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Researchers: Program for limb development may have been in “in the bilaterian common ancestor”


What? Doug Axe draws attention to a new paper at Evolution News and Science Today which suggests that “the genetic program for limb development predates limbs.”

Abstract: Cephalopod mollusks evolved numerous anatomical innovations, including specialized arms and tentacles, but little is known about the developmental mechanisms underlying the evolution of cephalopod limbs. Here we report that all three axes of cuttlefish limbs are patterned by the same signaling networks that act in vertebrates and arthropods, although they evolved limbs independently. In cuttlefish limb buds, Hedgehog is expressed anteriorly. Posterior transplantation of Hedgehog-expressing cells induced mirror-image limb duplications. Bmp and Wnt signaling, which establishes dorsoventral polarity in vertebrate and arthropod limbs, is similarly polarized in cuttlefish. Inhibition of the dorsal Bmp signal caused ectopic expression of Notum, a ventral sucker field marker, and development of ectopic suckers. Cuttlefish limbs also show proximodistally regionalized expression of Htx, Exd, Dll, Dac, Sp8, and Wnt genes, which delineate arm and tentacle sucker fields. These results suggest that cephalopod limbs evolved by parallel activation of an ancient developmental genetic program that was present in the bilaterian common ancestor – Oscar A. Tarazona, Davys H. Lopez, Leslie A Slota, Martin J. Cohn, Evolution of limb development in cephalopod mollusks, doi: https://doi.org/10.1101/379735 More.

Is this evolution as an unfolding program?

The paper is open access.

Where have we heard this kind of thing before? Oh, earlier today! Algae have genes otherwise known only in land plants.

A friend comments, If you had asked a 1980s-era evolutionary biologist if cephalopod, arthropod, and vertebrate limbs would all use the same developmental regulatory elements, you’d have been told, certainly not! They are “classically non-homologous structures.”

Background noise: Lecterns splintering in the distance.

Doug Axe is the author of a href=”https://www.amazon.com/Undeniable-Biology-Confirms-Intuition-Designed/dp/0062349589″ target=”another”>Undeniable.

See also: Did algae trigger complex cells before 650 million years ago?

Algae already possessed genes for land, while in water (2015)

Did algae trigger complex cells before 650 million years ago?

Algae already possessed genes for land, while in water (2015)


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