Its an amazing phenomenon... that's helping scientists study the origins of the genes that control how embryos develop in all living creatures.

Not only do the coral of the Great Barrier Reef spawn together, the timing of the event can be predicted meaning plenty of coral embryos can be collected to study.

Using the scanning electron microscope, scientists from the ANU Research School of Biological Sciences are able to reconstruct the sequence of development of coral embryos. And the reason these coral embryos are so fascinating is because they are living fossils, and though many times removed, are related to... humans.

Coral branched off the evolution tree millions of years ago, and while other creatures went on to evolve into far more sophisticated beings, the coral didn't. Yet they, and all other organisms, share many of the genes that control early development.

Two of the most interesting classes of genes are the HOX and PAX genes, which because they evolved early, are shared by all animals.

The HOX genes tell cells their position along the animal's body. For example in insects they determine the position of the legs and wings.

These purple cells within the coral embryo show the location of one of the PAX genes, which in higher animals says "form an eye". Corals lack eyes but still have the gene, so the question is - What does the gene do in them?

Answering questions like this could help scientists determine how the human genes have evolved. And in the process, the new knowledge gained about coral reproduction can be used to conserve one of the natural wonders of the world.