Did Darwin Kill Morality?

According to some philosophers Darwinian evolution offers us an explanation for our moral judgements that does not rest on moral truth and thus undermines our reason to trust those judgements. In this Darwin threatens morality. This episode of the P-Value introduces the idea of evolutionary debunking. What does the debunker's challenge entail? And, should we be persuaded by it?

Key References: 

• Ruse (1986) Evolutionary Ethics: A Pheonix Arisen. Zygon, 21(1):95-112.
• Street (2006) "Darwinian Dilemma for Realist Theories of Value" Philosophical Studies, 127(1): 109-166.
• "Evolutionary AntiRealism - Early Efforts" from James, Scott M. (2011) An introduction to evolutionary ethics. Wiley Blackwell Oxford.

Note: This episode is based on a transcription of an original lecture of the same name by Dr. Rachael Brown. That material was adapted into a format suitable for podcast delivery with the assistance of ChatGPT (OpenAI).

Transcript

 Imagine a species of intelligent aliens arrives on Earth.

As a way of marking the discovery of other intelligent life, they celebrate.

And part of that celebration involves killing—and eating—some of the offspring they’ve had on the journey.

Most, if not all, of you will find that deeply repulsive.

But now suppose we learn something more about them.

They come from a harsh, unstable environment. Resources are scarce, and most offspring don’t survive to adulthood.

Over evolutionary time, they’ve developed a strategy.

They reproduce—and then, in some cases, they kill a portion of their offspring and consume them.

Not out of cruelty. Not out of indifference.

But because, in their environment, doing so increases the chances that some of their offspring survive—and that they themselves reproduce again.

From their perspective, this isn’t a failure of care or cruelty.

It’s a successful strategy.

And yet…

most, if not all, of you will still think that what they’re doing is deeply wrong.
 
 So here’s the question we are going to focus on today.
 
 Not is the behaviour morally acceptable?
 
 but rather,
 
 what explains our judgment that it isn’t?
 
 And more importantly:
 
 what follows from that explanation?

Because if the answer is just that our reaction is the product of our evolutionary history—then we need to ask a further question.

Are we discovering something about the world when we make moral judgments…

or are we just expressing the kind of creatures we happen to be?

 
 MUSIC
 
 In this episode, I want to explore the question:
 
 Did Darwin kill morality?
 
 In the origin Darwin didn’t just give us a theory of biological change.
 
 He gave us a way of understanding ourselves—our bodies, our minds, our behaviours—as products of evolutionary history.
 
 And importantly, he placed us firmly within the animal kingdom.
 
 From a Darwinian Perspective our moral psychology—our sense of right and wrong, our feelings of guilt, empathy, obligation—should also be understood as evolved traits rather than designed by a god, or founded in a soul or supernatural spirit.
 
 And that raises a question.
 
 Given our moral judgments are shaped by evolution…
 
 what happens to their authority?
 
 Let’s go back to our aliens.
 
 What makes their behaviour feel so clearly wrong to us?
 
 One natural answer is that we are the kind of creatures who invest heavily in our offspring.
 
 Human children are dependent for a long time. They require care, protection, resources.
 
 So it’s not surprising that we have strong emotional responses—attachment, empathy, guilt—around parenting and harm to children.
 
 Those responses are not random.
 
 They are, at least plausibly, the product of evolutionary pressures.

And it’s not just parenting.

Think about things like fairness—our strong reactions to cheating, to free-riding, to people taking more than their share.

Or our tendency to feel resentment when someone harms us, and guilt when we harm others.

These aren’t random either.

They look very much like mechanisms for stabilising cooperation in groups like ours.
 
 So one way of thinking about morality is this:
 
 It’s an evolved system for regulating social behaviour.
 
 And on that picture, our reaction to the alien case isn’t tracking some independent moral truth.
 
 It’s expressing the kind of creatures we are.
 
 Short pause
 
 But that raises a further question.
 
 Even if evolution explains why we have the moral beliefs we do…
 
 does that does that explanation support, undermine, or leave untouched our justification for thinking those beliefs are true?

In other words, does explaining where our moral beliefs come from help to justify them…

or does it give us reason to doubt them?

What makes our strong belief that killing innocent babies is wrong, reasonable or justified?
 
 And this is where things get more complicated.
 
 One of the most influential ways of pressing this issue comes from Sharon Street.
 
 Street argues that evolutionary theory puts pressure not on whether moral truths exist…
 
 but on whether we are justified in believing our moral judgments track them.
 
 And that’s an important distinction.
 
 She is not claiming that morality is false.
 
 Rather she asks whether, given how our moral beliefs have been shaped, we have reason to doubt that they are reliable guides to whatever moral truth there might be?
 
 She frames this as a dilemma of the following form.

Premise 1: evolutionary forces have had a significant influence on the content of our moral beliefs.

Premise 2: those evolutionary forces track survival and reproduction not moral truth.

Conclusion We have reason to doubt that our moral beliefs reliably track moral truth.

And importantly, that’s a claim about justification, not about whether moral truths exist.

And notice what’s doing the work here.

It’s not just that evolution influences our beliefs.

It’s that the process shaping those beliefs is not aimed at truth.

And that’s what creates the problem.

 
 On the one hand, we might say our moral beliefs track objective moral truths.
 
 But on the other hand, we have a strong evolutionary explanation for why we hold those beliefs—
 
 an explanation that appeals to survival and reproduction, not truth.
 
 So what’s the relationship between these two things?
 
 Street argues that there are really only two options here.

The first is that evolutionary forces have somehow tracked moral truth—that what helped our ancestors survive also happens to be morally right.

But this looks like a coincidence. Evolution selects for fitness, not truth, so why think it would align with moral truth?

The second option is that our moral beliefs have been shaped independently of any moral truth.

But if that’s right, then the explanation of why we hold those beliefs makes no reference to their truth—and so we seem to lose any reason to think they are true.

One way to see the worry is with an analogy.

Imagine a device that gives you answers to mathematical questions—but its answers are generated by a process that has nothing to do with mathematics.

Even if it sometimes gets things right, you wouldn’t trust it.

And the concern is that our moral beliefs might be like that—shaped by a process that tracks survival, not truth.

And that’s the dilemma: either an implausible coincidence, or a loss of justification.

Given we typically think knowledge of anything requires justification, we are in trouble. 
 
 MUSIC

A related, and in some ways more radical, position is defended by Michael Ruse.

Ruse pushes the evolutionary story a step further.

Where Street argues that evolution undermines our justification for moral beliefs, Ruse suggests something stronger—that morality itself may be, in a sense, an illusion.

Now, that doesn’t mean that moral claims don’t matter, or that we should stop using them.

The idea is subtler than that.

According to Ruse, natural selection has equipped us with a strong tendency to see certain behaviours—like harming others, or breaking promises—as objectively wrong.

But that tendency wasn’t selected because it tracks moral truth.

It was selected because it helps us cooperate.

If individuals in a group believe that certain rules are objectively binding—not just convenient—then they are more likely to follow them.

And groups that coordinate in this way tend to do better.

So on this view, our sense that morality is objective—that some things are really right or wrong—is itself a product of evolution.

It’s part of the mechanism that keeps social systems stable.

And that leads to a more unsettling possibility.

It may be that morality doesn’t just fail to track an independent truth.

It may be that the appearance of moral truth is something evolution has constructed.

A kind of useful fiction.

Something that feels real to us, because it plays an important role in how we live together.

And if that’s right, then the challenge isn’t just about whether our moral beliefs are justified.

It’s about whether there is any moral truth there to be tracked at all.

If Ruse is right, our reaction to the alien case looks different.

It’s not that we’re detecting something objectively wrong in what they’re doing.

It’s that we’ve been shaped to experience it that way.

MUSIC
 
So, if Street is right, we lose justification; if Ruse is right, we may lose morality itself.

At this point, you might want to resist the debunker’s conclusion.

A natural response is to say something like this.

Even if evolution has shaped our moral starting point, it doesn’t follow that we are stuck with it.

We also have the capacity for reason.

We can reflect on our beliefs.
 We can criticise them.
 We can ask whether they are consistent, whether they generalise, whether they can be justified.

And on this picture, reasoning is not just another evolutionary adaptation.

It is a way of stepping back from our initial intuitions and evaluating them.

This kind of view is often associated with philosophers like Thomas Nagel.

Nagel argues that, at least in some domains, we are capable of a kind of objective reasoning—a capacity to assess our beliefs from a more impartial standpoint.

So even if evolution explains why we start where we do, it doesn’t follow that it determines where we end up.

And if that’s right, then the debunking argument may be too quick.

It assumes that because our beliefs have evolutionary origins, they cannot be justified.

But that would only follow if reasoning itself were entirely shaped by those same evolutionary forces.

And that’s exactly what this objection denies.

Short pause

But here’s the difficulty.

Even if we grant that we can reason…

what are we reasoning from?

And this is the key tension.

Reason may allow us to improve our beliefs—but it starts from materials that evolution has already shaped.

So the question is whether reason can genuinely take us beyond those starting points…

or whether it just reorganises them.

Our starting points—our intuitions, our emotional responses, our sense of what matters—are themselves shaped by evolution.

And reasoning doesn’t operate in a vacuum.

It works on those starting points.

It systematises them.
 It extends them.
 It makes them more consistent.

But it’s not obvious that it can take us completely beyond them.

So the worry is this.

Even if reasoning improves our moral beliefs, it may still be refining a set of beliefs that were shaped for survival, not for truth.

And if that’s right, then the original challenge returns.

How would we know if our reasoning has actually tracked moral truth…

rather than just making our evolutionary starting points more coherent

 
 We began with a simple case.
 
 A species for whom killing some of their offspring is not just common—but adaptive.
 
 And we asked:
 
 what makes that wrong?
 
 What we’ve seen is that evolutionary theory gives us a powerful explanation of why we have the moral intuitions we do.

But once we have that explanation, we face a choice.

We might follow Street, and worry that our moral beliefs are no longer justified.

We might follow Ruse, and worry that morality itself is, in some sense, an illusion.

Or we might try, with Nagel, to defend the idea that reason can still get us to moral truth.

But none of those options is straightforward.

And that’s why Darwin hasn’t simply killed morality.

But he has made it much harder to explain what it is, and why we should trust it.

What do you think?
 
 That’s all for this episode.
 
 See you next time.