| Interesting article on the median artery given that there is no proposed advantage to the phenotype that is increasing in representation. My understanding is that evolution is specifically directional change in response to a pressure, not random drift or coincidence. Is it accurate to say a trait evolved if the change in prevalence is entirely incidental and tied to a second Factor? Is it accurate to say a trait evolved if the change is a regression to the mean in the absence of pressure? I went looking for papers on why the median artery might be selected for, and one hypothesized that it may be grouped with, fetal deformities, such as spina bifida, which are increasing not because they are advantageous, but because adverse selection pressures are diminished. Another hypothesis is that the variation in median artery is not reflective of a change in genome, but change in environmentally triggered gene expression associated with maternal health. |
Nobody seems to have studied the effects of a persistent median artery on dexterity (important amidst increasing literacy and now phone/computer use) or forearm circumference (looks hot).