Why human mood variation persists

Mental health problems like depression and anxiety affect enormous numbers of people and severely interfere with their lives. By contrast, we don’t see similar levels of physical ill health in young people. At any point in time, something like 20% of young people are working through anxiety or depression that’s seriously interfering with their lives — but nowhere near 20% of people in their 20s have severe heart disease or cancer or a similar failure in a key organ of the body other than the brain.

From an evolutionary perspective, that’s to be expected, right? If your heart or lungs or legs or skin stop working properly while you’re a teenager, you’re less likely to reproduce, and the genes that cause that malfunction get weeded out of the gene pool.

So why is it that these evolutionary selective pressures seemingly fixed our bodies so that they work pretty smoothly for young people most of the time, but it feels like evolution fell asleep on the job when it comes to the brain? Why did evolution never get around to patching the most basic problems, like social anxiety, panic attacks, debilitating pessimism, or inappropriate mood swings? For that matter, why did evolution go out of its way to give us the capacity for low mood or chronic anxiety or extreme mood swings at all?

Today’s guest, Randy Nesse — a leader in the field of evolutionary psychiatry — wrote the book Good Reasons for Bad Feelings, in which he sets out to try to resolve this paradox.

Rebroadcast: This episode originally aired in February 2024.

Links to learn more, video, and full transcript: https://80k.info/rn

In the interview, host Rob Wiblin and Randy discuss the key points of the book, as well as:

• How the evolutionary psychiatry perspective can help people appreciate that their mental health problems are often the result of a useful and important system.
• How evolutionary pressures and dynamics lead to a wide range of different personalities, behaviours, strategies, and tradeoffs.
• The missing intellectual foundations of psychiatry, and how an evolutionary lens could revolutionise the field.
• How working as both an academic and a practicing psychiatrist shaped Randy’s understanding of treating mental health problems.
• The “smoke detector principle” of why we experience so many false alarms along with true threats.
• The origins of morality and capacity for genuine love, and why Randy thinks it’s a mistake to try to explain these from a selfish gene perspective.
• Evolutionary theories on why we age and die.
• And much more.

Chapters:

• Cold Open (00:00:00)
• Rob's Intro (00:00:55)
• The interview begins (00:03:01)
• The history of evolutionary medicine (00:03:56)
• The evolutionary origin of anxiety (00:12:37)
• Design tradeoffs, diseases, and adaptations (00:43:19)
• The tricker case of depression (00:48:57)
• The purpose of low mood (00:54:08)
• Big mood swings vs barely any mood swings (01:22:41)
• Is mental health actually getting worse? (01:33:43)
• A general explanation for bodies breaking (01:37:27)
• Freudianism and the origins of morality and love (01:48:53)
• Evolutionary medicine in general (02:02:42)
• Objections to evolutionary psychology (02:16:29)
• How do you test evolutionary hypotheses to rule out the bad explanations? (02:23:19)
• Striving and meaning in careers (02:25:12)
• Why do people age and die? (02:45:16)

Producer and editor: Keiran Harris
Audio Engineering Lead: Ben Cordell
Technical editing: Dominic Armstrong
Transcriptions: Katy Moore