For their opening night at the Joyce Theater, Keigwin + Company presented four dances.  Natural Selection was the ins and outs of three pairs of dancers in muted colors suggestive of simplicity and nature that didn’t add anything to similar modern pas de deux variations, and the dancers sometimes searched for their footing when set down from a lift.  One learned fast to keep ones eyes on Liz Riga, a tall, long legged, extremely flexible and vibrant dancer.