What is homology evidence?
Homology evidence is a type of evidence for evolution that shows how different organisms share common ancestry and inherited traits from a distant ancestor. Homologous structures are physical features that have the same basic structure and origin, but may have different functions in different organisms. For example, the forelimbs of humans, bats, deer, and dolphins are homologous structures because they all have the same bones and muscles arranged in a similar way, but they perform different functions such as grasping, flying, running, and swimming.
How does homology evidence support evolution?
Homology evidence supports evolution by showing how natural selection and adaptation can modify the inherited structures of organisms to fit different environments and lifestyles. For instance, the forelimbs of bats and birds have evolved into wings for flight, while the forelimbs of whales and seals have evolved into flippers for swimming. These modifications are the result of changes in the size, shape, and position of the bones and muscles over many generations. However, the underlying structure and origin of the forelimbs remain the same, indicating a common ancestor that had forelimbs.
How do scientists study homology evidence?
Scientists study homology evidence by comparing the anatomy, embryology, and molecular biology of different organisms. By examining the bones, joints, and muscles of the forelimbs of various vertebrates, scientists can reconstruct how they functioned and how they changed over time. By observing the development of the forelimbs in embryos, scientists can identify the genes and signals that control their formation and differentiation. By analyzing the DNA and proteins of the forelimbs, scientists can measure the degree of similarity and divergence among different species.
One example of a scientific study that used homology evidence to understand the evolution of vertebrate forelimbs is by Molnar et al. (2021). They used three-dimensional digital models of the fins and limbs of two extinct early tetrapods (Pederpes and Acanthostega) and a closely related fossil fish (Eusthenopteron) to reveal how function of the forelimb changed as fins evolved into limbs. They discovered three distinct functional stages in the transition from fins to limbs, and that these early tetrapods had a very unique pattern of muscle leverage that did not look like a fish fin or modern tetrapod limbs.
In conclusion, in evolution, the study of vertebrate forelimbs is related to homology evidence because it shows how different organisms share common ancestry and inherited traits from a distant ancestor that had forelimbs. Homology evidence supports evolution by showing how natural selection and adaptation can modify the inherited structures of organisms to fit different environments and lifestyles. Scientists study homology evidence by comparing the anatomy, embryology, and molecular biology of different organisms.