The Skeptics' Guide to the Universe > Podcast Episodes

Podcast #38 4/12/2006

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Wonko the Sane:
That is one of the semantic issues with evolution, by naming specific species we break them into false dichotomies when in reality it is hard to name a specific point where you could say "That is a chicken but it's parents aren't"

Steven Novella:
Right - the question really has no answer because the concept of species is artificial. "Species" is just a useful place-holder, there isn't really any such thing. There is no way to definitively define where one species ends and another begins over evolutionary time. So there really was no first chicken.

Jay:
Steve, lets say we genetically defined what a modern day chicken is taking into account the variations that normally occur(color, size etc).  If we had the ability to line up all of the ancestors of the modern chicken then at some precise moment in time the very first chicken as we know them was born.  So at some point in history a modern chicken came into existence. This does not define when the so called chicken species started, but it is when the FIRST chicken came to be.  How much of a genetic variation exists between humans? At what point would we consider someone not human, when they couldn’t breed with a real human?

Paulhoff:
Yea, yea, yea, now where’s the bacon.

Paul

 :D  :D  :D

bort:

--- Quote from: "Jay" ---At what point would we consider someone not human, when they couldn’t breed with a real human?
--- End quote ---


I don't think there is any consensus on what is the true definition of a species.  The most common view is that it is this definition given by Ernst Mayr: "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups"  This is a somewhat unsatisfying rule due to the fact that not all species reproduce sexually.  Also, it doesn't really take into account species that are connected over evolutionary time but never existed at the same time.  These groups could potentially interbreed, but could never actually accomplish it (without a delorean).

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