Our distant ancestors left us with moral baggage for a different world, but now morality needs to be modernised to fit our times, says philosopher Tim Dean.
In his debut book How We Became Human: And Why We Need To Change, Dean examines how we evolved and why some of our evolved inclinations are out of step with the modern world.
He has written this book for W.E.I.R.D (Western, Educated, Industralised, Rich, Democratic) people, he says, to encourage reflection and change.
Over the years men gained more and more power and used it to entrench their own sexual morality, Dean says.
"The thing is we have inherited a lot of that cultural baggage that is still with us today and is still influencing the way we live, even though it is no longer fit for the world, [and] it was never really fit for the world.
"I use Victorian England [in the book], not to say this is the only place where this kind of sexual oppressive morality existed, it's just the exemplar of a sexual morality that emerged during agricultural times.
"This is when our species went from living in small scale societies, which were very egalitarian and sexually quite open and diverse and tolerant, to being settled, concentrating resources and wealth."
Our inheritance of this morality can also partly explain some of the opposition to things like abortion and contraception, he says.
"This is a moral thing where the facts alone, in terms of embryonic development, are not going to be able to define exactly when a human being is formed. This is a much more complicated question and this is what makes it difficult to negotiate between these two different moral views.
"It becomes to a point where people then project what is useful for their particular moral perspective."
He believes it's well overdue for us to push back against this force of morality.
"I'm loathe to tell women what they should be doing with their bodies because that's my moral stance, which favours the ability for people to take charge of their own body."
Anti-vaxxers are another group that seek the right to autonomy over their body, but Dean says the difference here is that there is potential harm to others involved.
"I suspect to some degree, one reason why some people are resisting the vaccination is because we in some cases have lost a sense of community, we've lost a sense of belonging, and interestingly this is something our distant ancestors in hunter-gatherer times had in spades."
One of the potent moral emotions humans used over time to live harmoniously is outrage, Dean says, because we feel it when we see injustice being committed to anyone.
"In small scale societies, this had a profound effect on the way we lived ... that would gather together a coalition of people who would intervene, and they would try to correct that wrong."
In modern times, that's being replicated in social media but what's missing is our ability to correct wrongdoings, Dean says.
"It's making us angry, it's making us miserable, it's making us tired, and it's not actually - in most cases - making the world a better place.
"We are now very mindful of what it means to be in a pandemic, we're very mindful of what it means to spread something to others that might harm them, outrage is no different.
"Instead don't follow the people who make you outraged ... and if you do get outraged, think twice about spreading it."
On the other hand, there have been cases where spread of experiences via social media have helped bring change, like the MeToo and Black Lives Matter movements, he says.
Too much moral conviction is the problem we face today, where our view of right and wrong is being projected onto everybody else, he says.
"What happens is if we become too fixated, too certain and too immovable in our morality, we get a couple of problems, one is we fight with others ... [and] we're willing to make great sacrifices to get our moral way.
"I don't think morality is built into the world, I think it's a very human thing. We have these evolved inclinations to empathy and outrage, they help to some degree... but really the rules that we live by are things that humans create, we negotiate them.
"This is a negotiation that is stifled when there is too much moral certainty. We need to have a little humility to be able to engage."
Tim Dean has a doctorate in philosophy from the University of New South Wales on the evolution of morality, specialising in ethics, critical thinking, the philosophy of science and philosophy education.