The rootless hair and differing mitochondrial DNA in two hair shafts taken from the same body.

The hair used by Colleen Fitzpatrick to assist in identifying the Somerton Man had no root, given that, another method of identifying the body would be by morphological analysis – which is achieved by using using two hairs taken from the same body. This wasn’t done in the SM case as Fitzpatrick only had one hair available.

Morphological analysis of hair is a forensic and scientific examination of the hair shaft’s cuticle, cortex, and medulla to determine species (human vs. animal), body area, and potential donor characteristics. Using light microscopy, analysts check features like scale patterns (imbricate in humans), pigmentation, and medullary index to provide class evidence, which can be strengthened if a root is present for DNA. 

However, it is entirely possible for two hairs taken from the same body – or even the same head – to exhibit significant morphological differences and not share identical characteristics, in other words, his genetic profile.

While hair from a single individual generally shares a common genetic profile, microscopic characteristics such as diameter, pigment distribution, and medulla structure can vary.

In the Somerton Man case, Abbott and Colleen Fitzpatrick, a renowned genealogist who founded Identifinders International, used new DNA technology that allows more thorough testing of rootless hair to obtain the unknown man’s genetic profile. They then used that genetic profile to build the man’s family tree and narrow down his possible identity.

Now we can talk about heteroplasmy.

Mitochondrial DNA in hair shafts can differ significantly between two hairs taken from the same person—or even along the same single hair. 

This occurs due to a phenomenon known as heteroplasmy. 

• Heteroplasmy: An individual can have a mixture of different mtDNA sequence types within their body, rather than just one.
• Hair-Specific Variation: Hair follicles can display higher levels of heteroplasmy than other tissues like blood or cheek cells.
• Bottleneck Effect: The development of separate hair follicles involves a “somatic bottleneck,” where only a limited number of mtDNA molecules are passed on, leading to different hairs containing different proportions of mutant and normal mtDNA.
• Forensic Implications: Because of this variability, forensic scientists must interpret hair mtDNA results carefully, as two hairs from the same suspect might show differences, whereas in other tissues (like blood) they would be identical. 
  While a single, inherited maternal sequence is the rule, heteroplasmy and the independent development of hair follicles can lead to different genetic markers in different hairs. 

Some of the above may need confirmation by the appropriately qualified personnel..

This is where the inspiration for the post came from.