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Ileum, caecum and colon of rabbit, showing Appendix vermiformis on fully functional caecum The human vermiform appendix on the vestigial caecum. The appendix was once believed to be a vestige of a redundant organ that in ancestral species had digestive functions, much as it still does in extant species in which intestinal flora hydrolyze cellulose and similar indigestible plant materials. [10]
In humans, the vermiform appendix is sometimes called a vestigial structure as it has lost much of its ancestral digestive function.. Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. [1]
This system is used in many unrelated animals: ants, bees, and wasps, termites, naked mole-rat, Damaraland mole-rat, Synalpheus regalis shrimp, certain beetles, some gall thrips and some aphids. [189] Oxygenate blood came about in unrelated animals groups: vertebrates use iron and crustaceans and many mollusks use copper . [190]
Human trichromatic color vision had its genetic origins in this period. Catarrhines lost the vomeronasal organ (or possibly reduced it to vestigial status). Proconsul was an early genus of catarrhine primates. They had a mixture of Old World monkey and ape characteristics.
In fish, the other posterior arches contribute to the brachial skeleton, which support the gills; in tetrapods the anterior arches develop into components of the ear, tonsils, and thymus. [7] The genetic and developmental basis of pharyngeal arch development is well characterized.
Like humans, bonobos have complex social structures; they live in societies of around 100 to 120, and within that, they form smaller, tight-knit subgroups. Like humans, they bond and laugh.
Thus the zoologist Newman stated in the Scopes Trial: "There are, according to Wiedersheim, no less than 180 vestigial structures in the human body, sufficient to make of a man a veritable walking museum of antiquities." Some of the vestigial organs or organs containing evolutionary vestigial structures, as listed on the article about him: Adenoids
This arch divides into a maxillary process and a mandibular process, giving rise to structures including the bones of the lower two-thirds of the face and the jaw. The maxillary process becomes the maxilla (or upper jaw, although there are large differences among animals [11]), and palate while the mandibular process becomes the mandible or lower jaw.