The Debate About Anatomical Homology
If
one looked at the forelimb of a human, a bat, a pig, and a horse, one
would see that the structure is very similar, with one bone in the
upper limb and two bones in the lower limb. The study of similar
structures in creatures is called anatomical homology. There are
different areas of anatomical homology. There are similarities in
skeletons, brains, nervous systems, blood vessels, muscles, and
digestive systems. As with many other things, the evolutionists have
one view about anatomical homology, and the opponents of evolution
have a completely different view.
The
evolutionists think that there are similarities between different
species because the creatures inherited the traits from a common
ancestor, therefore pointing to common descent. The opponents of
evolution, however, think that there are similarities between
different species because a designer used a similar design. Two other
theories are that the similar body parts were designed for a similar
purpose, or that they are obeying natural laws.
The
evolutionists say that because of common descent, similar genes and
developmental pathways should produce similar structures, and
different genes and developmental pathways should produce different
structures. However, other people point out that many times, the
exact opposite is true.
In
addition, there are some similar structures that everyone agrees are
not due to common ancestry, even though they are found in different
types of organisms. The evolutionists call this convergence, and try
to explain it by saying that natural selection acting on two or more
different species produced similar structures. However, other people,
when considering convergence, say that it is extremely unlikely for
the random process of natural selection to result in many similar
complex structures.
No comments:
Post a Comment