A standard argument is that humans have evolved to the point that we don't need to cause animal suffering for our clothes and food.
In response, we state:
"Maybe some humans have evolved, but the vast majority of behavioral scientists worldwide believe that there has not been sufficient time for modern people to make significant changes in mind or body from our Paleolithic ancestors, and that in fact trying to deviate from our instinctual nature is a primary cause of mental disease. Some people can eat a vegetarian diet and stay healthy, if they carefully watch what they eat and use dietary supplements..."
"Carleton Coon, one of the most respected anthropologists of our times, has proposed that we have not yet had time to adapt from our hunting and gathering nature to the agricultural frame of mind, and the disease from the move from being hunters and gatherers to becoming an agricultural society may be a cause of violence and tension in human society..."
"The hunting instinct is bred into the bones and blood of at least most of us and is one of the most fundamental elements of human nature. Our challenge as humans is to find the best ways to express our instinctual nature. That is where ethics, values, mythology, the higher self, and spirituality come into play as guides enabling us to be healthy, happy human beings." [p. 176]
"What is the difference between humans killing animals and animals killing other animals? All animals must ultimately die, and natural deaths are not normally quick and humane. Starvation, infection, conflict, and many diseases may include long suffering before death. Some predators begin eating their prey before the downed animal is dead. Hunters kill animals quickly, sometimes instantly, and certainly as humanely as any other predator. Why is that killing an animal is so immoral for a person, and not so for a chimpanzee, a cougar, a wolf, or a shark?" [p.120-121]
James A. Swan. 1995. "In Defense of Hunting". HarperCollins Publishers, New York. ISBN 0-06-251237-4