The species theory, polygenism, held that human races were of different lineages and suggested a hierarchy outlined in the Chain of Being that positioned Africans between man and lower primates.
No, they are involved in the Circulatory System which is responsible for pumping and channelling blood to and from the body and lungs with heart, blood and blood vessels. no veins are not considered an organ because they are a grouping of different tissues like a organ.
In biology, an organ or viscus is a collection of tissues joined in a structural unit to serve a common function. In anatomy, a viscus (/ËvÉªskÉs/) is an internal organ, and viscera (/ËvÉªsÉrÉ/) is the plural form. Organs are composed of main tissue, parenchyma, and sporadic tissues, stroma. The main tissue is that which is unique for the specific organ, such as the myocardium, the main tissue of the heart, while sporadic tissues include the nerves, blood vessels, and connective tissues.