What relevance, if any, does Charles Darwin and evolutionary biology have for libertarianism? This issue is being debated this week over at Cato Unbound, by University of Northern Illinois philosopher Larry Arnhart, University of Minnesota biologist PZ Myers, Santa Fe Institute behaviorial scientist Herbert Gintis, and Rutgers University anthropologist Lionel Tiger.

Arnhart, author of Darwinian Natural Right: The Biological Ethics of Human Nature, argues that Darwin and the findings of evolutionary biology do offer support for the normative claims of classical liberalism. Arnhart defines classical liberalism as

the moral and political tradition of individual liberty understood as the right of individuals to be free from coercion so long as they respected the equal liberty of others. According to the liberals, the primary aim of government was to secure individual rights from force and fraud, which included enforcing laws of contract and private property. They thought the moral and intellectual character of human beings was properly formed not by governmental coercion, but in the natural and voluntary associations of civil society.

On my reading, Arnhart is arguing that classical liberalism better conforms to what evolutionary psychology is confirming about human nature. Societies whose institutions try to go against human nature will do less well than societies whose institutions enable the flourishing of our natures. But if that is so, why is it that truly liberal societies have emerged only in the past two centuries? After all, human nature has not changed much in the past several millennia. (My personal answer is the cultural evolution is a trial-and-error process that is slowly discovering institutions that increasingly conform better to human nature.)

So far, only Myers has responded to Arnhart arguing that he claims too much. Meyers asserts:

Evolution gives us only very general rules for our species. Adapt to the environment, or die. Change is inevitable.

Question to Myers: Just what social and economic systems better recognize and enable people to adapt and change? Possibly those based on the principles of classical liberalism?

Myers points out that all kinds of political tendencies have tried to wrap themselves in the blanket of Darwinian science, including the Revolutionary Communist Party. After all, Karl Marx famously asked Darwin if he might dedicate the first volume of Das Kapital to him. Darwin turned down the honor. I don't know what the Revolutionary Communists might be up to, but at least one prominent leftist, Princeton philosopher Peter Singer, argued that findings of evolutionary biology about human nature do put constraints on leftist social policies. Singer makes these limits explicit in his book, A Darwinian Left: Politics, Evolution, and Cooperation.

To illustrate Singer's thinking, let me share some excerpts from my 2000 interview with him on this topic:

Reason: Let me put it differently: What limits should be set on a program of egalitarianism?

Singer: Right, right. That's a different question. I think the limits ought to be essentially those that can be achieved without the kind of authoritarianism that would be incompatible with fairly liberal democratic traditions and without enormous costs and enormous loss. You have to consider whether you're going to trade off some element of the total overall prosperity of a society for the sake of having it be more egalitarian. I think those are questions of judgment. I think it's reasonable to trade off some measure of that, but obviously not enough to create a widespread hardship....

Reason: What does Darwinian thinking tell the left about why so many of the social programs they have favored have had difficulties or have failed?

Singer: It tells the left that some of them have failed because their goals were really unrealistic. For example, if their goals were to achieve equality and to combine that with a high degree of liberty--to have the state withering away, as Marx said--it's very difficult to see how you're going to be able to achieve that. If you let the state wither away, then humans' natural tendencies to form hierarchies and rank and so on are going to assert themselves. What happened specifically with the form of communism that was attempted in the Soviet Union and Eastern Europe was that people went into it with some vague idea that they could have this sort of society. But they kept needing to strengthen the power of the state rather than allow it to wither away. In that sense, the original idea would just collapse. You simply couldn't achieve it. Human beings are not such that you could expect them to work for the common good in the way that the theory assumed. The failure to understand that human nature is not as plastic as socialists often assume is a substantial part of why some of these schemes have failed.

Myers concludes his response to Arnhart by asserting:

Evolution does not incline us to classical liberalism; it is just one of many options that evolution allows.

Indeed, evolution per se may not so incline us, but as both Singer and Arnhart are arguing (I think convincingly) our human natures honed by evolution may do so.

Go here to enjoy the exchange on the social and political implications of evolutionary science.