Agriculture Reference
In-Depth Information
close to the center (Ruff 2000). Physical anthropologists have modified the engineer-
ing measurements for the study of strength of limb bones in ancient skeletons. In
fact, over the course of human evolution and especially since agriculture first began,
there has been a reduction in bone size and bone strength (Larsen 1997). These find-
ings strongly suggest that the foraging-to-farming transition resulted in a decline in
workload. This finding is consistent with a reduction in osteoarthritis, a disorder of
the joints of the skeleton resulting from excessive wear and tear owing to lifestyle
and physical activity.
the chAngIng fAce of humAnIty
One of the biggest misconceptions about the evolution of recent humans, say within
the last 20,000 years or so, is that once humans became anatomically modern, their
evolution came to an end. There is a growing body of evidence based on the study of
skulls dating to the last 20,000 years, and especially the last 10,000 years, that there
has been continued morphological change in the human cranium. One of the first
to observe this was the eminent British anatomist and physical anthropologist, Sir
Arthur Keith (1916). Using skulls from the last several thousand years in Britain, he
documented a reduction in the size of the face and jaws, which he related to eating
soft foods, especially cooked cereal grains. That is, following what is now known as
Wolff's law, by which bone is placed where it is needed and taken away where it is
not, facial bones are reduced in size.
Since the early nineteenth century, many other anthropologists have documented
a reduction in the robusticity of the faces and jaws globally (e.g., Carlson and Van
Gerven 1979, Larsen 1982, Walimbe and Tavares 2002, and others). Moreover, these
changes are often accompanied by a general shortening and rounding of the skull.
Physical anthropologists David Carlson and Dennis Van Gerven (1979) developed
their
masticatory-functional hypothesis
to explain these changes. They offered that
the change in skull shape and gracilization of the face and jaws was a response to
decreased demands placed on the chewing muscles (temporalis and masseter) as
people shifted from eating hard foods (nondomesticated plants) to soft foods (domes-
ticated plants). Importantly, the shift to eating domesticated plants was also accom-
panied by the invention of ceramics, used for cooking food into soft mushes. There
is now an abundant body of experimental research on laboratory animals to support
their hypothesis. In control studies comparing animals fed hard-textured foods with
others fed soft-textured foods, the ones with the harder diets had bigger jaws and
faces than the ones with softer diets (e.g., Ciochon et al. 1997 and many others).
Clearly, bone is responsive to the mechanical environment, including bone tissue
associated with chewing.
The reduction in the size of the jaws has also had an impact on our teeth. One
question I ask my anthropology classes is how many had to have orthodontic treat-
ment (“braces”) when they were children. In every instance, at least half of the stu-
dents answer in the affirmative. This informal polling represents a cross section of
the public and reflects the fact that malocclusions and malaligned teeth and jaws
affect a huge portion of our population. Yet, when I look at ancient skulls, malocclu-
sions, crooked and crowded teeth (the so-called wisdom teeth are a great example),
