Passage Summary: We have five fingers because our fish ancestors did, not because five is a magic number. If we had six fingers instead, we'd probably be just as happy with them.

Conclusion: If humans had evolved from fish with six phalanges and ended up with six fingers, we would be just as satisfied with that outcome as we are with five.

Reasoning: Our five-finger structure is a result of ancestry rather than functional superiority, as five fingers are no more or less useful than other configurations like six.

Analysis: The biologist's argument rests on the idea that our current physical traits are arbitrary evolutionary leftovers rather than 'optimal' designs. To strengthen this, we need to support the claim that our contentment is based on familiarity rather than utility. Look for an answer that suggests humans generally adapt their preferences to whatever physical traits they happen to possess. If people are typically satisfied with their natural physical configurations regardless of what those configurations are, it makes the biologist's hypothetical about six fingers much more plausible.