1. Anatomical proof of evolution and fossils
With all of the technology available to scientists today, there are many ways to support the
Theory of Evolution with evidence: DNA similarities between species, knowledge of
developmental biology and other evidence for microevolution is abundant.
However, scientists haven't always had the capabilities to examine these types of evidence. So
how did they support the Theory before these discoveries?
The main way scientists have supported the Theory of Evolution throughout history is by using
anatomical similarities between organisms. Showing how body parts of one species resemble
the body parts of another species, as well as accumulating adaptations until structures
become more similar. Of course, there is always finding traces of long extinct organisms that
can also give a good picture of how a species changed over time.
Early fossil discoveries
In the 17th century, Nicholas Steno shook the world of science, noting the similarity between
shark teeth and the rocks commonly known as "tongue stones." This was our first
understanding that fossils were a record of past life.
Each new fossil contains additional clues that increase our understanding of life's history and
help us to answer questions about their evolutionary story. There are two ways of analyzing
fossils:
Indication of interactions
This ammonite fossil (see powerpoint) has holes that some scientists have interpreted as the
bite mark of a mosasaur, a type of predatory marine reptile (photo) that lived at the same time
as the ammonite. The marks on the ammonite have relationship to the shapes and capabilities
of mosasaur teeth and jaws. Others have argued that the holes were created by limpets
(photo) that attached to the ammonite. Researchers examine ammonite fossils, as well as
mosasaur fossils and the behaviors of limpets, in order to explore these hypotheses.
Clues at the cellular level (photo)
Fossils can tell us about growth patterns in ancient animals. The picture at right is a crosssection through a thigh bone of the dinosaur Maiasaura. The white spaces show that there
were lots of blood vessels running through the bone, which indicates that it was a fast-growing
bone. The black wavy horizontal line in mid-picture is a growth line, reflecting a seasonal pause
in the animal's growth.
However we can not only determinate evolution by locking at fossils. When we look around us
or when we look at our body; we can determinate evolution by analyzing the anatomical
structures. They can be:
ANALOGOUS STRUCTURES: Are formed through the adaptation of living things to the
environment although they are not very close related on the phylogenetic tree of life. Such as
for example dolphins and sharks have a similar analogous structure because they live in the
same environment although dolphins are much more related with humans than with sharks.

2. HOMOLOGOUS STRUCTURES: Are the structures that permit us to see from where comes the
living thing, I mean the common ancestor. Like this we can see similarities in the structure of
bones. For example in a dolphin we find that the flipper is very similar in composition to the
human arm so we can deduce that they could have a common ancestor although they have
adapted in different ways to the environment creating analogous structures.
Homologous structures permit us to classify organisms in the phylogenetic tree which is a
branching diagram showing the relationships among various biological species based upon
similarities and differences in their physical or genetic characteristics. So they have descended
from a common ancestor.
VESTIGIAL STRUCTURES: Another way of seeing how an animal has evolved is through vestigial
structures which are leftovers from the specie before it evolved. I mean they are parts that
nowadays the individual does not use. For example humans have a tail bone that is not used as
no tail is connected to it or for example the appendix can be removed as it has no apparent
function.