TudorGothicSerpent
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- Nov 15, 2015
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Please give me your foremost and strongest direct evidence that an invertebrate grew a backbone and became a vertebrate.
The absolute strongest evidence is fairly complicated genetic information. Right now, in every cell of your body, you have genetic information that's identical to animals who don't have a spine. Some of it is information that your cells don't use at all anymore, that isn't there for any logical reason. Some of it is junk DNA (or, at least, DNA that has incredibly limited use in your body) that matches the genetic information of animals so primitive that you wouldn't even think about their relationship to you. Some of it, on the other hand, is DNA that your body still uses for the same reason as your incredibly primitive ancestors.
Other than that? The genetic and fossil evidence both suggest that there are animals that developed a notochord (a structure still preserved in fetal vertebrates and in adult examples of basal chordates) and then a true spinal column. There are living "transitional" organisms between primitive invertebrates and modern vertebrates. This animal, a lancelet, is a good example of a chordate that retains basal features from a time prior to the development of vertebrae.
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