Slow, Progressive Transition From the Trees, Embrace of Tools Conjectured for Hominin Evolution

Fossil hominin shoulders support an African ape-like last common ancestor of humans and chimpanzees

Authors:

Young et al

Abstract:

Reconstructing the behavioral shifts that drove hominin evolution requires knowledge of the timing, magnitude, and direction of anatomical changes over the past ∼6–7 million years. These reconstructions depend on assumptions regarding the morphotype of the Homo–Pan last common ancestor (LCA). However, there is little consensus for the LCA, with proposed models ranging from African ape to orangutan or generalized Miocene ape-like. The ancestral state of the shoulder is of particular interest because it is functionally associated with important behavioral shifts in hominins, such as reduced arboreality, high-speed throwing, and tool use. However, previous morphometric analyses of both living and fossil taxa have yielded contradictory results. Here, we generated a 3D morphospace of ape and human scapular shape to plot evolutionary trajectories, predict ancestral morphologies, and directly test alternative evolutionary hypotheses using the hominin fossil evidence. We show that the most parsimonious model for the evolution of hominin shoulder shape starts with an African ape-like ancestral state. We propose that the shoulder evolved gradually along a single morphocline, achieving modern human-like configuration and function within the genus Homo. These data are consistent with a slow, progressive loss of arboreality and increased tool use throughout human evolution.

Tejas LCA Mark I Declared "Operationally Deficient"

India's Comptroller and Auditor General (CAG) declared on 8 May that the locally designed Tejas Light Combat Aircraft (LCA) Mk I was "operationally deficient" and its pilots vulnerable even to 7.62 mm rounds fired at the fighter's front end.

In the 63-page report tabled in parliament, Shashi Kant Sharma revealed that the long-delayed LCA Mk I, which obtained its second initial operational clearance (IOC-2) in December 2013, had failed to meet the Indian Air Force's (IAF's) air staff requirements on numerous counts.

It disclosed that to secure IOC-2, the LCA Mk I - under development by the state-run Aeronautical Development Agency (ADA) since 1983 - had to be granted 53 waivers, of which 20 were permanent.

The latter would remain, the CAG said, even after the platform secured its final operational clearance (FOC) scheduled for December 2015. IAF sources said FOC was likely to be deferred.

The LCA Mk I obtained its first IOC from the Centre for Military Airworthiness and Certification in Bangalore in January 2011, only for it to be re-confirmed in 2013 by the definitive IOC-2.

The persistent shortcomings, some of which were still under design, development, and testing, include excessive weight, engine thrust, reduced internal fuel capacity, non-compliance of all-weather operations, non-achievement of single-point defueling fuel system protection, and pilot protection. They restrict the "operational efficiency and survivability of the aircraft, thereby limiting its employability when inducted into IAF squadrons", the report said.

It is also "deficient in electronic warfare (EW) capabilities as specified by the IAF, as the self-protection jammer could not be fitted on the aircraft due to space constraints", the report stated.

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India's Naval LCA Variant Does First Ski Jump Test

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