I first read this book a few years ago, coming to it
because I’d enjoyed Dennett’s & Hofstadter’s The Mind’s
I. Darwin’s dangerous idea has less to say
about consciousness and artificial intelligence, but covers a lot of
other very interesting ground. Its fundamental theme is the
importance of Darwin’s idea, and how it gives rise to a great many
interesting ramifications. Indeed, Dennett claims that Darwin’s was
the best idea anyone has ever had, more important than the ideas of
Newton or Einstein. For example, one reason this idea is so
important is because it explains how complexity can arise from
simple beginnings without needing to appeal to external
miracles, aliens or mystical forces. Dennett lumps all of these “explanations” together under the moniker sky-hooks, to contrast with the mundane cranes that natural selection uses.
Dennett begins with a general discussion of natural
selection and evolution as an explanation for complexity. He
also describes earlier attempts at other explanations,
including an interesting argument by Hume. He also explains
some of the many pitfalls that can trap the unwary when thinking
about evolution. For example, Lamarckianism is right out, but if you have
creatures with even a rudimentary ability to adjust their behaviour (“learn”) then you get something that looks very much like it, thanks to something called the Baldwin Effect. Another example he discusses at length is species and speciation.
Species
are not a hard and fast concept: just about any formal
characterisation one attempts (necessary or sufficient
conditions) will have exceptions. Moreover, speciation (two
species emerging from just one ancestor species) is something
that can only be detected in retrospect.
We look back and say, Ah, that’s the
point when those two populations have irrevocably split: there’s
no subsequent interaction between them.
It’s only with
knowledge about what’s to happen in the future that we can
identify speciation events.
Dennett is similarly good about Mitochondrial Eve: every
woman has one mother, and sometimes a mother has multiple
daughters. Therefore, moving back in time, from generation to
generation, there are fewer and fewer ancestral mothers (i.e., mothers with descendents now
living). Therefore, there must come a point in time when there
is just one such mother. She is our Eve, and there is nothing
special about her whatsoever. (Our Y-chromosome Adam is likely
to have been more recent, and thus a descendent of Eve’s,
because men have more sons than women have daughters.)
Dennett includes a couple of chapters about how Darwin’s idea can
be invoked to provide non-sky-hook explanations for the origins
of life, and even the universe itself. Then he moves onto showing how
a variety of scientific ideas and thinkers have come unstuck when
dealing with evolution. He singles out Stephen Jay Gould, Noam
Chomsky, Jerry Fodor, John Searle and Roger Penrose. He seems pretty
convincing on how these thinkers seek to deny Darwin’s unescapable
conclusion: complexity (life-forms, consciousness, culture) can all be
explained by a simple-minded algorithmic process. On the way he
provides some neat thought experiments. One I
particularly enjoyed was about building a robot to protect one’s
cryogenically frozen body for four hundred years so that it might be
revived in time for the arrival of the aliens. What strategies should
you adopt in the design of such a robot?
This is a very good book. Occasionally the going is a bit tough,
but the ideas within it are both fascinating and very important. So,
get out there and read it today!