Originally posted by lee_merrill
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Originally posted by lee_merrill
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Look, phylogenetic groups are defined by having members all or mostly share certain features. Arthropods, for example, are defined as having multiple appendages, segmented bodies, etc. Some of these presently shared features will be present in fossil arthropods, going back to the first arthropods near the origin of the group - that's how those first arthropods are defined as arthropods, after all. A subset of them will also be present in the non-arthropod ancestors that gave rise to the arthropods.
For those reasons, you should expect at least some of the features of modern phylogenetic groups to be present not only in their earliest members, but also in the ancestors of the earliest members.
(There are complications like features that are present in all early and some present members, but lost in other members, but we can set that aside for now.)
This work suggests that the structure of the insect brain may be one of those things that can be traced back to the earliest arthropods, and perhaps even to their ancestors. Given that this is precisely the behavior we'd expect in a phylogenetic group, why do you call it a problem?
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