Did you know that 8 to 16 percent of humans are missing the Palmaris longus muscle which was once used for climbing.
We examined 300 Caucasian subjects (150 males, 150 females) aged 18-40 years to assess the incidence of palmaris longus absence. The presence or absence of palmaris longus was assessed by clinical inspection. Forty-nine subjects had unilateral absence of palmaris longus (16%).
The tendon was absent bilaterally in 26 subjects (9%). Unilateral and bilateral absence was more common in males, however this was not statistically significant (p = 0.25 and 0.56 respectively). In those subjects with unilateral absence, the right side was found to be more commonly affected however no statistical significance was evident (p = 0.25).