In the 14.2 issue of Skeptic Michael Shermer and David Zeigler had a couple of articles on the evolution of intelligent alien life. I sent a letter to the magazine pointing out some problems with their arguments but it seems that the letter did not make it into the next issue. I am, therefore, putting up a copy of the letter here:
In their articles on the likelihood of the evolution of human-level intelligence, David Zeigler and Michael Schermer fail to consistently distinguish between two very different claims. The claim they mean to be looking into is something like how probable it is that evolutionary processes should lead to highly intelligent organisms. However, all too often, both authors confuse this general question with the issue of how likely is it that evolutionary processes should lead to a particular intelligent life-form – humans. The heart of the problem lies in determining what we mean when we talk about ‘human-level intelligence’.
Something of the difficulty can be seen when Zeigler compares human-level intelligence with such adaptations as the narwhal’s tusk. Both, he claims, are singular traits. And, in a way, he’s quite right. Human intelligence, with all of its quirks and peculiarities, with the particular ways it makes use of pre-existing traits and finds work-arounds for existing limitations, is definitely singular, just as the narwhal’s tusk. But, if he wishes to talk about advanced intelligence in general (understood broadly enough to include humans!) he surely shouldn’t be comparing it to the narwhal’s tusk but, perhaps, to the appearance of sharp defensive growths on the head. And these are hardly a singular trait: narwhals, rhinocerii, elephants, goats, boars, deer, some lizards and a great variety of insects are among the many different species that have them. To use another example, advanced intelligence (as opposed to specifically human intelligence) would seem to be more like flight, than like the particular different anatomical structures by which flight is achieved by insects, bats and birds.
Much the same error is made by Schermer when he quotes Alfred Russel Wallace on how unlikely it would be for humans to evolve twice. Humans, yes: advanced intelligence is a very different question, however. Any intelligent aliens will not just look very different from us. They will think different, too. The problem is how to characterise advanced intelligence without relying too much upon the one example we have available. After all, must all intelligent life-forms have technology, complex societies, culture or language? Good arguments can be made for each of these traits but we can hardly be sure given the paucity of empirical evidence. In that situation it is hardly surprising that we should fall back too much upon the human model. Still, it is important to try to distinguish the two: the likelihood of humans evolving twice is clearly close to zero, the likelihood of advanced intelligence evolving again is a much more difficult question.
One of the “relatively secure predictions that one could make about life on a distant planet” that Zeigler makes is that “genetic selfishness will prevail”. Yet, Richard Dawkins’ view that evolution only takes place on the genetic level is but one end of a spectrum of evolutionary views and the likelihood of the appearance of advanced intelligence looks very different depending on where one stands on that spectrum. For example, one can see evolutionary selection as taking place on a number of levels (genetic, individual, social, etc.) with ‘major transitions in evolution’ (Maynard-Smith and Szathmáry 1995) occurring when a new level of organisation becomes stable enough for selection to become significant on that level: group selection is one example. Looking at this macroevolutionary scale, it seems that such major transitions standardly allow for evolutionary processes to occur at a faster rate – cultural evolution being like switching into top gear. If advanced intelligence is linked to rapidly evolving culture, as seem likely, it may be that there is a macroevolutionary argument for the evolution of such intelligence wherever life has had enough time to build up speed by going through the major transitions. If this is correct, it should not be surprising that such large-brained animals as whales or elephants have not made much progress toward advanced intelligence. They have not crossed the threshold of the major transition characterised by complex culture that allows for much faster change. One or two million years ago human ancestors were not all that different in their behaviour from other animals: and that’s just a moment compared to the 3.5 billion years of life on Earth. Who knows what the descendants of elephants or dolphins could achieve in a million years if they managed this major transition?
Just Another Deisidaimon 
Posted on December 1, 2008
0