Deductive Reasoning to Understand the Past

Deductive Reasoning to Understand the Past

Deductive reasoning combines the use of evidence and theories to make deductions about the past. Therefore scientists use their understanding of continental drift and natural selection theories, together with evidence of climate changes and extinct organisms from the fossil record, to piece together Earth's history.

• Scientists use the fossil record to make conclusions about the history of life through a process of deductive reasoning.
• Deductive reasoning involves combining our understanding of known principles to make conclusions about new evidence that we have uncovered.
• Our knowledge of the history of life is not based on radiometric dating methods alone. Rather, our understanding of the changes in Earth's climate and biogeography allow us to make conclusions about newly discovered fossil evidence.
• For example, from our knowledge of the changes to the Earth's early atmosphere, we know that the formation of the ozone layer blocked off the damaging rays of the sun's UV rays. This led to the growth of plant species which gradually made terrestrial existence possible.

• A transitional fossil is any fossilised remains that is common to an ancestral life form as well as to the group that is derived from it.

• Transitional fossils give us information about how an ancestral species evolved to form the existing species.

• An example of a transitional fossil is the Archaeopteryx. It is thought to belong to the genus of Theropod dinosaur which is closely related to the birds.

Comparing the skeleton of a modern bird (chicken) to the Archaeopteryx

We will use the pictures below to compare the skeletons of a dinosaur (Theropod), Archaeopteryx and a chicken (modern bird).

Skeleton of a dinosaur (Theropod)

Skeleton of Archaeopteryx

Skeleton of a chicken (modern bird)