Whoops! Australopithecus afarensis Lucy's Backbone Isn't Hers, Really a Baboon's!

Lucy's back: Reassessment of fossils associated with the A.L. 288-1 vertebral column

Authors:

Meyer et al

Abstract:

The Australopithecus afarensis partial skeleton A.L. 288-1, popularly known as “Lucy” is associated with nine vertebrae. The vertebrae were given provisional level assignments to locations within the vertebral column by their discoverers and later workers. The continuity of the thoracic series differs in these assessments, which has implications for functional interpretations and comparative studies with other fossil hominins. Johanson and colleagues described one vertebral element (A.L. 288-1am) as uniquely worn amongst the A.L. 288-1 fossil assemblage, a condition unobservable on casts of the fossils. Here, we reassess the species attribution and serial position of this vertebral fragment and other vertebrae in the A.L. 288-1 series. When compared to the other vertebrae, A.L. 288-1am falls well below the expected size within a given spinal column. Furthermore, we demonstrate this vertebra exhibits non-metric characters absent in hominoids but common in large-bodied papionins. Quantitative analyses situate this vertebra within the genus Theropithecus, which today is solely represented by the gelada baboon but was the most abundant cercopithecoid in the KH-1s deposit at Hadar where Lucy was discovered. Our additional analyses confirm that the remainder of the A.L. 288-1 vertebral material belongs to A. afarensis, and we provide new level assignments for some of the other vertebrae, resulting in a continuous articular series of thoracic vertebrae, from T6 to T11. This work does not refute previous work on Lucy or its importance for human evolution, but rather highlights the importance of studying original fossils, as well as the efficacy of the scientific method.

Complicating Human Evolution: Is Little Foot as old as Lucy?

New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan

Authors:

Granger et al

Abstract:

The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 (‘Little Foot’) in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling. Much of the existing chronology based on uranium–lead dating and palaeomagnetic stratigraphy has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence Earlier dating with cosmogenic nuclides suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking . Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 ± 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it. The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa. We also date the earliest stone tools at Sterkfontein to 2.18 ± 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans and Wonderwerk.

This would have gone up yesterday, but April 1st...