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.
They are a group of cells having the same origin, structure and function. The cells look the same or almost the same. The work the cells do is also the same or almost the same. Kinds include muscles, nerves, and connective tissues. Organs are made up of more than one kind of tissue. The heart is an organ. It is made up of different tissues. It has muscle tissue called myocardium. It has connective tissue on the inside (endocardium), and on the outside (pericardium).