In antiparallel DNA, one strand runs from 5´ to 3´ prime and the other strand runs form 3´ to 5 ´. This configuration allows the DNA strands to form complementary pair their nucleotides using hydrogen bonds. This configuration allows for the enymes of DNA replication to function.
If the DNA strand was parallel, replication would not be possible. The nucleotides would not be complementary to each other and, as a result, would not pair in a genetic molecule. Therefore, the DNA being antiparallel is the only way replication and life could occur.