Humans

Most of us instinctively think that our sense of self is located in our head – but experiments show that our brains aren’t working alone in creating our sense of self

Humans 9 December 2020
By Alison George

Martin Parr/Magnum Photos

Where is your self?
FOR the Ancient Egyptians, it was the heart. For philosopher René Descartes, it was somewhere entirely separate from the body. According to the Buddhist concept of anatta, it isn’t anywhere, because the thing concerned doesn’t exist.
But what does modern science say about where your self – your “soul”, if you like – resides?
At first pass, that might not seem a particularly scientific question. Regardless, most of us have an intuitive answer. When, in as-yet unpublished work, Christina Starmans and her colleagues showed people from the US and India pictures of flies circling around a person, and asked which flies they thought were closest, the results were striking: regardless of cultural background, most people pointed to flies near a person’s eyes. “This suggests there is a universal sense of the self being located in the head, near the eyes,” says Starmans, a psychologist at the University of Toronto in Canada.
Subjectively at least, the eyes being windows to the soul checks out. “The sense of where in our bodies we are located is informed by our dominant experience of the world,” says Starmans. “Almost all of our input from the world comes in through our head.”
What our heads do with these inputs is certainly incredible, and key to our feeling that we are coherent beings. Our brains take a hotchpotch of electrical messages from our sense organs – eyes, ears, nose, skin – and combine them with memories to create a vivid, unified sense of conscious experience that is continuous in time.
How exactly this happens is still something of a mystery. But … More

We have a strong sense of continuous, coherent existence – yet from the cells that make our bodies to our defining character traits, we are in a constant state of change

Humans 9 December 2020
By Tiffany O’Callaghan
Each of us shows many differing faces over time
Getty Images

Are you always the same person?
MY MOM sometimes jokes that it is fortunate she didn’t meet my dad when he was in college, because she wouldn’t have liked him. She was (and is) a self-described goody two shoes. Dad not so much, but presumably even less so when keg parties were involved.
We know that we change over time. Our bodies grow, then age; we mature and our views shift; our memories sharpen and fade. Yet for most of us, our sense of self is seamless and continuous. You are the same old you, right?
Let’s start with the physical. Some of our cells, notably neurons in the brain, are with us from before birth, and can live more than 100 years. “Most of the nerve cells in the brain are actually as old as we are,” says molecular biologist Jonas Frisén at the Karolinska Institute in Sweden.
But most of our cells aren’t. Some, including certain kinds of white blood cell, live for only days. How quickly our skin cells are replenished changes as we age, but in general it takes about a month. The notion that the liver regenerates every 40 days or so is a myth: our liver cells live 200 to 300 days.
On the level of atoms and molecules, meanwhile, we are exchanging material with our environment with abandon. Think of your body like a grassy field, says Frisén. “It’s the same lawn from year to year, but each strand of grass is completely different.”
But what about less tangible … More

Foreign cells within our bodies help determine our mental states and even contribute to our immune defences – making it tricky to define where you end and the others begin

Humans 9 December 2020
By Graham Lawton

imageBROKER/Alamy

Where are your boundaries?
“Studies show we think of ourselves now and in the future as different people”
DELINEATING where a person begins and ends used to be quite simple. While philosophers might have tied themselves in knots trying to define the self, and biologists still struggle to locate its steering mechanism (see “Where is your self?”), what it encompassed, at least, was more clear-cut.
Their traditional definition comprises three elements, says Thomas Bosch at the University of Kiel, Germany: the mind, the genome and the immune system. Each of us is a self-contained organism defined by our mind and genes, with the immune system patrolling our borders and discriminating between self and non-self. Me, myself and I.
Then we looked more closely, and our relationship status went from “threesome” to “it’s complicated”.
For starters, we are chimeras: some parts of us are human, but genetically not “us”. Most, if not all, of us contain a few cells from our mother, our grandmothers and even elder siblings that infiltrated our bodies in the uterus.
Women who have carried children host such cells too. “Something like 65 per cent of women, even in their 70s, when autopsies were performed, had cells in their brains that were not theirs,” says David Linden at Johns Hopkins University in Maryland. Chimeric cells have been found to contribute to both good and bad health, for example promoting wound healing but also triggering autoimmune disease.
A handful of people even turn out to be true chimeras, created from a merger in the uterus of two non-identical, “fraternal” twins. We don’t know how common this … More

Understanding how individual we all are means grappling with genetics and neuroscience. Unique: The new science of human individuality by David Linden is a great place to start

Humans 9 December 2020
By Clare Wilson
Studying twins has shed light on the heritability of people’s personality
MStudioImages/Getty Images

Unique: The new science of human individuality
David Linden
Hachette
IN 1979, the US public was fascinated by news coverage of the “Jim twins”, a pair of identical twin brothers who were adopted at birth by different families, only to find each other at the age of 39.
The coincidence of their matching first names wasn’t their only similarity. They weren’t mirror duplicates of each other, in looks or temperament, but both worked in law enforcement and their hobby was carpentry. Both owned Chevrolets and took … More

According to the laws of physics, everything we do follows inevitably from what happened before – and yet we’re convinced we can change the world. Can we?

Humans 9 December 2020
By Richard Webb
If you don’t want to read this, put the magazine down now
Getty Images/Image Source

Are you predetermined?
WHAT are you doing right now? Reading these words. Why? Presumably because you chose to. Even if you didn’t – if you are encountering them years in the future lining a forgotten box of crockery in the attic, say – you can always choose to look away now. You possess the nebulous quality of human free will.
Nebulous because, despite debating it for millennia, philosophers have been unable to pin it down – and although we are pretty convinced we have it, at some level it must be an illusion, rather like our sense of self is (see “Are you always the same person?”).
Let’s start with the physics. Whenever you decide something, a certain pattern of neurons fires in your brain to turn your thought into action – moving towards the kitchen to make coffee, perhaps, or formulating an utterance you will come to regret. Ultimately, that is all down to pulses of electrons – fundamental particles that follow the cast-iron laws of physics, under which everything is determined by what happened immediately before.
That doesn’t leave much room for free will, apparently. “Physical laws, if they’re deterministic, tell me that everything that I do, everything that happens in the world, including everything that I do, including every decision I ever made, follows logically from the laws of nature [and] the initial conditions of the universe,” says philosopher of physics Jenann Ismael at Columbia University in New York. Since we control neither the laws of nature nor the initial conditions of the universe, we … More

It’s easy to be disheartened by the puniness of our existence – yet perhaps for the first time in human history, everything depends on decisions each one of us makes

Humans 9 December 2020
By Joshua Howgego

JohnnyGreig/Getty Images

Do you matter?
LET’S start with the big picture: if it is significance on this Earth you are looking for, then the numbers are increasingly against you.
Go back 2000 years and there were fewer than 200 million people on the planet. When the industrial revolution kicked in from the 18th century, however, new methods emerged of feeding vastly more people and combating the infectious diseases that had kept our numbers in check. Our numbers began to shoot up, reaching nearly 7.7 billion now. Today, you are, to a greater extent than in all history, just a face in a crowd.
That doesn’t mean you matter any less to your closest friends and family. And perhaps you or your offspring may be one of those few who change the world for better (or for worse). But that is statistically unlikely. Even in spheres where we like to think we are important, such as parenting, the evidence suggests individuals don’t matter that much. Geneticist Robert Plomin at King’s College London has pointed out, for instance, that identical twins brought up in different families generally end up with the same level of cognitive ability.
It isn’t just about you
But there is another, contrary, line of thinking, that collectively all of us can make a difference on a grand scale. In the broad sweep of human history, these are pivotal times. With the development of nuclear weapons in the mid-20th century, humanity reached a point where we can destroy ourselves. In this century, existential risks have only increased thanks to the threat of catastrophic climate change, … More

Covid-19 continues to split some people along party lines. We are now beginning to work out why, writes Graham Lawton

Humans | Comment 9 December 2020
By Graham Lawton

REUTERS/Mike Blake

LIKE the majority of people in my local area, I follow the rules on face coverings. It’s an inconvenience, but I consider putting on a mask a small sacrifice to protect my health and that of other people. Every day, I see many people – more than could possibly have a legitimate exemption – flagrantly flouting the rules and it really gets up my nose.
The refuseniks annoy me on multiple levels. They are selfishly putting me and other people at risk. They think they know better than experts. They often fall for conspiracy theories. And even if they are … More

By Colin Barras
Living in darkness, or even hibernating, could have left ancient humans with bone lesions
gorodenkoff/Getty Images

Some of the ancient humans living in Europe half a million years ago had a remarkable strategy for dealing with winter: they hibernated. At least, that is the claim being made by two researchers. Others dispute the evidence – but ongoing research suggests that it might be possible to induce a hibernation-like state in modern humans.
Sima de los Huesos – the “pit of bones” – lies in northern Spain and is one of the world’s most important sites for studying human evolution. Excavations at … More