Most Compelling Evidence of Evolution
Despite the diverse range of physical evidence, the theory of evolution still has many naysayers. Which of these facts makes the most compelling case?
DNA analysis techniques of the past 50 years have been used to establish species similarity on a base-pair level. Given two species, the degree of similarity between their DNA is closely mirrored by similarity in morphology. For example, the DNA of humans and chimps is 98% identical. Modern sequencing techniques are so advanced that family's can submit their DNA to determine which countries their great-grandparents migrated from.
Although incomplete, the fossil record holds are remarkable number of specimens, including "missing links", that show evolution at work. Studying the bones of vertibrates, paleontologists see a clear branching out of anatomical features from common ancestors. There is no exception for the human line, whose ancestry includes fossils of Ardipithecus, Homo Habilis, Homo Erectus, and Neanderthal.
Humans have been toying genetics for over 10,000 years, ever since the first animals were domesticated to assist with hunting and farm work. Modern day dogs, cattle, sheep, goats, cats, and pigs are all products of selective breeding. The wide range of dog and cat species is evidence of evolution in fast-forward. And artificial selection isn't limited to animals. Plants like corn, apples, wheat, and potatoes have been so heavily modified by selective breeding that they bare little resemblance to their counterparts just centuries ago.
Scientists studying the anatomy of modern day animals find similar structures in a variety of specialize forms. A species' bones morph to better suit whatever environment it must survive in. Completely different-looking species like humans, cats, whales, and bats all share similar skeletal features like number of digits and carpal bones. Fossil evidence of in-between ancestors shows us snapshots of these bones morphing.
As proposed by Darwin, isolated oceanic islands like Hawaii and the Galapagos present a self-contained natural selection laboratories. These small island chains have no indigenous land-mammals, with all evidence supporting the hypothesis that oceanic islands were settled accidentally by migratory species like birds and aquatic mammals. The specialization of the finch's beak throughout the Galapagos archipelago, where food sources differ from island to island, shows natural selection at work.
All vertebrates, whether fish, reptile, or mammal, share a similar embryonic development process. Each embryo starts off in an un-specialized state and develops species-specific features during pregnancy, suggesting ancient ancestry. The human embryo has a tail and gills in its early development stages before their morph into other features.
Given continental drift and plate tectonics theory, the distribution of modern-day species must coincide with ancestors on once-proximate continents. This is indeed the case. For example, paleontologists have been able to successfully predict the existence of marsupial fossils in Antarctica as would be expected given that the original marsupials found in South America could only settle Australia via connecting Antarctica.
The affects of natural selection have been well-documented in recent history. One such example is that of the peppered moth, which existed in a light and dark variety, and whose numbers changed along with levels of pollution in England during the Industrial Revolution. With low pollution, the trees on which these moths lived were light-colored, producing good camouflage, favoring light-colored moths. With high pollution, the trees were colored in dark soot, favoring dark-colored moths.
The Earth is 4.54 billion years old. This age was determined by radio-active analyzing uranium-rich samples of rocky material across the globe, including meteorites. Independent analysis of the Sun's mass and luminosity suggests that the solar system is roughly the same age as the Earth, as are most meteorites. While the Earth's old age is not evidence of evolution per se, it does show the plausibility significant genetic divergence over such timeframes.
The age-old struggle against the common cold is evidence of micro-evolution in action. A strain of flu virus is only effective when it takes on a new form to which hosts have yet to develop an immunity. As soon as an immunity develops, the virus is suppressed until new mutations lead to a new strain. Given their short life-cycles, viruses and bacteria churn through generations quickly, allowing mutations to accumulate many times faster than they do in animal or plant species.
- This list covers broad types of evidence for evolution.
- Don't create new entries to cite multiple examples of the same type.