A total of 4,121,582 animal experiments were carried out in the UK last year. To put that in perspective, the UK consumes an estimated 2.5 billion animals a year as food. That means that for every one animal used for scientific research, 606 animals are killed for meat.

Similarly, the Dog’s Trust calculated that in 2013 there were 111,986 stray dogs in the UK, 8,903 of whom were put to sleep. According to Home Office statistics, 4,779 scientific procedures were carried out on dogs in the same. This means that, for every one dog used in an experiment, approximately 23 dogs wandered the streets alone, and two dogs were put down because they didn’t have a home to go to.

I think it’s reasonable, given those figures, to suggest that animal testing is not the most pressing cause of preventable animal suffering in the UK (not to mention the way we treat foxes and badgers). But is it justified on scientific grounds?

It has been argued by various animal rights organisations (with some notable exceptions) that animal testing is unhelpful and misleading, and as such is of no use in human medicine. However, medical advances from areas as disparate as blood transfusions, vaccines and MRI scanning would have been impossible without animal experimentation, and animal research has taught us innumerable things about living systems.

These were: toxicology (375,010), immunology (578,400), cancer research (501,400), physiology (472,200), anatomy (458,000), genetics (449,900), molecular biology (197,094), pharmaceutical R&D (239,730), and other, including psychology, pathology, nutrition and zoology (848,266). (source)

We’ve got a lot of big challenges in medical science at the moment: cancer, AIDS, antibiotic resistance, neurodegenerative disorders, and a host of other things that we haven’t cured yet. Without animal testing, we’re not going to solve any of them very soon.

So rather than a question of practicality, the debate should solely rest upon fundamental morality: how many animals can be sacrificed to save one human life? The possible answers range from “none” to “an infinite number”, with “five rabbits and a marmoset” somewhere in between. I leave this as an exercise for the reader.

Those caveats in place, I’m very excited by Norman Baker’s announcement last week that he has a particular interest in developing non-animal alternatives, and I want to have a look at what those alternatives might be.

Mice (189,000), rats (99,200), other rodents (8,200), fish (42,500), birds (16,700), rabbits (10,100), and other animals (9,300, including 2,100 monkeys). (source)

Toxicology is a big area of animal research, because if you want to sell something that people will eat, rub on themselves, or just touch all day, you need to make sure that it’s not going to kill them. Non-animal toxicology tests are generally done in combination with animal tests, and act as early screening methods so that animal resources aren’t wasted on substances that are likely to be toxic.

The Ames test for carcinogenicity is one of my favourites. One of the ways that a substance can cause cancers is by directly causing mutations in the DNA of cells. The Ames test takes bacteria that have small mutations that make them unable to live without histidine, and mixes them with the compound under investigation, and then leaves them somewhere without any histidine for a while. If any of them survive, it’s likely that the substance helped them regain their ability to live without histidine by mutating their DNA.

Using human cells to test drugs on is a great idea as well, but what we really need is some idea of how the cells would act in the body. Usually, human cells live inside complex structures, as part of tissues and surrounded by an extracellular matrix. They are affected by blood vessels, nearby organs, and the other cells around them. One way to start to model this is by creating an organ-on-a-chip, where cells are grown on a tiny, microfabricated chip designed to mimic their natural environment, and connected by fluid to other groups of cells from the same organ. Researchers have been working on models of the lung, liver, kidneys and heart using this technology, but they haven’t yet been proven to be useful.

It can be difficult to get hold of human cells to use, and it’s even harder to keep them alive, so working out how to transform human stem cells into realistic versions of adult cells will be a huge step forwards in this field.

Finally, in silico approaches, in which we combine all the information we know about a bodily system into a mathematical model, and use it to predict results. My group in Oxford have done some interesting things predicting cardiac side-effects of drugs, and the Virtual Physiological Human project aims to collect together models of the entire body. We’re still a long way away from having computational models that are as refined as animal systems, but as we learn more about humans we can build better and better models.

It’s not just human models we need, either. For agricultural chemicals and ecology screens, we need to know the effects of new compounds on wildlife and farm animals, so we need excellent models of these systems as well.

When we can finally replace animal testing with equally effective alternatives, it will represent an enormous amount of effort, research and knowledge, and will amount to nothing less than the total, systematic understanding of the human body. Contrary to Mr. Baker’s pleas to industry to work on alternatives, the best place for this research is in universities and other non-profit organisations that are able to publish their results without losing a competitive advantage.

If you’re interested in reading more, the National Centre for the Replacement, Refinement and Reduction of animals in research (NC3RS) is an organisation in the UK that funds and co-ordinates research into animal alternatives, and Altex is a journal specifically dedicated to the 3 Rs.

Aside: cosmetics testing has been illegal in the UK for a number of years, but a lot of imported products (including those from P&G, Unilever and Estée Lauder) are tested on animals. It is essential to test products for safety; it isn’t essential to invent a new kind of shampoo twice a year. I think that human civilisation has probably created the best lipstick it’s ever going to, and despite the fact that anti-ageing creams have never been shown to work on a living creature, they still seem to sell fairly well anyway. To end animal screening for cosmetics that don’t fill a useful need like providing for people with allergies or eczema, we need to put pressure on the organisations that create them.