Counterintuitive as it seems, vegetarians who don't eat meat because they consider it cruel could cause more harm to animals than actual meat production does. Professor Mike Archer argues that whatever we choose to eat, animals will still suffer.

Some vegans and vegetarians, not all, are kind of inclined to say, ‘Our diets are more ethical than your diets if you are an omnivore’.

Nobody is a pure carnivore, that I know, except maybe Eskimos with seals. The rest of us eat a bit of meat and a bit of plant material. After all, that is our heritage. We come out of a noble line of omnivores.

We did experiment at one point in human evolution with producing a herbivore, this was the 'Nutcracker Man', the ugliest sucker you have ever seen, a really hideous looking guy.

It didn't last very long. We are omnivores, we need those nutrients.

But no matter what you eat, animals die to enable it to happen. If you're going to eat a primarily vegetarian diet, if it's going to include grains, for example, we have monocultures that have been established at the expense of our naturally bio-diverse environments. Land has been swept clean.

Ten thousand years ago in the Near East when agriculture started, so too did the beginning of disasters for global biodiversity. We swept natural diversity aside on all continents to plant just a few species that we valued. In the mere act of producing lots of vegetarian food you are killing many animals.

These cute little guys, you can often see them twitching their nose and looking at each other but we didn't realise until somebody listened to them with an ultrasonic recorder that they are actually singing.

Take the example of what happens when you grow grains or pulses. In all the towns around Australia that are wheat producing towns or centres, on average about every five years they have a mouse plague. And these mice get killed in the millions and millions, mass slaughtered in horrible ways that cause their deaths to be really unpleasant. And that is going into producing grains. Some of those grains are fed to cattle, but they are also the core of the diets for a lot of people who don't want to eat any meat.

So when you think about mice, and we are talking now here about sentient lives, is the vegetarian or vegan's claim that their diets involve less death of sentient beings correct or not? When you actually do the sums you find, oh no, it's not clear at all that they are correct because all these mice, among other things, are being killed to make sure that we get those grains.

And mice, the research has recently shown, are much more sentient than we ever thought. Mice actually sing love songs to each other.

You can often see them twitching their noses and looking at each other but we didn't realise until somebody listened to them with an ultrasonic recorder that they are actually singing.

There are Carusos in there, wooing all the little mice. The experiments have shown that the girl mice flock to particular singers, and these singers change their songs, it's not just some kind of rote memory thing that is written into their genes.

This research has taught us we have to look at mice in a very different way. I mean, who else sings? Humans, whales. There are very few animals that actually sing, let alone love songs, and mice are among them.

The vegans and the animal liberationists and the animal rights people are desperate not to accept this message. So I have number-crunched in every conceivable way to try to diminish this issue. And you'd have to say, maybe they've chewed a couple of holes in the argument, but they can't possibly get away from the fact that our vegan or vegetarian diets involve the deaths of wonderful sentient animals.

Now, what can we do about it? Maybe there are other diets we can eat?

I think we can just stop being hypocritical.

That's what I'm really asking for; just accept the fact that in order for us to survive, other animals are going to die. It has been the way of life in ecosystems long before humans were on the planet. We can't change that, we can't stop death out there.

The Garden of Eden actually is a myth, sorry.

Professor Mike Archer is from the School of Biological, Earth and Environmental Sciences at the University of New South Wales. Listen to his conversation with Robyn Williams on The Science Show.