The bones in our body give modern humans a gracile appearance with what is known as a low trabecular density. All of our ancestors, whether hominins or the great apes, generally had much heavier bones and therefore presented a quite different aspect within their habitats. Apart from the canopy-living gibbons, they had an enlarged body size that gave them massive limbs until the modern hominins of the Holocene, a mere 12 thousand years ago.

The reasons for this startling difference may lie in our more sedentary agricultural life-style and reliance on cultural items to aid us in our endeavours, Habiba Chirchir and her X colleagues from George Washington University, in DC, and many prestigious institutions in Europe and the US present their findings in PNAS as Recent origin of low trabecular bone density in modern humans.

The research for this paper involved very high resolution imaging of the joints from fossil limbs. The results show dramatic decrease in the trabecular density, even among some recent humans. They prove that especially in the lower limbs, we were more suited to farming than our original hunter/gatherer or foraging niche. Our relatives, the chimpanzees have a less enlarged body size but much greater bone density. Sorting thought the relatives, from Austalopithecus africanus and Paranthropus robustus, to Homo neanderthalensis and early Homo sapiens resembling our skeleton to some extent, only the most recent have hips, knees and ankles vastly reduced in density , along with the shoulder, elbow and hand to a lesser extent.

Sufferers from osteoporosis will not be so gratified to learn that because we walk less now, the condition has become typical of modern populations. The change in lifestyle has reduced the bones' strength and lifestyle is probably quite important to prevent some inherited complaints such as this. We appear to be designed to walk and run on the African plain, but each new habitat and niche our populations adopted gave us different appearances. One thing stands out: that most races and shapes of human are agricultural by habit and are gracile in form because of this and related factors. Perhaps the hobbit form on Flores (Indonesia) can now be explained better by looking at their enormous feet!