After reviewing the photographic and video evidence over the course of several months, it is clear that “Lucy I” (Subject A/B) and “Lucy II” (Subject C/D) are not the same individual. Several anatomical facts support this conclusion particularly when the profiles are compared.
Retrognathic vs. Prognathic Profiles
Lucy I’s mouth/teeth tend to extend anteriorly (forward). In other words, her mouth area sticks out relative to her other facial structures. This is an underlying feature of Lucy I’s skeletal structure. This skeletal structure would not significantly change if all of her teeth were extracted and dentures worn. In contrast, Lucy II’s profile presents a nearly opposite condition: a prognathic profile with a concave appearance.
Lucy II presents maxilla (upper jaw) retrusion and mandibular protrusion. This protrusion is observable as Lucy II’s mandible/chin is nearly parallel to the tip of her nose, a spot anterior to her nostrile. Yet, Lucy I’s chin is recessed relative to the tip of her nose. The most anterior part of Lucy I’s chin is vertically aligned to a spot posterior to her nostril.
Tooth Extraction and Dentures
Skeletal structure would not significantly change if all of her teeth were extracted and dentures worn.
Dentures, which seem to be at least reasonably well-fit, further support the conclusion that these images depict two different people. The presence of dentures would work to maintain the vertical dimension and prevent over-rotation of the mandible. With the vertical height maintained, there is no good explanation regarding Lucy II’s significant chin protrusion forward when compared to Lucy I.
In addition, Lucy II’s facial height does not appear radically different than Lucy I which, again, supports the opinion that removal of all the teeth is unable to account for the marked change in profiles, particularly the mandibular protrusion.
A Skeletal, Not Dental, Difference
A severly prognathic chin is skeletal, not dental in origin.
Conclusion
During the course of my career, I have performed hundreds of jaw osteotomies (precisely planned fractures of the jaw to reposition the bones) and extracted thousands of teeth. I am familiar with expected changes to an individual’s face as a result of tooth extraction and placement of dentures. It is my opinion that Lucy I and Lucy II are not and cannot be the same individual. These opinions are offered to a reasonable degree of medical certainty.
