I have not heard this in Africa but I have heard some people in America and in other western countries make arrangements with science research institutions to use their bodies for science experiments after they are dead and gone.
Some also donate just certain organs in their bodies so that when they die those organs can be used to help save lives. Saving lives is the duty of every Christian, every Muslim, every Jewish, etc. Donating organs such as one of your kidneys while alive can help save lives and donating some of your organs after death can also help save lives. Donating blood can and do help save lives. Some of my Christian friends in Africa especially the Jehovah Witnesses do not donate blood and they do not accept blood even in critical conditions.
A Jehovah witness died in my community in Africa because his parents refused blood transfusion for him although the parents are rich enough to afford the blood transfusion. Not just the Jehovah Witnesses in Africa but all Jehovah Witnesses do not permit blood transfusion because they consider blood transfusion a great sin.
I read it somewhere that Islam is against blood transfusion and organ donation but they still permit it under certain critical conditions. I know Catholics permit blood donation but I don't know whether Catholics permit organ donation. I don't know much about Hinduism and the other religions. I read a touching story on yahoo news a few days ago about a teenage girl whose life was saved by one good Samaritan. The good Samaritan donated one of his kidneys to save the poor girl who needed a match urgently. I don't think God will consider such a generous act a sin but some Christians and other religious people are against organ donation and organ transplant.
Some like the Jehovah Witnesses, are against even blood transfusion. What do you think? Is it a sin to donate blood and organs to save lives?