Evidence for Evolution

Fossil Record

The fossil record provides a collection of all the known fossils.
Fossils of earlier species show slow, gradual changes in anatomical features over millions of years which is evidence of evolution.
Fossils trapped in different layers of rock (strata) can be used to determine the relative ages of species.
Evolutionary paths can be traced through transitional fossils of extinct species that clearly demonstrate a link between ancient species and modern ones.

Comparative Anatomy

Comparative anatomy investigates the anatomical structures of different species to find evidence of common ancestry.
Homologous structures, those with a common origin but may now perform different functions (e.g., bat’s wing and human arm), suggest evolutionary relationships.
Vestigial organs are remnants of structures that had important functions in ancestors but are no longer necessary in the modern organism, confirming that characteristics change over time.

Comparative Embryology

Comparative embryology considers the similarities in the early development or embryological stages of different species.
Many species show remarkable similarities in embryonic stages, indicating a common ancestry.
For example, the presence of gill slits in human embryos provides evidence for common ancestry with fish.

Biochemistry and Genetics

Similarities in biochemical processes and genetic makeup between different species provide strong evidence for evolution.
All known living organisms use the same basic biochemical molecules like DNA, RNA, ATP and many identical enzymes, which points to a common origin of life.
DNA sequencing has shown us the degree of similarity between the DNA of different species. A closer genetic relationship suggests a more recent common ancestor.

Observations of Evolution in Action

Evolution is a slow process that usually takes thousands of years to see noticeable changes, but in organisms with short lifecycles, we can observe evolution.
Bacteria developing resistance to antibiotics is an example of natural selection and evolution happening in a relatively short period.
Darwin’s finches in the Galapagos islands are another example where different beak shapes evolved in response to differing food sources.

Understand that evolution is a gradual process that occurs over a long period. It is essential to know how different fields of biology come together to provide an overwhelming mountain of evidence for the grand scale of biological evolution.