Homology

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Homology
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One of the supposed proofs of Macro Evolution is
homology.
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Homologous structures are structures that are
assumed to have a common evolutionary origin.
They can be similar in function and/or
arrangement. The next slide shows an example.
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Homologous Structures
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Oram and Humer, Biology Living Systems, Glencoe,
2003 say, The commonality suggests that these
and other vertebrate animals are all related.
They probably evolved from a common ancestor that
had the same basic limb structure.
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Biggs, et.al, Biology The Dynamics of Life.
Glencoe, 2004, p.400 say,Evolutionary
biologists view such structural similarities as
evidence that organisms evolved from a common
ancestor.
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Further on these same authors say, .Structural
or functional similarity of a body feature
doesnt always mean two species are closely
related.
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Think CriticallyIs it reasonable to ask When do
structural similarities mean descent from a
common ancestor and when do they not? The next
slide shows the bones closest to the body of five
organisms that are considered homologous.
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Are These 5 Bones Homologous?
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Would you have considered these bones to be
homologous had you not been told? Are the
lengths, knobby protrusions, knobby protrusion
orientations, diameters, shape similar? What is
similar about them?
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Would you assume that they all descended from a
common ancestor? Is it reasonable to assume that
the structures all came from a similar gene?
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Homologous Structures
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Recent research reveals that just because a
structure is serving a similar purpose in
different animals it may not have come from an
identical gene.Sir Gavin deBeer, Homology An
Unsolved Problem. !971
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The fore limbs of the newt, lizard and man
develop from different parts of the
embryo.Denton, Michael, Evolution A Theory in
Crisis. 1986, p. 145-146.
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Think CriticallyIs It Reasonable To Assume That
Homology Is a Proof of Macro Evolution?
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