The basic problem is that the human species is programmed to want to start families at age 16 - 20, and not 25 - 35. The solution is that it has to again become both economically and socially possible for people to marry and start families in their late teens and early twenties, as was the norm in 1850.
Exactly. Young people of marriageable age are not being encouraged towards marriage, rather they are told to "party" and "have fun" and focus on developing their education. I am discussing "socially possible" for early marriage and starting a family, here: There is no reason encouraging education and career development can't occur along with encouraging young people towards marriage.