Human activities with regard to animals and their implications (and why we should stop them) 

Animal testing 

Dogs smoking cigarettes, cats with electrodes in their heads, mice and frogs dissected in classrooms, etc: tens of millions of animals ranging from mice and rats to monkeys are sacrificed ("sacrificed" being researcher speak for "killed") every year for the sake of experiments. https://speakingofresearch.com/facts/animal-research-statistics/ 

Animals are used to test medicines, cosmetics, household products and other chemicals. They are also used as test subjects for training in surgery and biology classes in schools. I thought that it would be simple to write this page condemning the use of animals in experiments because animals in labs are kept in much worse conditions than those kept in zoos, circuses and marine parks. In the USA, for example, animals used in experiments are excluded from the Animal Welfare Act, so they can be kept in small cages in a non-stimulating environment and be subjected to painful or even fatal tests. If, like me, you believe that animals are sentient, that is reason enough to ban experiments on animals. However, I thought that you, dear reader, deserved a more in depth discussion than a simple "No" in the style of Ricky Gervais: ""Dear intelligent people of the world, don’t get shampoo in your eyes. It really stings. There. Done. Now f@#+ing stop torturing animals."

So I've divided animal testing into two main areas: pharmaceutical/educational and commercial. Now I'm going to look at whether they are useful for society and morally justifiable.
Let's start with commercial testing... Two of the most outrageous abuses of animals for commercial reasons are tests on animals by tobacco companies in order to make tobacco products more addictive and, as alluded to by Mr. Gervais, testing of the chemicals in shampoos at high concentrations on rabbits' eyes.
In my opinion, neither of these pass the useful for society/morally,  justifiable test. Of course, I've chosen two extreme examples, but what really is the justification for testing cosmetics and beauty products on animals in concentrations that will never occur in real life? Why not just test the product in small concentrations on people directly and increase the concentration gradually until it has the desired effect or until it starts to cause harm? And just how relevant are these tests on animals to human beings? Don't forget that laboratory animals are kept in atrocious conditions whether or not they are being used as test subjects, so there is already a considerable cost that any benefits from the tests should outweigh.

Another test, the so-called LD 50 (Lethal Dose 50%) test used to be common. In this test, as the name suggests, animals are subjected to ever increasing doses of a substance until half of them die from it. Really, that's just mind boggling. What practical real world purpose does it serve?  We only need to know that a chemical is harmful, we don't need to know that it's lethal before we take precautions. Luckily it is now accepted that the results of the LD 50 test are unreliable because animals don't respond in the same way as humans, so it is being phased out. Unfortunately, it's for purely pragmatic reasons, rather than any real concerns for animal welfare.

I've concluded that testing on animals for commercial products is definitely not morally justified. I also don't believe that it is really useful. There are many alternatives to testing on animals available: “organs-on-chips”, cell cultures that respond like human skin, computer modelling to simulate human biological systems, human-patient simulators... You can find a more exhaustive list here: http://www.piscltd.org.uk/alternatives-approved-by-regulators/ In addition, the results of experiments on animals can only be a guide to the effects on humans: at some stage there will be tests on humans. These will probably start with micro-doses and then ever increasing quantities as long as no harm is caused. Why not just cut out the animal testing stage and save time and money? It should also be noted that even humans respond differently to chemicals and that what is safe for one person may have unforeseen negative effects on another.
So what about pharmaceutical/education purposes? Advocates for testing on animals often claim that advances in modern medicine have mainly been due directly or indirectly to the use of animals for tests. Although this sounds convincing, it is actually difficult to find any proof that it is true. In fact, it is possible that testing on animals has delayed the introduction of new medicines and procedures. This is because animal experiments take a long time and they cost a lot of money. And even if animal tests are successful, tests on humans are still needed before approval for a new drug or procedure is given.

Suppose that the years of animal testing were forgone
and tests were carried out on human subjects, once the medicine or procedure had successfully undergone testing using other methods, that could lead to successful treatments being available much sooner, so potentially saving more lives than those risked during the experimental phase. In addition, as animal testing is expensive, it is also a barrier to new companies entering the pharmaceutical market: this is an advantage for the existing large companies who face less competition as a result. These companies also use the expense of testing as an excuse for selling their products at, sometimes, ridiculously or perhaps even immorally high prices.

I looked at sites that were in favour of animal testing. It soon became clear to me that those in favour did not concern themselves with the question of animal sentience and so did not consider the morality of experiments on sentient creatures. It's obvious that if you consider animals to be sentient then it would be morally wrong to use them for experiments without their informed consent. If you're doing experiments on animals that are only concerned with physical reactions such as toxicity and sensitivity to light etc then the question of animal sentience has no direct relevance to the outcome of the experiment and can be ignored. As long as animals show the same or similar reactions as human beings it is claimed that the results of the experiment can be useful. 
However, what about experiments on animals for drugs treating depression, anxiety, stress etc? You would have thought that if animals are useful as test subjects for these drugs it would show that they are sentient, therefore it would be immoral to use them in experiments. On the other hand if animals cannot feel these emotions, because they are not sentient, then the experiments wouldn't be useful, would they? So how do researchers cope with this contradiction? Simple: in the scientific literature of the researchers you find that animals don't experience depression, anxiety, stress etc. What they do is show anxiety-like, depression-like and stress-like behaviour. Voilà, that's how to rationalise carrying out tests on sentient animals. 
If, on the other hand, we take a rational look at these so called "-like" behaviours, we see that it is just another manifestation of human exceptionalism. We know that different drugs can treat depression by different means. For example, some work by balancing different neurotransmitters and, prior to being approved for use by humans, they were tested on animals. It is clear that humans and the test animals must have inherited some traits from an earlier common ancestor for these drugs to be effective.  It seems rather extraordinary to claim that it is only in humans that these traits actually cause depression, while in animals they just produce depression-like behaviour. According to the theory of evolution, traits that confer better survivability have a greater chance of being passed on. Did evolution create all those metabolic pathways and neurological structures in many different species just so that finally many millions of years later humans could benefit from them, but no other species? It's possible that I'm missing some information or that my logic is wrong (in which case please get in touch via nala85480@hotmail.com) but it seems to me that the simplest explanation is that these traits do produce depression, anxiety or stress not just depression-like, anxiety-like or stress-like behaviour. Therefore, those animals must be sentient.

In conclusion, I believe that for pharmaceutical/education purposes,  animals testing is morally wrong as they are sentient creatures who have not given their informed consent. I'm also not convinced of the usefulness because of the differences between animals and humans, the cost and the delay that it causes.