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Misconceptions of Evolution Part II February 5, 2009

Posted by Ian in Science.

Another post continuing on the series I started here and Part I here.

Just one to add this time around.


3. The tree of life

I just saw this segment of an upcoming video by David Attenborough that looks very exciting (hat-tip to the rdf).  There is also this website talking about the tree of life used in that video.  We also see similar depictions in pop-culture such as the Simpsons.

This video highlights one of the major problems with the general understanding of evolution.  It mostly presents life as if it steadily progressed from bacteria through to humans and other modern day animals as a linear replacement of one creature after another.  This picture has its uses, particularly for tracing back what our ancestors were (such as what Richard Dawkins did in The Ancestors Tale). 

However this linear tree of life picture is missing the biggest part of the story from an evolutionary point of view.  There is almost nothing of the failed species along the way.  The diagram in the site linked above looks a bit like this (where A, B and C are three arbitrary modern species). 

Reality would probably look somewhat closer to this (where X represents extinct species):


This is important for a couple of reasons.  Firstly it emphasises the fact that 99+% of the species that have ever lived are now extinct.  Secondly it makes the development of complex organs far more likely (there is a much larger stage for experimentation than just one species).  Thirdly it highlights the notion that life ebbs and flows.  We get species dying off, then new opportunities arise, species fill the gaps, the gaps fill, species die off, etc.  It is a world of constant change and flux, not a steady progression from one species to the next. 

I suggest reading Stephen Jay Gould’s Wonderful Life: The Burgess Shale and the Nature of History for more information on this idea.


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