Genetic Struggle

by Ian Tullis
Answer: EVOLVE

This puzzle first determines an evolutionary tree (one ancestral species becoming sixty-four new species) and then collapses the tree (those sixty-four battle down to one).

The initial letters of the animal names, in the order given, spell out OUR PHYLOGENETIC TREE IS THE BATTLEGROUND UPON WHICH WE STRUGGLE TO SURVIVE. Phylogenetic (evolutionary) trees are constructed using differences and similarities in DNA sequences. There are various methods for doing this, but in this very simple case, there are no ambiguities and all methods should yield the same result: a binary tree. Any phylogenetics software will spit this out right away, but it's also possible to construct the tree by hand. Using only the first seven positions as an example:

• Position 1: Paper Giraffe has a unique T.
• Position 2: Scissors Lynx has a unique G.
• Position 3: Paper Giraffe and Scissors Lynx share A; everything else has T.
• Position 4: Rock Rook has a unique C.
• Position 5: Scissors Rat has a unique T.
• Position 6: Rock Rook and Scissors Rat share G; everything else has C.
• Position 7: Paper Giraffe, Scissors Lynx, Rock Rook, and Scissors Rat share A; everything else has T.

etc.

This data tells us the following.

• Position 1: (nothing - each of the 64 species has one unique difference like this, just to make its sequence unique.)
• Position 2: nothing
• Position 3: Paper Giraffe and Scissors Lynx seem to be more closely related to each other than either is to any of the other 62 species. They should form a group.
• Position 4: nothing
• Position 5: nothing
• Position 6: Rock Rook and Scissors Rat should form a group.
• Position 7: Paper Giraffe, Scissors Lynx, Rock Rook, and Scissors Rat should form a group.

The simplest tree that satisfies all of these is:

-Paper Giraffe-\
                >-\
-Scissors Lynx-/   \
                    >---
-Rock Rook-----\   /
                >-/
-Scissors Rat--/

Going on in this way, a binary tree emerges. Depending on how the solver constructs the tree, it may look superficially different, but the underlying topology should always be the same.

Once the tree is created, it looks like a tournament bracket, and the Rock/Paper/Scissors animals happen to be paired up such that there are never any ties and the tournament can be completed.

The winner of the tournament is the Rock Stork. There is no good reason to call this in as the answer, since this is the Rock Stork's puzzle. The answer lies in the six opponents that the Rock Stork personally defeated along the way. The initial letters of their (animal) names spell out EVOLVE.