Nazi Doctor Mengele Had Advanced Medical Techniques

Produced an extremely high rate of twins in a Brazilian town. How did he do it? It's not even clear to me that doctors today could produce twins like this. Was there artificial insemination or some other technique used? Even artificial insemination (with semen) wouldn't produce identical twins-- it would have to be in vitro fertilization where the embryo was specially treated before implantation. There's also evidence that Mengele had special animal knowledge too. How could he have possibly done this alone? Who helped him?