The saying "you can't make a silk purse out of a sow's ear" means that the person cannot accomplish a goal with the materials on hand. The phrase indicates futility, hopelessness and impossibility.
The saying comes from the book "Ephemerides," which was published in 1579 by Stephen Gosson. Making a silk purse out of a pig's ear is an old-fashioned, hyperbolic example of an impossible task. The saying was proven literally false by scientists in Massachusetts in 1921 when a team of chemists from Arthur D. Little, Inc. created a filtering process that allowed them to spin thin silk threads from processed pig ears. Their method was expensive and impractical, and it served no useful purpose other than contradicting Gosson's saying.