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<blockquote data-quote="AbdulAlhazred" data-source="post: 9335790" data-attributes="member: 82106">Right. While my evolutionary biology education is probably only a tiny bit better than yours (I had to take college-level biology at least, and have a good working knowledge of basic biochemistry) I am fairly confident you are correct. Humans and Octopi must have shared a common ancestor something like 600 million years ago, at a stage when animals resembled worms (Ur Bilateria, the first animals with bilateral symmetry). It would be best to look at evolution from that point as basically a tree. Once two branches split, they go in different directions and over deep time become VERY different. The accumulated adaptations on each line of development are organized in different ways, arise out of different underlying parts of the biological machinery, etc. For example, Octopi have very large neurons, an adaptation for noise reduction, whereas Humans (Chordates in general I believe) have myelin insulated neurons which work somewhat differently and are much smaller, an adaptation which is also present for noise reduction. Same problem, 2 different solutions, and each solution leads to further differences. Humans have a single large brain filled with densely packed neurons. Octopi have distributed brains, a completely different architecture. There's no intermediate form that is possible. Even where we share traits in our nervous systems, basic neuronal biochemistry is pretty similar, each system has tweaked these basic ancestral traits and optimized them in different ways. While Octopi might have a form of dopamine, for example, it wouldn't work right in humans!</blockquote>

[QUOTE="AbdulAlhazred, post: 9335790, member: 82106"] Right. While my evolutionary biology education is probably only a tiny bit better than yours (I had to take college-level biology at least, and have a good working knowledge of basic biochemistry) I am fairly confident you are correct. Humans and Octopi must have shared a common ancestor something like 600 million years ago, at a stage when animals resembled worms (Ur Bilateria, the first animals with bilateral symmetry). It would be best to look at evolution from that point as basically a tree. Once two branches split, they go in different directions and over deep time become VERY different. The accumulated adaptations on each line of development are organized in different ways, arise out of different underlying parts of the biological machinery, etc. For example, Octopi have very large neurons, an adaptation for noise reduction, whereas Humans (Chordates in general I believe) have myelin insulated neurons which work somewhat differently and are much smaller, an adaptation which is also present for noise reduction. Same problem, 2 different solutions, and each solution leads to further differences. Humans have a single large brain filled with densely packed neurons. Octopi have distributed brains, a completely different architecture. There's no intermediate form that is possible. Even where we share traits in our nervous systems, basic neuronal biochemistry is pretty similar, each system has tweaked these basic ancestral traits and optimized them in different ways. While Octopi might have a form of dopamine, for example, it wouldn't work right in humans! [/QUOTE]

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