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.
The first day of bleeding is day one. Let's say you bleed for about five to seven days and then have sex four days afterwards. If you had sex four day after a five day period then you had sex on about day nine of your cycle and if you ovulate between day 10 and day 13 then you have higher chance of getting pregnant.