There is a picture on page 116 of this book that hurts to look at.

It is of an animal that looks a bit like a dog and a bit like a cat; its fur is a bit like a zebra's and a bit like a fox's. It is called a thylacine and the last known survivor of the species died in 1936. The picture, taken in London Zoo in 1913, hurts because we did this: we killed it.

There are many other species like the thylacine in Richard Girling's book: animals driven beyond the edge, as well as animals being shuffled towards it. However, the book is not a howl of anger at this situation - justified though that would be. It is an exploration of what extinct means and a reminder that such a label is almost as arrogant as the behaviour that wiped out species like the thylacine in the first place.

Girling's point is we simply do not properly know what is out there and yet think we can say with authority what does or does not exist. Not only does his book include a suggestion that a third of all supposedly extinct animals are still alive, it also reminds us that many species are not known to man, and others barely known, such as the Somali golden mole of the title. The only evidence of the mole's existence is a jawbone found in Somalia but the mole could be out there right now, getting on with its life. It does not need to be labelled by us to exist.

By pointing out there is a mass of animal life we know nothing about, Girling is not denying there is an issue with protecting the animals we do know about (quite the opposite: he spells out the problem of extinction in disturbing detail). Rather, he is reminding us that what he calls our mountain range of stupidity about animals should make us cautious about how we behave towards them.

Girling also reminds us of the hypocrisy of our modern attitudes and our tendency to look back at the early days of zoos and hunting and assume we are better. Not so, he says.

In the first few pages, he relates the story of the 19th century Scottish hunter Roualeyn Gordon-Cumming who was happy to shoot big game but could also show compassion towards a dog in pain. Girling says we should not judge him too harshly. "It ill behoves the 21st century to accuse the 19th of double standards when we have enough of our own," he says. "Our attitudes to animals are determined by the labels we attach to them - pet, food, pest, vermin. Shuffle them around and the result is almost viscerally disturbing. Pony-veal? Cat-traps? Dog-hunts?"

The aim of Girling's book is to explore this and other issues while searching for the jawbone of the Somali golden mole. The problem is the so-called hunt amounts to no more than contacting the man who has it and going to see it. Girling postpones this moment until the last chapter but even then is forced to pad the chapter out with descriptions of what he was wearing and other unnecessary facts.

Does this undermine the book? A little because it is irritating, but what is most important is what Girling has to say about the extent of our ignorance. We know what happened to the thylacine but on page 263 there is another picture of an animal that is just as fascinating. It is a species of rabbit-sized shrew that was unknown until it was photographed in Kenya in 2010. Now loggers are moving into its territory that means a species that has just been found could soon be lost. Which, in turn, leads to what Girling calls the ultimate test for human beings: to prevent the celebration of discovery from turning immediately into the mourning of loss.