Another factor is that body mass is highly correlated to brain mass:<p><a href="https:&#x2F;&#x2F;www.cfa.harvard.edu&#x2F;~ejchaisson&#x2F;cosmic_evolution&#x2F;docs&#x2F;images&#x2F;imgs_sml_ver3&#x2F;7_13.gif" rel="nofollow">https:&#x2F;&#x2F;www.cfa.harvard.edu&#x2F;~ejchaisson&#x2F;cosmic_evolution&#x2F;doc...</a>