The below study suggests that growth is manituable not only be nutrition but also by mechanical loading(tool use). It states that growth of some elements of the body is prioritized over others in times of nutrient restriction(“the thrity phenotype” hypothesis). Although this study is more geared to that nutrition can alter body height and skeletal length growth. Proving the plasticity(ability of bone to change in length) of bone is essential in proving that bone can change in response to mechanical loading.

Plasticity in the growth of body segments in relation to height-for-age and maternal education in Guatemala

“Plasticity in the growth of body segments between populations has been researched in relation to migration, temporal change and high-altitude studies{height seekers could potentially manipulate altitude or temperature}. We study the within population variation in body segments, thus controlling for some of the environmental and genetic differences that could be at play in between populations studies. We test a version of the thrifty phenotype hypothesis, where the growth of head-trunk and hand are prioritized due to their functional significance over height and leg growth.

A total of 3913 Guatemalan, rural, semi-urban and urban, Maya and Ladino children 6 to 15 years old were studied. Height, sitting height, leg length, and metacarpal length were studied in relation to three proxies for living conditions: height- and leg length-for-age, and maternal education. Estimation statistics and null hypothesis significance testing were used to analyze the data.

Metatarsal length and sitting height values were higher than height and leg length respectively. Relative metacarpal length was conserved across height-for-age groups. Females were less affected than males for metacarpal length and sitting height, but more affected for leg length.

Our results agree with the thrifty phenotype hypothesis, where metacarpal and sitting height growth would be prioritized over height and leg length due to greater functional significance.“

“Plasticity refers to the ability of an organism to modify its biology to respond to changes in the environment, particularly when these changes are physiologically stressful”<-plasticity in height is a very promising idea for height as it means height and bone length can be manipulated.

“in conditions of environmental stress, leg length is often more sensitive than is the head-trunk segment, and that tibia and ulna lengths are also more sensitive than humerus, hand and foot lengths. A proximate reason for this sensitivity is due to the allometry of skeletal growth, where the more proximal body segments grow fastest prenatally and are less exposed to extra-uterine environmental stress, but more distal segments grow most rapidly after birth and are more exposed to environmental stress. The thrifty phenotype hypothesis offers an ultimate evolutionary explanation; the growth of human body segments with greater functional significance, such as “head-brain,” “trunk-major organs,” and “hands-tools” will be prioritized over forearms and legs.”

“the thrifty phenotype hypothesis over the predictions of the distal blood flow and cold adaptation models in the growth of different body segments in living populations “

“According to this hypothesis, the growth of the head-trunk segment would be prioritized due to the important organs that it houses (brain, heart, lungs), and the growth of the hand would be prioritized due to its manipulative function in human tool technology, thus offering an ultimate evolutionary explanation for the differential plasticity in the growth of body segments under different conditions of stress.”

the thrifty phenotype hypothesis is basically that growth is conserved based on nutrients with some bones being prioritized over others in times of nutrient restriction.