Genes, Brains and Behaviour

In my recent post on Conscious Robots, CR commented:

[I]f there is a behaviour that is generally seen in most humans, then at some point in our evolution, that behaviour must have increased the survival chances of our genes.

(See also the email quoted previously.)

It seems to me that CR's comments are based on an impoverished understanding of evolutionary biology. It simply isn't true that every feature of an organism is an adaptation. Everything has evolved, for sure, but natural selection is not the only evolutionary force. Genetic drift, for example, can have very significant effects, especially on smaller populations.

Stephen Jay Gould has written extensively on the importance of evolved non-adaptive traits (what he calls 'spandrels'):

All organisms evolve as complex and interconnected wholes, not as loose alliances of separate parts, each independently optimized by natural selection. Any adaptive change must also generate, in addition, a set of spandrels, or nonadaptive byproducts. These spandrels may later be "co-opted" for a secondary use. But we would make an egregious logical error if we argued that these secondary uses explain the existence of a spandrel. I may realize someday that my favorite boomerang fits beautifully into the arched space of my living room spandrel, but you would think me pretty silly if I argued that the spandrel exists to house the boomerang. Similarly, snails build their shells by winding a tube around an axis of coiling. This geometric process leaves an empty cylindrical space, called an umbilicus, along the axis. A few species of snails use the umbilicus as a brooding chamber for storing eggs. But the umbilicus arose as a nonadaptive spandrel, not as an adaptation for reproduction. The overwhelming majority of snails do not use their umbilici for brooding, or for much of anything.
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The human brain must be bursting with spandrels that are essential to human nature and vital to our self-understanding but that arose as nonadaptations [...] The brain did not enlarge by natural selection so that we would be able to read or write.
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In summary, Darwin cut to the heart of nature by insisting so forcefully that "natural selection has been the main, but not the exclusive means of modification"--and that hard-line adaptationism could only represent a simplistic caricature and distortion of his theory.

CR continues:

The generally accepted belief is that we humans are somehow ‘more than evolution’: that something about our brains has allowed us to break free and start doing ‘what we like with our lives’. [...] We need to ask ourselves how we can be more than evolution. And we need to approach it from a scientific point of view, not from your personal experiences of life. That’s very important!

I don't know what 'more than evolution' is supposed to mean. Regardless, there's a methodological issue here, in that CR seems to be advocating dogmatic adherence to his favoured theory over the raw data (of personal experience). But theories are beholden to the data, not the other way around. If a theory doesn't fit the known facts, then so much the worse for that theory!

(Of course, there are times when science shows us that common-sense is spectacularly mistaken. I'm not denying that. But even (especially!) revolutionary theories must fit the known facts - it's just our conceptual interpretations of these that change.)

It's also important to note that psychology is the science of human behaviour. If we want to translate this field into the language of biology, we need to do so in a way that maintains the integrity of the primary scientific findings. If someone proposes a biological account of human psychology that is inconsistent with our best psychological science, then the attempted secondary account has clearly failed. We need a biological explanation that complements, rather than contradicts, the primary data of psychology.

As a striking example of this, when I pointed out that people can act from a variety of motivations, CR responded: "How could we? nothing has programmed us to act from any motivation other than the maximisation of our genetic survival chances." But this is foolish, because it's obvious - a known fact - that we really can be motivated by all sorts of different reasons. Any theory that denies this is simply wrong. Similarly, it is a known fact that the human brain is a very complicated organ, capable of (some degree of) logical thought and open-ended decision making. We can make bad decisions - bad for us, even bad for our genes. It happens, there's no denying any of this.

Of course, evolutionary theory doesn't actually deny any of this - it's CR's misinterpretations of the theory that cause these problems. But I still have to show that evolution really is consistent with the facts I mentioned above. As CR writes:

What you're suggesting is that natural selection can create a brain that is capable of doing something that wont enhance the survival chances of its genes. But you're going to have to explain how that's possible.

This is something that I began to touch on in the original post. As I wrote then:

I find it helps to think of genes as biological blueprints: instructions for how to build a body (and brain). However, those instructions give rise to extremely versatile structures, that can respond appropriately to a wide range of environmental stimuli. That is, we have a huge capacity for learning.

The key thing to note here is the value of flexibility. Our brains evolved to be capable of very general/abstract reasoning and open-ended decision making, presumably because this allows us to solve a broader range of problems - a crucial skill for organisms in our particular niche. (Not so for others, however!)

This is not to say that our genes aren't important, or don't influence us. Of course they do - they're the blueprints that describe how to build these wonderful structures in the first place! But one must realise how very indirect their influence is. So long as the resultant structure as a whole facilitates genetic success, the underlying genes will be passed on. This in no way requires that our every thought be explicitly directed towards achieving evolutionary success.

As an analogy, consider the paradox of hedonism: if you try to be happy, you're sure to fail. The goal of happiness is much better served by indirect means: you should pursue friendships and hobbies (etc.) for their own sake, and happiness will likely result.

Genetic success is kind of like that. Our genes build brains that have various goals, motivations, and modes of thought. These serve as indirect means of successfully spreading the genes, even though none of our cognition is explicitly aimed towards that goal. Overall, this 'strategy' works well, as the success of our species demonstrates. But it's not perfect: although our actions tend to correlate well with genetic success, there will be some times when they end up orthogonal or even in strict opposition to the evolutionary ideal. That's the cost our genes pay for an indirect approach, but it's well worth it - otherwise we wouldn't be here!

Update: The Ethical Werewolf has more:

There's lots of things in human psychology for which an adaptationist explanation makes some sense... The capacity for laughter and the appreciation of music, however, seem more difficult for adaptationists to explain... My guess is that if you throw together a bunch of complicated, evolved modules in the brain -- language processing, emotions, auditory processing -- you get weird emergent capacities on top of those things that weren't specifically selected for.