Posts Tagged mutation
One well-known metaphor for the process of biological evolution is ‘tinkering.’ First proposed by François Jacob in 1977 in a now-famous paper in the journal Science, the idea captures two facets of evolution: the fact that new things must be developed from pre-existing things, and the apparent fact that evolution does not proceed with guidance. The picture is one of an actor mindlessly fiddling with implements, tossing them into the mix to see what happens. A believer might prefer the actor to be mindful, perhaps even goal-driven, but the process shows no evidence of this—Hume’s “stupid mechanic” seems a more apt metaphor to me. But mystical preferences aside, a view of evolution as tinkering brings a set of expectations or predictions to evolutionary thought.
One of those predictions is that innovations in evolution should be rare. More precisely, whenever something “new” appears, we expect it to be built from old stuff, from the components already there. No matter how innovative the new thing looks, we expect it to be a subtle reworking of whatever came before. Read the rest of this entry »
There are many aspects of biology that should inspire wonder in believers and non-believers alike. One of them, in my humble opinion, is the form of genetic recombination known as ‘crossing over.’ You can read a bit more about it elsewhere, but the gist is that in sexually-reproducing creatures, the formation of sperm and eggs involves a mixing-up of genetic material that ensures that the billions of individual sperm or eggs are genetically unique. The process involves the deliberate cutting of DNA, followed by a repair process that often stitches pieces together that weren’t together before. It is an amazing thing, almost audacious in its apparently deliberate drive to create genetic variation, via means that are elsewhere associated with chaos and catastrophe. (Such as cancer, to complete a nice alliterative triplet of horrors.) Read the rest of this entry »