Ross G Menzies is, by his own admission, “a very old man” by the standards of the human species. A century and a half ago the average life expectancy was in the 30s, “so how can I whinge if I develop something today and [get] told that I’ll be dead by Christmas?” he jokes.

“If I can see that I am just one of the 107 billion that have lived, and that I will go to dust like all those before me, it is easier to face the difficult times that we are in.” He pauses. “Diminishing the self is one of the most important things that we can do.”

We live in a world that convinces us that we are the protagonists of our own stories, but for Menzies, there’s no better step a person can take in this disorienting moment in the world’s trajectory than to accept our cosmic insignificance. To acknowledge our nature as “a collection of atomic particles”.

The acclaimed psychologist and his daughter, the fellow psychologist and academic Rachel E Menzies, have just published Being: Why it’s harder to be human than a hamster or a herring. Ross tells me it is harder to be human than it is to be “any other animal”. But making peace with our smallness, he says, can have outsize power.

Ross, who is travelling in San Francisco when we speak, is talking to me over WhatsApp, his image fittingly tiny. Rachel, an articulate and thoughtful presence, known for her pioneering work on death anxiety, is sitting at a table beside me in a Sydney boardroom at the Australian duo’s publisher, Allen & Unwin. It is the week before the release of their anticipated follow-up to their bestselling 2021 book Mortals: How the fear of death shaped human society. The new book weaves voices from the worlds of psychology and philosophy – Aaron Beck, Heidegger – with examples from ancient and contemporary culture and observations from their combined five decades of research and clinical practice.

Among the most powerful ways that humans can deal with the weight of their suffering, the Menzies say, is to accept that we may not truly possess free will.

It is part of an emerging wave of thinking – championed by philosophers such as Sam Harris and neuroscientists such as Robert Sapolsky – that grapples seriously with the question of whether we truly chart the course of our lives, or whether what we presume is our agency at work is actually more likely the result of cause and effect. This chimes with what the Stoics believed in ancient Greece and Rome: that we are part of an interconnected universe, whose laws are already written for us.

“I think Stoicism often gets a bad rap,” Rachel says. The popular resurgence of Stoic philosophy is linked to its idea that our ability to make choices free from external forces is limited. But, importantly, this doesn’t mean surrendering our desire to live well, or our duties to each other.

“The Stoic philosophers were working with the emperor,” she says. “They were politicians. They were senators. They weren’t stepping back from society. They recognised what was within their control, what they wanted to push for and change, and what wasn’t.”

Being traverses a lot of terrain, but it closes with chapters titled The illusion of freedom, and The return to nothingness. The Menzies see the surrender of free will not as a way to reject moral responsibility, but rather to reduce the pain we carry. “Once you accept the fact that you are made up of atomic particles that must act in a determined way, that there are distributed causes that are playing out across time, then it is far easier to be gentler to the self and to others,” Ross says.

This counters the belief, central to modern life over the last few centuries, that we can fashion our destinies according to our own choices. This individualist idea, rooted in Enlightenment thinking, is heightened during this capitalist moment, accelerated by the forces of self-surveillance and artificial intelligence which mirror our selves back to us while holding us personally responsible for systemic failures.

Rachel says this doesn’t mean taking a fatalistic approach to the future. “We can still be disappointed by how things turn out, or want consequences if someone did something immoral or illegal,” she says. “It can be a difficult idea to sit with because we want to blame other people or want to blame ourselves, but the reality that might not be whole picture softens the suffering.”

Our neoliberal world is obsessed with the self, the cults of individual choice and personal agency. These conditions, the Menzies argue in Being, make us anxious and unhappy. Instead, the book proposes the value of acknowledging our kinship with humans across time and meditating on the improbability of our place in the cosmos.

“The three of us in this conversation have won the genetic lottery against all the odds,” Ross says with a smile. “It is an extraordinary win to have existence and be sensate.”

The ‘flawed’ inner voice

There are facets of being human, the Menzies say, that separate us from other mammals. The book opens by exploring the inner voice, the interior monologue that as the Menzies put it “chatters away in our own tonality”, which as far as we know is a distinctive to our species.

“The nature of having this voice in our skull means that it is impossible to ignore it, but we take it to be a helpful voice, we take it as fact, when it is often telling us things that that are harmful and destructive,” Rachel says.

“Early behavioural therapy was trying to show people that the inner voice was flawed,” Ross adds. “All the major thinkers of the last century have told us to change our relationship with the inner voice. The jury is out on the best way to achieve it.”

The inner voice, of course, is also shaped by factors beyond our control, they argue. Messages we receive from the culture. The conditioning we receive from our families, which according to Being is among the most important catalyst for our fate.

“Something as simple as the order in which we are born, or growing up with parents who are warm and supportive versus critical and unpredictable, continues to influence mental health and romantic relationship decades into the future,” Rachel muses. In Being, the pair point out that in bird species – such as the black eagle – chicks are known to peck their new siblings to death within days to maintain their resources, echoing the total dependency on caregivers in human survival.

Ross, who listens carefully to Rachel, often turning over different facets of his daughter’s points, tells me that humans are social primates, who suffer the damage of poor attachment in early life. “It predicts premature death from all causes,” he says.

“For most of human history, we lived in a village, we worked together,” Rachel smiles. “Now we work from home, or don’t have interactions with other people and that creates problems. I think it is much easier to feel lonely and not part of the community – I think there are less inbuilt social structures for people to connect now.”

The problems of existential isolation, I say, feel more pointed in a world facing ecological catastrophe, where technology is confining us to our private bubbles of experience. But for the Menzies, who in Being make a case for social prescribing (meaningful group activities such as joining a community garden, or group choir rather than drugs to treat mental and physical ailments), this reflects the paradox of being human.

“One of [our] central needs is to connect with other people. We need love, we need a feeling of belonging,” Rachel says, her tone emphatic. “At the same time, we will never be able to fundamentally connect with another person because they live behind a different set of eyes.”

Existence is difficult, Ross says. But in writing Being, the Menzies hoped to reach people, to remind them they are part of a universe, joined to other humans like them.

“That tension is really interesting – the need for love and connection while knowing that we will never cross that bridge is quite a painful thing,” says Rachel. “But I think there is something optimistic about the fact that we keep trying.”

• Being: Why it’s harder to be a human than a hamster or a herring by Rachel E Menzies and Ross G Menzies is out now through Allen & Unwin