Should we try to think of ourselves not as individuals but as parts of the physical and cultural ecosystem? Tom Oliver, an ecologist specialising in land use, the climate crisis and biodiversity, believes we need a major shift in that direction. His view is that science now demands this change, and that only by making it will we become capable of responding to global warming and a host of other problems. The idea of the self as a relatively closed system is a delusion that has often conferred advantage, but is now a dangerous trap. Moving through difficult science with valuable clarity, Oliver tells us why.

He starts with the science of the body. Complex forces make it, sustain it and break it down. Like the body itself, these forces are not closed systems with hard outer boundaries. The atoms that compose us derive from the fusion of hydrogen and helium in the big bang, and many come from far regions of the universe. The molecules that form our bodies have travelled the atmosphere and perhaps been in other animal body parts. Viruses and bacteria bring in new genes. Our cells live for seven to 10 years on average, some only for days, weeks or months. Oxygen, food and water enter our bodies, while heat and waste leave us for other parts of the system.

Bacteria and fungi inhabit our bodies, their 38tn cells outnumbering ours. A human mouth contains over a thousand species. Genes pass between them. New species invade. Some leave or die, perhaps because of something we eat or stop eating. Some stay for life. Many are part of the functioning of our bodies. Even inside our cells there are mitochondria, energy-generating organs inherited from bacteria that fused with our single-celled ancestors two billion years ago. Correction: they were some of our ancestors.

Gut bacteria break down food for us. Intestinal bacteria have a protective effect against illnesses including bowel cancer, while others release molecules that increase our susceptibility. Even feelings and actions, which we might think define our identity, are not necessarily simply our own. Bacteria make a difference to moods and depression. Alarmingly, there are parasites that assist their own life cycles by modifying their hosts’ behaviour, for example toxoplasma, which makes rats behave recklessly and expose themselves to predation. People who carry this organism are more likely to be involved in traffic accidents.

As capitalism has become global, the consumerist idea of self has spread. But Oliver hopes we may be approaching a tipping point

Neuroscience brings more evidence. When we experience thoughts and memories, what happens physically is that electrochemical impulses travel between neuron brain cells, forming paths. The collection of paths at any one moment comprises that person’s “connectome”, which is the best match for our concept of self that materialist science can produce. Like other parts of the body, it is always being moulded by the world. Oliver quotes Susan Greenfield’s view that identity is an activity, not a state. New paths constantly form in huge numbers. Some paths fall into disuse, or the neurons reabsorb them. Oliver uses the image of a well-trodden road compared to an overgrown track. Selfhood holds its shape only through use. He compares the neurites, the millions of miles of connecting filaments in a brain, to the fibre-optic cables, mobile phone masts and satellites that enclose the globe in a web of technological communication. Both are parts of the process that forms our identities, as are the land and the climate.

As western capitalism has become global, the consumerist idea of self has spread further. Advertising presents consumers with visions of their selves enhanced by the possession of each new commodity or ability. The structures that reinforce this kind of self are formidable; nevertheless, Oliver hopes that we may be approaching a tipping point. The science that finds the outside world at work in all our components of selfhood is pulling us that way, as is the immensity of the ecological crisis.

His tone changes. The book’s title recalls Richard Dawkins, and, early on, Oliver occasionally shows a Dawkins-like exasperation at the world’s refusal to fall into line with objective science. For each of us, I presume, our consciousness feels like a centre, a fixed point from which we see things, however aware we are of the problems with this view. To Oliver, initially, this stubbornness resembles that of the flat-earthers who refused to accept the Copernican revolution. Yet he comes to see that the individualistic concept of self is a more ambiguous case. Qualifying adjectives start to appear more frequently. The independent, atomised, unchanging, coherent, autonomous self is the problem. We do not have to reject all forms of individuality.

That individualistic idea of self has had great advantages, both evolutionary and moral; care for the self is a primal motive for ingenuity in finding food, shelter and reproductive success. But Oliver calls it a white lie, an adaptive delusion. In small precarious communities, the need for sharing and mutual protection will have been a strong counterbalancing force, making excessive selfishness costly. Perhaps it is only in the context of ecological crisis and global consumerist capitalism that the adaptive delusion has become maladaptive, and the moral balance is tipping. And it is not reassuring to recall those societies in which masses of people have been willing to die for a collective identity such as nation, religion or a political cause. Essential to Oliver’s argument here is the moral difference between a collective identity that defines itself against others, and the ecosystem, which has no outsiders. Accepting the science is only the beginning. Moral weighing and reweighing must never stop.

At the end, I was curious. What will we fear and desire in this future? How differently will we fall in love? Will we be more reconciled to mortality? What will our favourite stories be like? These will be fascinating questions if the shift begins in earnest. This timely, challenging book tells us why it just might.

• The Self Delusion is published by Weidenfeld & Nicolson (£20). To order a copy go to guardianbookshop.com. Free UK p&p over £15.