It is human because it involves human beings. It is significantly human because no human is insignificant.
Not significantly on the rise in the US.
The human race would probably continue to reproduce even if the institution of marriage were to cease to exist; certainly the human race predates marriage. I believe that marriage is a useful arrangement at least for some people, but I doubt that it is important for the continuity of the human race.
You combine a human with a human.
marriage
probably, they are significantly larger than us.
Surprisingly, the arms of a T. rex were significantly stronger than those of a human.
The best instance in human life is during birth and marriage.
Erosion is a natural process, but human actions can speed it up significantly.
Edvard Westermarck
It is an institution of bondage for a woman
No. Marriage is part of human society and values.
You will likely be significantly wealthier if you are married to a Broadway producer, but increased wealth will not make your life or marriage better. A good marriage is based on love and trust, and if you find that with a plumber, that is the far better marriage.