The Alice book indirectly proves some of Darwin's theories, namely that of natural selection.  In a nutshell, Darwin explains that the survival of living things depends on their ability to adapt to their surroundings.  In fact, he says "that natural selection is daily and hourly scrutinising...the slightest variations...at the improvement of each organic being in relation to its...conditions in life" (417).  In this comment, Darwin says that nature constantly tests a being's ability to live and adapt.

The Alice books present Alice as the experimental "species" that must "[adapt] to...altered conditions" (416).  When Alice is presented with a tough and new situation, she shows a remarkably well-developed sense of natural selection.  Even without knowing it sometimes, she adapts to her surroundings in order to survive.  One instance of her not actually knowing that she is adapting is in the great hall at the beginning of Alice's Adventures in Wonderland.  After growing to an enormous height, she "sat down and began to cry" (21).  This is an understandable action; she deals with her dilemma by crying.  It is also a good way to solve her problems, even though she doesn't know it yet.  Her tears eventually make a pool that carries her out of the room when she shrinks again.

Alice's reactions to outside forces are not all subconscious.  Once she realizes that her frequent height changes can be used to her advantage, she starts making conscious decisions to survive.  For instance, after finding out that the mushroom can help her adjust her size, she "[succeeds] in bringing herself down to her usual height" (56).  Now she knows how to make herself either as large or as small as she needs to be to solve problems.

In Alice's ability to adapt to strange, difficult situations, she proves that she is fit to survive.  Darwin hypothesizes that all living things must be able to adapt to their surroundings or they will be unable to survive.  He also explains that introducing even the slightest change to any environment can severely change the way that living things think and act.  Alice shows her survivability every time she gets herself out of a mess in these books.