The first human cloned embryo could be implanted into a surrogate mother’s womb before the end of the year, US fertility expert Panayiotis Zavos claimed on Monday.

Zavos says he created the human cloned embryo by fusing an empty human egg with a granulosa cell. The embryo, which was frozen after growing to a ball of eight to 10 cells, was created after Zavos had experimented for months with hybrid embryos made by fusing human cells with empty cow oocytes.

To make female hybrids, he fuses the empty cow oocytes with granulosa cells from women. And to make male hybrids, he fuses the empty cow oocytes with differentiated forms of fibroblast skin cells taken from men.