Complex sentence: The OPV AIDS hypothesis has, however, been rejected within much of the medical community and is contradicted by at least one article in the journal Nature, which claims the HIV-1 group M virus originated in Africa 30 years before the OPV trials were conducted.
Split into simpler sentences: The OPV AIDS hypothesis has, however, been rejected throughout the scientific community and is contradicted by modern research on the origin of the disease. The HIV-1 group M virus had originated in Africa 30 years before the OPV trials were conducted.