Recent origin of low trabecular bone density in modern humans

Habiba Chirchir, Tracy L. Kivell, Christopher B. Ruff, Jean Jacques Hublin, Kristian J. Carlson, Bernhard Zipfel, Brian G. Richmond

Research output: Contribution to journalArticle

Abstract

Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/ early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

Original languageEnglish (US)
Pages (from-to)366-371
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number2
DOIs
StatePublished - Jan 13 2015

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Keywords

  • Gracilization
  • Homo sapiens
  • Human evolution
  • Sedentism
  • Trabecular bone

ASJC Scopus subject areas

  • General

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