Revisiting convergence: making teeth, shells, claws, nails (Introduction)
DAVID: Appears to have developed many times in different lines of organisms:
https://phys.org/news/2019-08-biominerals-nature-recipe-evolved.html
DAVID: Another example of God using patterns of development in managing evolution.
Or another example of intelligent cells working things out in their own way, simultaneously coming up with similar solutions to similar problems, but each with their own variations to suit their particular conditions.