At the time of the film's release, the possibility of de-extinction seemed fantastical. Subsequent advances in technology, however, have made that possibility a growing reality. In 2003, for example, a team of scientists used preserved DNA to create a clone of an extinct species of goat called the bucardo. Although the clone died shortly after birth, the event marked the first documented case of de-extinction.
What is the meaning of fantastical as used in the passage?