Well based on the papers out there it's based on regression algorithms and population data and jaw bone variations along with skull featuresUhh, not to interrupt , but is an anthropologist saying "hey, we should stop using phrenology" a good thing? You know, because phrenology is bullshit?
Uncloaking a Lost Cause: Decolonizing ancestry estimation in the United States
Special Issue: Race reconciled II: Interpreting and communicating biological variation and race in 2021 Confederate monument in Bedford County, VA used as an analogy for the use of a similarly racist...onlinelibrary.wiley.com
Determination of Race from the Skeleton through Forensic Anthropological Methods - PubMed
Metric and morphological techniques employed by forensic anthropologists for determination of race are reviewed. Included are several studies which examine cranial morphological techniques such as presence of the oval window of the inner ear, which occurs more frequently in Whites than in Native...
pubmed.ncbi.nlm.nih.gov
You could probably also throw in mineral analysis as some areas minerals end up in the bones.