Convergent Evolution and the AAT/H
The Concept of Convergence in Evolution
The AAT/H relies heavily on an important
and quite valid evolutionary principle: the principle of convergent evolution.
That said, it must also be recognized that the principle of convergent
evolution as used in the AAT/H ignores a vital element of that principle.
Therefore an explanation of this principle is in order:
Paleontology and Evolution 1988, by Robert L. Carroll (W.H. Freeman
and Company: New York) pg. 7:
"characters that are
similar in structure and function but have arisen separately rather than
from a common ancestor are termed
And he uses G.G. Simpson's description
of the terms "convergence" and the similar term "parallelism":
"Convergence is the
development of similar characters separately in two or more lineages without
a common ancestry pertinent to the similarity. Parallelism is the development
of similar characters separately in two or more lineages of common ancestry
on the basis of, or channeled by, characteristics of that ancestry."
Convergence in evolution (unrelated
living things sharing similar traits which they don't share with a common
ancestor) is due to a similarity in function in these traits.
These are often due, as the AAT/H suggests, to these living things (we'll just
consider animals here) living in similar environments which are different
from their close relatives.
There are classic examples which
are often cited, for instance arctic mammals and birds, which often have
white coats of fur or feathers, and in the case of mammals, smaller ears
to conserve heat.
(Conversely, similar animals which live in extremely
hot areas often have large ears to radiate heat -- note the difference
between arctic foxes and fennec foxes in ear size.)
which creates convergent features is an aquatic one, but unfortunately
for the AAT/H, humans share none (!) of the aquatic traits actually due to
convergent evolution (take a look at the list in the first 5 "Relevant
Questions for the Aquatic Ape Theory").
The essential part of the principle
which the AAT/H shies from is that these convergent characters are similar
in function as well as in structure. Their similarity in
function is what creates selection pressure for similarity in form, so
examining and explaining this similarity in function is critical to the
application of the principle of convergent evolution. Perhaps many of the
oft-repeated errors by AAT/H proponents arise because they typically present
examples of alleged similarity in structure without any examination of
(Of course when they also present features which aren't
similar they compound their errors.)
Why do they make these errors
about convergent evolution?
I'm not entirely sure, but part of it
seems to be a simple lack of understanding of basic evolutionary concepts.
It stands to reason that if you're putting together a theory about human
evolution, you would learn the basic concepts of evolution (and physiology
and other related studies).
It's not easy, certainly, but it's not that hard.
And it's necessary.