Tissue origins of the mouse interparietal complex. The interparietal complex has two origins: The medial proportion stems from the neural crest and the lateral part the mesoderm. The dual tissue origin of the interparietal can be traced back to the evolutionary fusion of the medial interparietal to the tabular bone in mammalian lineages. (Picture: UZH) Another result that also refutes previous assumptions concerns the origin of the bone. As Koyabu reports: "Whilst it was previously assumed that the mammalian interparietal was composed of two elements, we discovered that it develops from four elements: a medial and a lateral pair." The tabular bones of our reptile-like ancestors and fish correspond to the lateral interparietal bones, which were overlooked until now. According to the new results, however, they have survived in mammalian lineages after all.--
2+2 does not necessarily equal 1 or 4. They assume that one bone diverged into 4 bones, or 2 bones, or bones in different part of the head, and that they are the same. However, the one thing that people seem to forget is that the genetic blueprints have to work at every stage of development. A species that had half formed or malformed bones in their skull would have had a greatly reduced chance for survival and reproduction.

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What is the purpose of living? How about, 'to reduce needless suffering. It seems to me to be a worthy purpose.