Scientists have produced monkeys with genetic material from two mothers, an advance that could help women with some inherited diseases have healthy children but which would raise a host of safety, legal, ethical and social questions if attempted in people.

Using cloning-related techniques, the researchers developed a way to replace most of the genes in the eggs from one rhesus macaque monkey with those from another, fertilized the eggs with sperm, transferred the resulting embryos into animals' wombs and produced four apparently healthy offspring.