Why does obama's birt certificate state his race as "african" and not "*****" as was accepted back than?

why does obama's birth certificate state his race as "african" and not "*****" as was accepted back than? Before the 1970's nobody used the term "african", only "*****" so why does obama's say "african"? Is it a forgery? Also, why did he not release it right away if he had it all along?