From a Darwinian perspective, there are only a handful at best of animals that mate for life. Humans are not one of them.
Marriage is a construct created by humans. It's purpose or original intention? Who knows? To increase two people's commitment to stay together through sociological paradigms?
Do I believe in a condition of an irresistible desire and drive to be with another, specific person?
Yes.
Do I believe that it is a permanent condition?
No.
Are Geese driven to find and be with their soulmate, not stopping until they find that ONE partner amongst a group of hundreds of millions by way of some devine or natural requirement?
I don't think so.
As far a humans? At 7 billion people on this earth, or even back when it was only a few hundred million...
I suspect that soulmate... is the same as making a choice of WHOM to love as a partner... or mate for life...