Race differences in ball size is a fascinating topic. Why are European balls so big? They are much larger than African and East Asian ones. That's an unusual deviation from the usual three-way Rushton pattern. Jared Diamond published on this in 1986.
nature.com
nature.com
We did a partial replication using American army data:
researchgate.net
researchgate.net
If someone can find more studies of race and ball size, please let me know! It would be good to do a meta-analysis of whatever studies exist. There are 89 papers that cite Diamond's 1980s paper. Good place to start looking.
scholar.google.dk
scholar.google.dk
No gaps in babies, but not too surprising as presumably these mainly arise in puberty. Though it is true that brain sizes arise already in utero.
academic.oup.com
academic.oup.com
Study finds Gypsies got bigger balls than Hungarians.
Also provides a review of other studies. Best source so far!
link.springer.com
Also provides a review of other studies. Best source so far!
link.springer.com
This otherwise p-hacked Korean study shows normal testis size in Korean men, contradicting the other Asian data based on Chinese men.
synapse.koreamed.org
synapse.koreamed.org
Dutch child and adolescent (actually adult) data. Looks good! Provides a growth chart for both orchidometer and ultrasound (gold standard).
pubmed.ncbi.nlm.nih.gov
pubmed.ncbi.nlm.nih.gov
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