In this very thoroughly researched, highly documented, and well-illustrated paper Tiedemann demonstrated that there are no significant anatomical differences between the brains and mental capacities of Black people and White people.

"I take the liberty of presenting to the Royal Society a paper on a subject which appears to me to be of great importance in the natural history, anatomy, and physiology of Man; interesting also in a political and legislative point of view. Celebrated naturalists, Camper, Soemmerring, and Cuvier, look upon the Negroes as a race inferior to the European in organization and intellectual powers, having much resemblance with the Monkey. Naturalists of less authority have exaggerated this opinion. Were it proved to be correct, the negro would occupy a different situation in society from that which has so lately been given him by the noble British Government. I propose in this treatise to examine more minutely the most important part of this doctrine, namely, the structure of the brain, the noblest part of the human body, in reference to its functions. A comparison between the brain of the Negro and that of the European and the Orang-Outang, hitherto much neglected, appeared to me most worthy of attention. I shall first of all try to answer the following two questions.

"1st, Is there any impotant and essential difference between the structure of the brain of the Negro and that of the European? and

"2ndly, Has the brain of the Negro more resememblance to that of the Orang-Outang than the brain of the European?

"Should our researches induce us to answer these questions in the affirmative, we should then have reason to consider the opinion given above as true, and founded in nature. Should we be able to pove the falsity of this opinion, we should then be allowed to consider it as a mere literary fancy....(pp. 497-98).

"The intellectual faculties of the Negroes do not in general seem to be inferior to those of the European and other races. Such of them as are not bodily and morally degraded by slavery and oppression, have a pleasing and open xpression of coutenance, and are of a gay and cheeful turn. They exhibit proofs of good natural capacity, good sense, wit and penetration....many instances of Negroes who made a cetain progress in the liberal arts and sciences, and distinguished themselves as clergymen, philosophers, amthematicians, philogians, hsitorians, advocates medical men, poets, and musicians. Many Negroes ahve distingusiehd themselves by their talents in military tacts and politics....

"The principle result of my researches on the brain of the Negro, is, that neither anatomy nor physiology can justify our placing them beneath the Europeans in a moral or intellectual point of view...." (p. 525).

Digital facsimile from the Royal Society at this link.