[9] In the beginning, the term "animal ethics" was associated solely with cruelty, only changing in the late 20th century, when it was deemed inadequate in modern society.
Many did not support this act as it communicated that if there was human benefit resulting from the tests, the suffering of the animals was justifiable.
It was not until the establishment of the animal rights movement that people started supporting and voicing their opinions in public.
In 1635, Ireland was the first country to pass animal protection legislation, "An Act against Plowing by the Tayle, and pulling the Wooll off living Sheep".
[13] In 1789, philosopher Jeremy Bentham argued in An Introduction to the Principles of Morals and Legislation, that an animal's capacity to suffer—not their intelligence—meant that they should be granted rights: "The question is not, Can they reason?
[16] The same year, Gompertz published Moral Inquiries on the Situation of Man and of Brutes, one of the first books advocating for what will be more than a century later known as veganism.
[26][40] According to Jacy Reese Anthis, even farms considered high-welfare typically have serious welfare issues, notably due to genetic selection.
[41] Peter Singer suggests that even as a vegan, there are a few exceptions like oysters that are ethically acceptable to eat because they cannot suffer and their farming is environmentally sustainable.
[45] Studies on bees notably showed multiple markers of sentience, such as the ability to strategically avoid threats or harmful situations unless the reward is significant.
[47] In 2023, more than one trillion insects were farmed annually, with little to no formal welfare standards in place, leaving companies to determine their own practices.
[48] After them, there was also Galen, who was Greek but resided in Rome, carrying out experiments on living animals to improve on the knowledge of anatomy, physiology, pathology, and pharmacology.
[50] This ensured the testing of drugs on animals before marketing of the product, to confirm that it would have no harmful implications on humans.
[51] In addition, the deaths of these animals are considered sickening; from inhaling toxic gas, having skin burned off, getting holes drilled into their skulls.
The Three Rs were first introduced in a 1959 book called "The Principles of Humane Experimental technique" by zoologist W. M. S. Russell, and microbiologist R. L.
Secondly, the evolution of animal ethics as people started to realise that this ideology was not as simple as was first proposed.
Singer made his decision to support utilitarianism on the basis of sentience, selecting that aspect as the differential factor between human and animals; the ability of self-consciousness, autonomy and to act morally.
[56] However, critics allege that not all morally relevant beings fall under this category, for instance, some people with in a persistent vegetative state who have no awareness of themselves or their surroundings.
[60] Based on Singer's arguments, it would be as (or more) justified to carry out experiments in medical research on these non-sentient humans than on other (sentient) animals.
Third, utilitarianism plausibly implies that we should prioritize farmed and wild animal welfare and pursue a variety of interventions at once to make progress on these issues".
[62] This ethical theory can be implemented from conflicting sides, for example, a researcher may think it is their duty to make an animal suffer to find a cure for a disease that is affecting millions of humans, which according to deontology is morally correct.
One advantage that this theory has over the others, is that it takes into account human emotions, affecting the moral decision, which was absent in the previous two.