206 bones in your body? Or do YOU have 208?: possible evolutionary change in human anatomy.

As the "shin bone is connected to the knee bone" our knees may have an extra inconspicuous addition called the fabella, which has been seen to be nearly 3.5X more common 

than 100 years ago. The fabella is a name which is  Latin for ‘little bean’. The fabella is a sesamoid bone located behind the lateral femoral condyle in the lateral head of the gastrocnemius, or in layman's terms in the back of the knee attached to the femur that can grow in your lifetime. However, this is not the first time we've seen the fabella appear, for it's very common in non-humanoid mammals. A range of genetic and environmental explanations have been proposed to explain this variation, but few studies consider more than one population for statistical analyses. Therefore a study that did consider this was published in the Journal of Anatomy (2019) that performed a worldwide meta-analysis of fabella prevalence rates to address the following questions:

1. Are there sexually dimorphic differences in fabella prevalence rates?

2. How do prevalence rates change with ontogeny?

3. Are bilateral or unilateral cases more common? Among unilateral cases, are fabellae more common in right or left knees?

4. What is the global prevalence rate of the fabella? How do these rates vary in different regions of the world?

After various statistical analyses, dissections, and medical approved 'big data' collection the following results were concluded; 
1. That Prevalence rates increase with time, and are higher for dissection‐based studies than for X‐ray‐based ones( dissection‐based studies include some cartilaginous/less dense, ossified fabellae). 
2.The median frequency of unilateral and bilateral cases is 27.0% and 72.94%, respectively. Fabellae showed no significance (P = 0.9992) in unilateral cases between which knee it is found in. 
3. in the  22 studies from 1875 to 2018 containing sex‐specific data, (7911 knees (n = 5161 males, n = 2750 females)0 representing three regions (Asia, Europe, and South America) and two methods of data collection (dissection and X‐ray;). men had higher prevalence rates with a p-value of (P = 0.048), and prevalence rates increased through time for both men and women (P < 0.0001).  
4. Prevalence rates were highest in Asia (30.07–51.86% in 2018), followed by Oceania (29.70–51.50% in 2018), with the lowest prevalence in Africa (10.29–22.37% in 2018) and North America (12.37–26.17% in 2018).
In conclusion, the meta‐analysis provided evidence that confirms some of the genetic and environmental explanations for variations in fabella prevalence rates, As well as proposing new ones, however, there is still no definitive answers at this time in explaining the development. Ethically there may be some discrepancies in the accuracy study since there are still groups of individuals without access to proper healthcare, individuals who do not wish to participate in modern medicine, rural areas of individuals left untested. There may also be some incorrect interpretations of the study that may serve to cause an unjust racial bias towards certain groups of people, or crude assumptions of lifestyle and environment. I believe this because throughout time individuals have always tried to create a hierarchy of races and in today's world of social sciences there are individuals who have tried to use evolution and poorly done studies of people to justify racism. (i.e Watson). 

Berthaume, M.S. and Bull, A.M.J. (2020), Human biological variation in sesamoid bone prevalence: the curious case of the fabella. J. Anat., 236: 228-242. https://doi.org/10.1111/joa.13091

Pressman, Lindsay(2017), "How Evolution was used to Support Scientific Racism". The Trinity Papers (2011 - present).
Trinity College Digital Repository, Hartford, CT. https://digitalrepository.trincoll.edu/trinitypapers/59