You can come closer to "evidence" if you dive into anthropology. The only way to find out what works for humans as a race is to observe human societies worldwide in current and historical times. In addition, mtDNA provides clues about what worked for humans in prehistoric times. No society is the same, all do their things in different ways, but some patterns emerge, and serial monogamy is one of them.

Anthropologists today agree that humans seems to be "serial monogamous with occasional non-monogamy". This is considered the "natural state" of our biology based on current, historical and pre-historic evidence.

Biology is otherwise a tricky concept since culture plays such a strong role in how humans "naturally" act. But anthropologists have come to these conclusions not only through observing behavior but also through complex statistical analysis on the material aspect of human existence, among other things the factors that drive sex, procreation and reproductive fitness in men and women all over the world.