Tracing the Human Lineage
The Ontogeny - Phylogeny Calcaneal Model
This supposition is based on my clinical research which entailed the discovery of a previously unrecognized inherited foot structure, the PreClinical Clubfoot Deformity (Structure). The hallmark of this foot structure is the structural twist (supinatus) in the posterior aspect of the calcaneus. This is the same structural twist found in the fossilized calcaneus of the A.sebida but lacking in the A.africanus. From this the OPCM would conclude that A.sebida is a direct descendant of H.sapien, A.africanus is not.
The PreClinical Foot Structure appears to be at least 2 million years ago and possibly older.
In 2014, the most common foot structure is the PreClinical Clubfoot Structure/Deformity.
The least common is the Plantargrade Foot Structure (heel bone no longer retains any supinatus/structural twist).
I opine that the homo sapien foot is still very early in its anthropological evolution, evolving towards the very stable bipedal plantargrade foot structure.
All Comments are Welcomed!
It has become progressively apparent that the H.sapien has emerged from a rather bushy phylogeny, where there once was a diverse and divergent group of hominin species.
Teasing out the precise relatedness of these hominin fossils to one another has proved to be a daunting enterprise. The sheer diversity of the fossilized remains has complicated our understanding of H.sapien's evolution.
For example, it appears that A.ramidus was a direct descendent of H.sapiens. However determining whether A. afarensis of A. africanus (both habiltating the earth during the same epoch) were direct descendants or not, has proved more difficult to determine.
Photo of the foot fossil of A.sediba
Courtesy of DeSilva JM et al 2013. The Lower Limb and Mechanics of Walking in Australopithecus sediba. Science 340, DOI: 10.1126/science. 1232999
There is an overall consensus of opinion that H.sapien lineage has passed through ardipithecine to australopithecine, and on to the transitional hominins, pre-modern and finally modern Homo. But exactly which hominins comprise this direct lineage to Homo, has been the holy grail.
The Ontogeny - Phylogeny Calcaneal Model (OPCM) (as proposed by Dr Rothbart)
The OPCM provides a concise and straight forward roadmap in deciphering the Hominin lineage.
Calcaneal supinatus (twist pattern in the posterior aspect of the heel bone) is the marker in determining whether or not the fossilized heel bone comes from a direct descendant of h.sapiens, or not (See Photo below of structurally inverted calcaneus).
The above comments were extrapolated from a discussion on the evolution of Homo Sapien - www.Researchgate.net December 18, 2014