Mindscape Ep. 342 | Rachell Powell on Evolutionary Convergence, Morality, and Mind

Sean Carroll’s Mindscape Podcast
Date: January 26, 2026
Guest: Rachell Powell, Philosopher of Biology

Episode Overview

This episode dives deep into the questions of evolutionary contingency versus convergence: Are the pathways and outcomes of evolution random and unpredictable, or are there lawful patterns and recurring solutions? Philosopher Rachell Powell and physicist Sean Carroll explore how these ideas play out in biological evolution, cognition, morality, and even in the search for life and intelligence beyond Earth. They discuss why certain forms repeatedly evolve, the unique emergence of human cumulative culture, the biological underpinnings of morality and normativity, and speculation on the long-term future of our species and others.

Key Discussion Points & Insights

1. Contingency vs. Convergence in Evolution

[00:00–16:50]

• Sean Carroll introduces the concept of vast possibility spaces in complex systems (e.g., evolution) and the tension that exists when, despite those possibilities, we see recurring features (“convergence”).
• Rachell Powell outlines the unresolved debate between evolutionary contingency (history’s unpredictability) and convergence (recurring, “inevitable” evolutionary solutions).
• The difference between physics’ universal laws (Copernican and mediocrity principles) and the contingent, quirky nature of biology is a central theme.
  • Powell: “The biggest problem that we're dealing with when it comes to the contingency question [is]...we’re dealing with an n = 1” (29:30), meaning we only have the single, unique evolutionary history of Earth as data.

Notable Quote:

“Science really is about exploding our most cherished assumptions about the causal structure of the world.”
— Rachell Powell [06:10]

2. SETI, Fermi Paradox, and Anthropocentrism

[06:30–31:54]

• Powell describes why evolutionary biologists have historically been skeptical participants in SETI (Search for Extraterrestrial Intelligence) debates — they see too much contingency in the history of life.
• The Fermi Paradox may not actually be that paradoxical from a biologist’s view, given the lack of “universal” evolutionary laws.
• Cultural narratives about extraterrestrial intelligences (e.g., humanoid aliens) often fall prey to an anthropocentric “bundling fallacy.”

Notable Quote:

“The outcomes, these earthly outcomes, are just projectable out into the universe...but none of that is really parsing traits in evolutionary history according to whether they’re contingent or replicable.”
— Rachell Powell [16:20]

3. Gouldian Contingency & the Challenge of Predictability

[17:00–31:54]

• Discussion of Stephen Jay Gould’s contingency argument: “Rewind the tape of life, let it play again,” and the outcome will likely be completely different.
• Major innovations (e.g., vertebrates, cumulative culture) are the product of myriad, individually unpredictable events.
• Even “law-like” natural selection is comparatively toothless for prediction; it describes a process, not precise outcomes.

Notable Quote:

“There are no globally optimal traits, meaning traits that are always going to be fit, always going to be optimal. So as a result, you just don't get any specific laws falling out of the principle of natural selection.”
— Rachell Powell [19:44]

4. Convergent Evolution: Real Experimental Replication?

[30:38–34:33]

• The “convergence camp” points to repeated, independent evolution of similar forms (e.g., the eye, body shapes) as evidence for law-like patterns.
• Powell cautions not to overgeneralize: What looks like convergence may result from very different processes, and not all convergence challenges contingency.
• Convergence and contingency are not strict opposites; universal solutions may emerge only at certain levels and for certain problems.

5. The Evolution and Convergence of Intelligence and Mind

[34:33–47:14]

• The human-centric view of intelligence is challenged by strong evidence for independent evolution of brains, intelligence, and even mind across multiple animal phyla (e.g., cephalopods, arthropods, birds, bees).
• Comparative cognition has shifted away from identifying “homologous” structures (e.g., where is the human brain region for consciousness?) and toward understanding function.
• Convergent “worldviews” — holistic perceptual experiences — have evolved, suggesting possible universal patterns.

Notable Quotes:

“I think ultimately extraordinary levels of cognitive flexibility and intelligence is probably a liability in the long run.”
— Rachell Powell [35:01]

“Bees...did that in half the time. There’s compelling evidence for abstract concepts in bees, like sameness, difference, and then actually transmitting that across sensory modalities.”
— Rachell Powell [43:12]

6. Culture, Cumulative Culture, and Human Uniqueness

[47:15–54:25]

• The step from intelligence to cumulative culture is massive and highly contingent, arguably unique to humans.
• For most of human history, biological capacities existed without cumulative culture — it only recently “took off.”
• The emergence of cumulative culture involved a complex accumulation of traits, not a single “smart gene.”

Notable Quotes:

“I do not think humans are smarter than, say, dolphins. I do believe that we benefit from cumulative culture and that is a tremendous difference.”
— Rachell Powell [52:39]

7. Convergence in Social Organization & Morality

[56:18–69:48]

• Classic convergence is easiest to identify in morphology, but Powell argues it also occurs in behavioral and social domains.
• When defining social/normative structures biologically (not just anthropocentrically), social insects become prime examples.
  • Social insects demonstrate “institutionalized” rule enforcement, sometimes more so than primates.
• Normative societies (rule-governed rather than power-ruled) thus emerge convergently, though with different cognitive underpinnings.

Notable Quotes:

“A normative society is...law governed and governed by rules, not sheer power, not self-interest. And I think that that's precisely what you get in all sorts of rules in social insect societies.”
— Rachell Powell [62:46]

8. Philosophy: Normativity, Morality, and Progress

[73:20–80:56]

• Morality and normativity evolved for local, functional reasons (in-group cooperation, out-group antagonism).
• Human moral progress (e.g., expansion of rights, law) is ongoing, but fragile; we’re vulnerable to regression under stress.
• Our ability to critically examine and improve our morality exists, but is constantly under threat from evolved tendencies and environmental triggers.

Notable Quotes:

“These gains are fragile because...we’re susceptible...that is what we're seeing. We're looking right now down the barrel of the fragility of our institutions.”
— Rachell Powell [80:56]

9. The Future of Humanity: Prospects and Ethical Reflections

[83:08–96:00]

• Short and long-term perspectives: Macro-evolutionarily, extinction is the rule; even knowing all the “causal levers” might not help us avert disaster.
• Powell raises the question of whether humans are domesticators of technology/AI, or whether we might become the domesticated.
• Ultimately, a macroevolutionary perspective can be “amoral” and comforting: Existence is not ethically mandated.
• Powell likens the ethical stance to the end of “Groundhog Day”: Perhaps it’s best, given uncertainty and tragedy, to focus on developing excellence and flourishing, rather than seeking to maximize or control every outcome.

Notable Quotes:

“There's nothing inevitable about this outcome...We could have easily went extinct...where we are now is such a far cry from what we were all this time that I think it's really a sobering thought.”
— Rachell Powell [50:41]

“From a macroevolutionary perspective...if there's any inference you're going to make from induction, it's that all of every species’ time is limited. And I don't think that there's an ethical imperative for existence at any cost or in any form.”
— Rachell Powell [87:23]

“I think virtue ethics...is stupid, but I think it's right.”
— Rachell Powell [93:25]
(Powell explains that, given the unpredictability of existence and our moral limitations, focusing on character and flourishing, not maximization, may be wisest.)

Memorable Moments & Quotes (With Timestamps)

• “Science really is about exploding our most cherished assumptions about the causal structure of the world.”
  — Rachell Powell [06:10]

• “The biggest problem...we’re dealing with when it comes to contingency...we’re dealing with an n = 1.”
  — Rachell Powell [29:30]

• “There are no globally optimal traits...as a result, you just don't get any specific laws falling out of the principle of natural selection.”
  — Rachell Powell [19:44]

• “I do not think humans are smarter than, say, dolphins...we benefit from cumulative culture and that is a tremendous...difference.”
  — Rachell Powell [52:39]

• “A normative society is...law governed and governed by rules, not sheer power, not self-interest. And I think that that's precisely what you get in all sorts of rules in social insect societies.”
  — Rachell Powell [62:46]

• “From a macroevolutionary perspective...all of every species’ time is limited. And I don't think that there's an ethical imperative for existence at any cost or in any form.”
  — Rachell Powell [87:23]

• “I think virtue ethics...is stupid, but I think it's right.”
  — Rachell Powell [93:25]

Structure and Flow

• 00:00–16:50: Introduction of themes; contingency vs. convergence; difference between physics and biology.
• 16:50–31:54: Evolutionary contingency and the Fermi Paradox; what convergence does and does not explain.
• 31:54–47:14: Repeated evolution of intelligence, minds, nervous systems.
• 47:14–54:25: Uniqueness of cumulative human culture, and its radical contingency.
• 56:18–69:48: Convergence in social and normative structures; redefining morality and society in biological terms.
• 73:20–80:56: The evolution of morality; fragility and progress; normativity and human vulnerability to regression.
• 83:08–96:00: Speculation about humanity’s future; ethical ramifications; learning from macroevolution and virtue.

Final Thoughts

Powell and Carroll take listeners on an interdisciplinary journey, rigorously questioning assumptions about evolution, intelligence, morality, and our place in the universe. By re-examining convergence and contingency at every level—from gene to society—they challenge anthropocentrism and universal stories about progress. The conversation ends on a reflective, almost philosophical note: rather than seeking to maximize or preserve humanity at any cost, perhaps we should focus on understanding, empathy, and flourishing within our moment.

For further reading:

• Rachell Powell & Alan Buchanan, The Evolution of Moral Progress (2018)

Acknowledgments

Thank you to Rachell Powell for a wide-ranging, incisive exploration of deep scientific and philosophical questions on Mindscape.