A new study of fossils has revealed that the human body has gone through four main stages of evolution.
Researcher Rolf Quam of the Binghamton University and colleagues studied the body size and shape in the human fossil collection from the site of the Sima de los Huesos in the Sierra de Atapuerca in Northern Spain.
The researchers found that the Atapuerca individuals were relatively tall, with wide, muscular bodies and less brain mass relative to body mass compared to the Neanderthals.
The Atapuerca humans shared many anatomical features with the later Neanderthals not present in modern humans, and the analysis of their postcranial skeletons indicated that they were closely related evolutionarily to the Neanderthals.
Quam said that this was really interesting since it suggested that the evolutionary process in their genus was largely characterised by stasis in the body form for most of our evolutionary history.
The comparison of the Atapuerca fossils with the rest of the human fossil record suggested that the evolution of the human body has gone through four main stages, depending on the degree of arboreality (living in the trees) and bipedalism (walking on two legs). The fossils represent the third stage, with tall, wide and robust bodies and an exclusively terrestrial bipedalism, with no evidence of arboreal behaviors.
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The authors suggested that the Atapuerca humans offer the best look at the general human body shape and size during the last million years before the advent of modern humans.
The study has been published in the Journal Proceedings of the National Academy of Sciences.