Doug Axe, author of Undeniable: How Biology Confirms Our Intuition That Life Is Designed, tweets about “Evolution of limb development in cephalopod mollusks,” a preprint paper at bioRxiv. This is interesting: “New study suggests the genetic program for limb development predates limbs.” 

From the 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.

Where did the signaling networks come from?

Our finding that the proximodistal, dorsoventral, and anteroposterior axes of cuttlefish limb buds are patterned by the same pathways that regulate arthropod and vertebrate limb development suggests that the independent evolution of limbs in cephalopod mollusks involved recruitment of an ancient genetic program for appendage development. [Emphasis added.]

“In other words,” says Axe, “the idea came before the implementation.” That’s the way it is, universally, with creative invention.

Photo credit: Common cuttlefish (Sepia officinalis), © Hans Hillewaert.