Most media interest in evolution revolves around whether the eye developed through incremental, evolutionary change or whether the latest bone unearthed in Olduvai Gorge belongs to the "missing link". But there are questions about less tangible things as well. One of the stickiest is the existence of free will. Can you make choices, or are all of your actions determined? If you really can choose freely, that suggests that human beings have a immaterial element, a soul. But if you think that humankind is completely material, ultimately all of our choices are determined for him (or her).

Evolutionary psychologists have been very busy in recent years gathering evidence for the non-existence of free will. Last year, for instance, researchers at the Max Planck Institute, in Germany, used brain scanners to show that brains decide 7 seconds before people are aware of making a choice." Still to be investigated are the milliseconds before the choice is made. "We can't rule out that there's a free will that kicks in at this late point," said the lead author of the article in Nature Neuroscience. "But I don't think it's plausible."

Such remarks are par for the course in the major science journals. Much of the latest research "demonstrates" that human behaviour is never self-generated and that human freedom is an illusion. This is, of course, is a matter of no little consequence for human dignity.

So there’s good news and bad news about free will in a recent issue of Nature, the world’s leading science journal. The good news is that last week a Nature author was arguing that free will exists. Martin Heisenberg, of the University of Würzburg, in Germany, writes: "self-initiated action is not in conflict with physics and can be demonstrated in animals. So humans can be considered free in their behaviour, in as much as their behaviour is self-initiated and adaptive." He believes that one key to solving the ancient conundrum of free will is to be found in behavioural biology.

Take the common bacterium Escherichia coli. The way it moves by rotating its flagellum (or "tail") is random and inherently unpredictable. Professor Heisenberg says that this reflects the uncertainty of quantum physics. "What this tells us is that behavioural output can be independent of sensory input."

And that’s the bad news. Dr Heisenberg has rather bizarrely proved that humankind has free will by showing that a bacterium does, too. An expert on fruit flies, he sees that "there is plenty of evidence that an animal's behaviour cannot be reduced to responses. For example, my lab has demonstrated that fruit flies, in situations they have never encountered, can modify their expectations about the consequences of their actions. They can solve problems that no individual fly in the evolutionary history of the species has solved before." Sounds a bit like Star Trek, doesn’t it? To boldly go where no fruit fly has gone before.

How can Nature possibly promote the notion that free will exists on a sliding scale, from bacteria to humans? The basic problem is that its editors are 110% committed to promoting a thoroughly materialistic view of human evolution. This reductivism is rather silly – and not for "religious" reasons. Human beings obviously have a capacity for abstract knowledge which transcends what we can touch, see and measure. How else can we account for beauty, or for mathematics, or for our interest in a future which does not yet exist? It is simply logical to accept the evidence of everyday experience that humans are exceptional animals which really do have free will. It is simply illogical to assert categorically that there is no such thing and that all evidence to the contrary can be breezily explained away with quantum physics.

Professor Heisenberg’s "freedom" isn’t the same one that has enraptured lovers of freedom throughout the ages. It’s basically a sophisticated kind of determinism. But his article is instructive. It suggests two things: (1) that without the existence of an immaterial element, it is impossible for us to have freedom and (2) that most scientists know very little about philosophy. The philosopher Jean-Paul Sartre wrote famously that "man is condemned to be free". It’s unlikely that he thought that Escherichia coli.was rattling the same chains.