Complete recirculation takes 10 million years , thus any organic compounds produced by then would be altered or destroyed by temperatures exceeding 300 Â C. They estimate that the development of a 100 kilobase genome of a DNA\/protein primitive heterotroph into a 7000 gene filamentous cyanobacterium would have required only 7 million years . Complete recirculation takes 10 million years , thus any organic compounds produced by then would be altered or destroyed by temperatures exceeding 300 Â . They estimate that the development of a 100 kilobase genome of a DNA\/protein primitive heterotroph into a 7000 gene filamentous cyanobacterium would have required only 7 Ma .