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"BILATERALLY SYMMETRIC embryos of echinoderms, which as adults display pentamerous radial symmetry, likewise are relics that disclose secrets of echinoderm origins. Even the possession of a head region at one end (rather than in the center) of cephalized animals is a form of historical remain: still obviously functional yet a reminder of the past, when heads first arose." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

REMNANTS. "Consider the six basic ‘diagnostic’ features of the Phylum Chordata, found in all chordates (and only chordates) at some point in their life cycle: the notochord; single, dorsal, hollow neural tube; myomeres (segmental muscle units); postanal tail; pharyngeal slits; and endostyle. In short, it is not possible to disconnect ontogenetic from phylogenetic remnants in this instance. Homologies of these jointly conserved evolutionary-developmental structures constitute another type of historical residues." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

DEFAULT NIPPLES. "Darwin perpetuated the myth that male nipples are true evolutionary vestiges that stem from lactation in male as well as female ancestral mammals. They are, however, a developmental holdover from the early, indifferent stage of embryonic development, when the milk line arises but before the embryo has developed along the default female track or divergent male pathway. Male nipples are default structures formed earlier in development than the differentiation between males and females." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

INTERTWINED. "In many cases it is not easy to disentangle the evolutionary and developmental processes that interact to produce wholesale phenotypic alteration." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

SO ENDS this excursion into Morning Glories and tulips, to be concluded next weekend. Humans have the capacity to obsess on floral beauty and the technical capacity to breed exotic varieties, to the enormous appetite of the public. Flowers are potent symbols with many meanings in many cultures. In both the Morning Glory and the tulip, mankind has collaborated with viral elements to generate these objects of obsession, at great cost and labor. And coming full circle, we now have a good handle on the biology of these flowers. View in LinkedIn

VESTIGIAL GENES. "What atavisms tell us is that what evolution has put away, development can quickly restore. Switches that turn off gene expression can turn back on, and hence these evolutionary remnants reveal the dynamic interplay between “ontogeny and phylogeny” that Gould expounded on." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

HEN'S TEETH. "Contrary to the well-known phrase, 'As rare as hens' teeth,' the researchers say they have found a naturally occurring mutant chicken called Talpid that has a complete set of ivories. The team, based at the Universities of Manchester and Wisconsin, have also managed to induce teeth growth in normal chickens -- activating genes that have lain dormant for 80 million years." https://lnkd.in/dzSQugZ View in LinkedIn

RETAINED FORMS. "A similar example comes from the origin of mammary glands as derived sweat glands. Even sexual dimorphism in body form and size can, in many lineages, represent retention of former evolutionary and developmental conditions." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

EVOLUTION-DEVELOPMENT FORCES. "The joint evo-devo changes of these structures in mammals (where they are still functional, but with a new function), as well as in extant reptiles that have also evolved from the common ancestor with mammals, provide much evidence as to joint ontogenetic and phylogenetic transformation." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn

MIDDLE EAR. "One of the best examples of such a major remnant of evolutionary and developmental history involves the mammalian middle ear ossicles (the malleus, incus, and stapes bones), all of which are derived from jaw bones of ancestral reptiles but which now play a key role in hearing by amplifying sounds." https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5 View in LinkedIn