For most of our history, humans have been extraordinarily ignorant about sex. Consider, for instance, that up until 1930 we did not know the most fertile period of a woman's reproductive cycle. In other words, we didn't really know the best way to make babies, or avoid making babies, for that matter.

Today, there is still much about sex that we either don't know or don't agree on. 

For instance, Robert Martin makes the argument in his book How We Do It: The Evolution and Future of Human Reproduction that a woman's fertile period is much longer than we believe it is. Martin has gathered a set of evidence that shows that sperm can actually survive up to 10 days in a woman's womb. 

While this claim is controversial, Martin has a broader, and equally controversial claim to make about sex. 

Martin tells Jeff Schechtman in this week's Specific Gravity podcast that fundamental conflicts exist between the medical community on the one hand and the field of evolutionary biology on the other. The medical community, in Martin's view, does not reflect enough about our evolutionary history, which can help us to understand fundamental biological processes as well as give us new insights on how to cure diseases.

Take, for instance, the issue of breastfeeding. How long should a woman breastfeed a child? It is difficult to know what is biologically appropriate. 

The key to answering this question is evolutionary thinking.

"You can look at primates generally and predict what the breast feeding period should be," Martin says. And the answer, to be conservative, is that "we are biologically programmed for our babies to be breastfed for three years."

In the podcast below, Schechtman and Martin explore the concept of Darwinian medicine, which is the bringing of Darwinian ideas to practice in contemporary medicine. Have we stopped evolving? If not, what evolutionary changes have occurred relatively recently? We currently have an epidemic of reproductive cancers. How can evolutionary biology help us understand why?

Listen to the interview here: