. The sample is not huge, but it is illustrative:
The red line on the chart I inserted at the body mass of La Chapelle. It is slightly large for an Eskimo, and slightly larger for an African (although notably not for a Polynesian). The important point is that the Neandertals were really not all that large compared to today's humans, whether we look at industrialized societies or not. If we accept the large size of a few specimens as indications of a large average mass in the population, this population is still not striking. Ruff (2002) provides a good review of the variation in body size in recent and living human populations. Considering the evidence that human body size has decreased over the terminal Pleistocene and Holocene, Neandertals would appear to be even closer to us and to contemporary populations.
Neandertals mainly appear to stand apart because of the contrast between them and later Europeans. This contrast mainly stems from the taller stature of later people, but in addition to an increase in height there was also a reduction in pelvic breadth. Overall, this appears to indicate a smaller mass for Upper Paleolithic Europeans, although the sample of individuals with both stature and bi-iliac measurements is very small (n = 6 in Ruff et al. 2005).
Ruff (2002:217) presents the following hypothesis:
One possible explanation for these observations is that the Late Pleistocene reduction in body size was due primarily to genetic factors, possibly reduced selection for large body size in association with technological improvements (Frayer 1984), whereas the succeeding fluctuations (decrease, then, in higher latitudes, increase) in body size in the Holocene were due to environmental effects on growth, e.g., nutrition.
The first part of this hypothesis begs for testing. An alternative is that the dietary changes that led to nutritional deficits in growing people were established long before the Holocene when agricultural subsistence patterns appeared. With their constant technological improvements, Upper Paleolithic people appear to be working much harder for their subsistence than Neandertals. Or social stratification may have led to inequities in food access that likewise had developmental consequences. One might even imagine that delayed maturation was an adaptation to restriction in calories or micronutrients during development -- which might make sense considering that undernourished populations today exhibit slower developmental times and delayed maturation compared to Westernized populations.
Of course if there was no mass reduction in Upper Paleolithic people, the first part of the hypothesis is moot.
As a bottom line, Neandertals were pretty clearly distinctive in their body proportions, by having broad pelves, short distal limb segments, and relatively short statures. But this distinctiveness did not necessarily extend to greater body mass, especially in comparison to contemporary and earlier humans, and present-day Europeans. If you have an image of Neandertals as hulking, muscle-bound brutes (or hulking, muscle-bound hunks, depending on your taste), then please consider that in Olympic boxing terms, La Chapelle's mass of 75.8 kg is just above the border between middleweight and light heavyweight, two classes below the maximum. The real heavyweights (i.e. super heavyweight class) start at full 14 stone, or 91.6 kg. That includes the pelvis from Atapuerca, but so far no other fossil humans.
Katzmarzyk PT and Leonard WR. 1998. Climatic influences on human body size and proportions: Ecological adaptations and secular trends. Am J Phys Anthropol 106:483-503. Wiley InterScience
Ruff C. 2002. Variation in human body size and shape. Ann Rev Anthropol 31:211-232. Annual Reviews
Ruff C, Niskanen M, Junno J-A, Jamison P. 2005. Body mass prediction from stature and bi-iliac breadth in two high latitude populations, with application to earlier higher latitude humans. J Hum Evol 48:381-392.