A comparative anatomical study of lumbar skeletal elements: evolutionary implications for bipedal locomotion

• Published in: The FASEB journal 2006-03, Vol.20 (4), p.A444-A444
• Main Authors: Harwayne‐Gidansky, Ilana, Sarmiento, Esteban E, Tuttle, Russell H, Marquez, Samuel
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.20.4.A444-c

Plio‐pliestocene fossil hominoids are assumed to be bipeds ‐ a hallmark characteristic for the Family rank of Hominidae. This assumption is based on some postcranial anatomical similarities to Homo sapiens that are considered in the literature to be diagnostic of bipedality. One such feature is lumbar lordosis. Despite not one fossil presenting a complete lumbar and sacral column to affirm this characteristic, its assumed presence has been used to argue these fossils as bipeds, and thus Hominidae. This study measured lumbar vertebral body wedging in a number of extant anthropoids, human cadaveric dissections, and fossil hominoids from museum collections and medical school material. Results showed that positive vertebral body wedging is associated with a marked human‐like lumbar lordosis. Slight lordosis as documented for baboons, was not associated with positive vertebral body wedging. For corresponding vertebral bodies, the wedging value of the L3 vertebral body of AL 288‐1 (Praeanthropis africanus‐ “Lucy”) falls midway between those of female humans and chimpanzees. Published data shows AL‐288‐1 to have a high sacral promontory angle suggesting that this specimen may have lacked a lumbar lordosis, and thus would not have been a habitual biped. This study corroborates the sacral evidence in suggesting the absence of a lumbar lordosis for AL 288‐1, and concludes that this specimen was probably not a committed biped thus rendering its taxonomic status as a hominid less certain.