There are countless examples of adaptation under duress. The only reasonable conclusion that might be drawn from these is that evolution can be purposeful: a concept cogently encapsulated in the word adaptation.
Blind Cave Fish
The Mexican tetra is a small, hardy, freshwater fish, native to rivers in Texas and eastern Mexico. Those that live in caves have lost their sight. Being able to see is energetically expensive. Nature favors economy.
The Mexican tetra went blind without any genetic mutation. Instead, the genes responsible for developing eyes and sight were silenced via methylation, an epigenetic technique. This is an explicitly directed, exquisitely thrifty adaptation.
“Epigenetic processes can play an important role in adaptive evolution.” ~ American developmental biologist Brent Weinstein et al