Spare the chimps, boil the shrimps, shock the mice, kill the lice, eat the hogs, pith the frogs, blind the rabbits, what drives these habits?

One hundred and fifty years ago Charles Darwin published his classic book On the Origin of Species. This book is considered by many to be one of the most influential works ever published. There and elsewhere Darwin emphasized that differences among species are differences in degree rather than kind, and his ideas about evolutionary continuity revolutionized the ways in which we think about who "we" (humans) are and who "they" (other animals) are

Human animals use nonhuman animals (hereafter animals) in many ways - for food, research, , entertainment, and testing cosmetics and other products. Animals are also routinely and wantonly killed because humans want to expand their horizons - building more shopping malls, parking lots, subdivisions or office buildings. Human benefits are said to outweigh the costs to the animals - their , pain, and death -- and human interests trump those of the animals.

People often use species membership to decide which animals can be used for various purposes. Using species membership for such decisions rather than an individual's unique characteristics is called "speciesism", a term coined by the psychologist Richard Ryder to indicate prejudice based on physical differences.

The Oxford English Dictionary defines speciesism as " against or exploitation of certain animal species by human beings, based on an assumption of mankind’s superiority." For example, all and only humans might constitute a protected group regardless of an individual's unique characteristics. When animals such as great apes are protected from invasive research this decision is speciesist because all great apes are protected regardless of an individual's unique characteristics. Speciesism results in animals being classified hierarchically as “lower” and “higher” with humans on the top rung of the ladder. This speciesist view ignores individual variations in behavior within and between species and hierarchical speciesism results in endless harm and is bad biology.

Speciesists often use taxonomic or behavioral (cognitive, emotional) closeness to humans, similar appearance, or the possession of various cognitive capacities displayed by normal adult humans to draw the line that separates humans from other animals. Cognitive abilities include the capacities for self-consciousness, to engage in purposive behavior, to communicate using a language, to make moral judgments, and to reason (rationality).

Using these criteria, many animals cannot qualify for protection. But there also are some humans (young infants and adults whose lives are compromised physically or psychologically) who cannot qualify either, and this can be a problem for speciesists who rely on species-typical cognitive or emotional capacities and ignore individual differences.

Because of individual differences within a species, this view from the top, a human-centered "them" versus "us" perspective, can be difficult to apply consistently. Speciesists also often use such words as "higher" and "lower" to refer to different groups of animals. But, such words fail to consider the lives and the worlds of the animals themselves. Value judgments also accompany words like "lower" and "higher" and can result in mistreating individuals who are thought to be lower - not as smart, emotional, good, or valuable - than others based on species membership.

While there are obvious species and individual differences in behavior, in and of themselves they mean little for arguments about animal protection. Many animals experience pain, anxiety, and suffering (physically and psychologically) when they are held in captivity or subjected to extreme starvation, , physical restraint, or presented with painful situations from which they cannot escape. And even if it's not the same sort of pain, anxiety, or suffering experienced by humans, or even other animals including members of the same species, their feelings count. "Anyone who says that life matters less to animals than it does to us has not held in his hands an animal fighting for its life. The whole of the being of the animal is thrown into that fight, without reserve." (Elizabeth Costello, in J. M. Coetzee's book The Lives of Animals)

It’s individuals who count when we consider how we treat other animals. Philosopher James Rachels’s important notion of moral individualism that he presented in his book Created from Animals: The Moral Implications of Darwinism is based on the following argument “If A is to be treated differently from B, the justification must be in terms of A’s individual characteristics and B’s individual characteristics. Treating them differently cannot be justified by pointing out that one or the other is a member of some preferred group, not even the ‘group’ of human beings.” According to this view, careful must be paid to individual variations in behavior within species. It is individuals who personally feel pain and suffer, not species.

Those people who choose use animals must show more sensitivity to the animals they use. Animals aren't mere resources or property. We must respect their dignity and their lives. It's a privilege to share their worlds.

Much animal use is driven by the similarities rather than the differences between humans and other animals. Philosopher Lynne Sharpe points out in her book Creatures Like Us that when we explore and ponder the similarities and differences among animals it all depends on how we define ourselves. She writes, “Those who define ‘us’ by our ability to introspect give a distorted view of what is important to and about human beings and ignore the fact that many creatures are like us in more significant ways in that we all share the vulnerability, the pains, the fears, and the joys that are the life of social animals."

If "them" who are used are so much like "us," much more work needs to be done to justify our choices of how to use animals for human ends. Speciesism fails to provide a strong defense.