Evidence for Evolution

Fossils

• Fossils provide direct evidence for evolution. They demonstrate that organisms have changed and diversified over time.
• Some fossils represent transitional forms, bearing characteristics of both existing organisms and their ancestors, demonstrating gradual change over time.
• Dating techniques, such as radiometric techniques and relativeness (layer position), can determine the age of fossils revealing the time period of the living organism, providing an evolutionary timeline.

Comparative Anatomy

• Homologous structure refers to body parts that are structurally similar in different species because they evolved from a common ancestor, like the forelimbs of humans and bats.
• Analogous structures, like the wings of bats and insects, are body parts that serve a similar function in different species but do not share a common origin, showing organisms have evolved to occupy similar habitats or ecological roles.
• Vestigial structures such as human tailbones or the wings on flightless birds, are organs or structures that have no apparent function, implying they were functional in an ancestral species and have been retained through evolution.

Comparative Embryology

• The resemblance of embryos of different species during early development stages points towards a common ancestor, an evidence of evolutionary history.

Molecular Biology

• Genetic similarities observed among various species are excellent evidence of common descent.
• DNA sequences that are more similar suggest a more recent common ancestor. For example, humans share higher sequence similarity with chimps than with mice.
• Certain markers like pseudogenes (non-functioning genes) and endogenous retroviruses (viral remnants) in DNA provide evidence of shared evolutionary history.
• Protein comparison can also be used, as different species with a common ancestor will have similar proteins.

Biogeography

• Geographic distribution provides insights into evolutionary history. Species found in one region of the world but not others often indicates they evolved in that area and haven't or couldn't migrate.
• Comparative studies of similar environments, like Australia and North America, show different groups of organisms have evolved in isolation.
• Endemic species like those on islands, which are found nowhere else on earth, suggest they evolved there and have been isolated from other populations.

Natural Selection in Action

• Direct observations of evolution in action provide concrete evidence, examples being the coloration change in peppered moths or antibiotic resistance in bacteria.
• Natural selection experiments conducted in laboratory environments also provide evidence, for example, the changes in the beak shape of Geospiza fortis (Darwin’s finch) during droughts.