Africans were also used in large numbers for slavery because they were easier to buy. During the beginning of the Atlantic Slave Trade, Africans were willing to sell other Africans as slaves to Europeans because they had their own system of slavery.
You could have sex towards the end of your bleeding and then actually conceive 4 or 5 days later with your early ovulation. The probabilities of getting pregnant while on your period are low, but the possibilities are there. This is not the time to have sex if you are trying to get pregnant.
Ovulation can be delayed by a number of factors including stress, illness, diet, or increased physical activity. If you are trying to get pregnant, having sex a couple days before you ovulate and the day you ovulate will give you the best chances of getting pregnant. If you are trying to avoid pregnancy, you will want to not have sex a week before ovulation until 2 days after you have confirmed ovulation. The absolute best way to avoid pregnancy if you are sexually active is to use contraceptive protection or not have sex at all.