Given that Tim is a philosopher who researches how biology informs morality, and Monty is an anthropologist who researchers how culture shapes who we are, you won't be surprised to hear that in this episode, Tim and Monty disagree (quite a lot) about whether there is such a thing as "human nature". They in turn draw on evolutionary biology, cultural observations, twin studies, philosophy (Chinese and western) and psychology to make their points, and even find a couple of points to agree about in the end.

Boys will be boys, and girls will be girls. Or will they? A lot of people think that if you're born with a certain set of chromosomes and particular genitalia, then your gender is set for life. But things aren't that simple. They never are.

So how does sex relate to gender? Tim and Monty discuss what the latest science, anthropology and philosophy have to say about gender, and look at how sex and gender inform who we are.

Are we naturally violent creatures that are tempered by culture? Or are we naturally peaceful and it's our culture that turns some of us violent? Tim and Monty discuss this (perhaps false) dichotomy and talk about what evolution and anthropology can tell us about the origins of violence.

Sex is everywhere. It shapes our biology, it steers our behaviour, it permeates our society. It's not only about reproduction, sex serves an important social function too. Tim and Monty go back to the roots, if you will, looking at the evolution of sex - including why humans have bigger penises than gorillas and smaller testicles than chimpanzees - to understand what sex means for us today.