What makes human beings special

The list might be smaller than it once was, but there are some traits of ours that no other creature on Earth can match. No animal can get close to the devastation humans can cause Credit: Thinkstock. Ever since we learned to write, we have documented how special we are.

The philosopher Aristotle marked out our differences over 2, years ago. We are " rational animals " pursuing knowledge for its own sake. We live by art and reasoning, he wrote. Much of what he said stills stands. Yes, we see the roots of many behaviours once considered uniquely human in our closest relatives, chimpanzees and bonobos. But we are the only ones who peer into their world and write books about it.

We have similarities with everything else in nature; it would be astonishing if we didn't. To understand these differences, a good place to start is to look at how we got here.

Why are we the only human species still alive today whereas many of our early-human ancestors went extinct? Neanderthals left didn't fare as well as we did Credit: SPL. Humans and chimpanzees diverged from our common ancestor more than six million years ago. Fossil evidence points to the ways which we have gradually changed.

We left the trees, started walking and began to live in larger groups. And then our brains got bigger. Physically we are another primate, but our bigger brains are unusual. We don't know exactly what led to our brains becoming the size they are today, but we seem to owe our complex reasoning abilities to it. It is likely that we have our big brain to thank that we exist at all. When we — Homo sapiens — first appeared about , years ago we weren't alone.

We shared the planet at least four other upright cousins; Neanderthals, Denisovans, the "hobbit" Homo floresiensis and a mysterious fourth group. The human brain is advantageously big Credit: Thinkstock. Evidence in the form of stone tools suggests that for about , years our technology was very similar to the Neanderthals. But 80, years ago something changed. Once H. We started to produce superior cultural and technological artefacts. Our stone tools became more intricate. One study proposes that our technological innovation was key for our migration out of Africa.

We started to assign symbolic values to objects such as geometrical designs on plaques and cave art. By contrast, there is little evidence that any other hominins made any kind of art. One example, which was possibly made by Neanderthals, was hailed as proof they had similar levels of abstract thought.

However, it is a simple etching and some question whether Neanderthals made it at all. The symbols made by H. We had also been around for , years before symbolic objects appeared so what happened? We had the capacity for art early in our history Credit: SPL. Somehow, our language-learning abilities were gradually "switched on", Tattersall argues. In the same way that early birds developed feathers before they could fly, we had the mental tools for complex language before we developed it.

We started with language-like symbols as a way to represent the world around us, he says. For example, before you say a word, your brain first has to have a symbolic representation of what it means. These mental symbols eventually led to language in all its complexity and the ability to process information is the main reason we are the only hominin still alive, Tattersall argues.

It's not clear exactly when speech evolved, or how. But it seems likely that it was partly driven by another uniquely human trait: our superior social skills. We also possess a descended hyoid bone — this horseshoe-shaped bone below the tongue, unique in that it is not attached to any other bones in the body, allows us to articulate words when speaking.

Humans are unique among the primates in how walking fully upright is our chief mode of locomotion. This frees our hands up for using tools. Unfortunately, the changes made in our pelvis for moving on two legs, in combination with babies with large brains, makes human childbirth unusually dangerous compared with the rest of the animal kingdom. A century ago, childbirth was a leading cause of death for women. The lumbar curve in the lower back, which helps us maintain our balance as we stand and walk, also leaves us vulnerable to lower back pain and strain.

We look naked compared to our hairier ape cousins. Surprisingly, however, a square inch of human skin on average possesses as much hair-producing follicles as other primates, or more — humans often just have thinner, shorter, lighter hairs. Fun fact about hair: Even though we don't seem to have much, it apparently helps us detect parasites , according to one study. Humans may be called "naked apes," but most of us wear clothing, a fact that makes us unique in the animal kingdom, save for the clothing we make for other animals.

The development of clothing has even influenced the evolution of other species — the body louse, unlike all other kinds, clings to clothing, not hair. Without a doubt, the human trait that sets us apart the most from the animal kingdom is our extraordinary brain.

Humans don't have the largest brains in the world — those belong to sperm whales. We don't even have the largest brains relative to body size — many birds have brains that make up more than 8 percent of their body weight, compared to only 2. We use animals in science every day to try to understand complex biochemical pathways in order that we might develop drugs or understand disease. Mice, rats, monkeys, even cats, newts and armadillos, provide invaluable insights into our own biochemistry, but even so, all researchers acknowledge the limitations of those molecular analogies; we shared ancestors with those beasts millions of years ago, and our evolutionary trajectories have nudged that biochemistry to suit each species as it is today.

When it comes to behaviour, though, the parallels frequently become distant, or examples of convergent evolution. The fact that a chimpanzee uses a stick to winkle out a fat grub from the bark of a tree is a trick independent of the same ability in Caledonian crows, whose skills are frequently the source of increasing wonder as we study them more. What this inevitably means is that using tools is a trick that has been acquired many times in evolution, and it is virtually impossible to assume a single evolutionary antecedent from which this behaviour sprang.

Chimps sharpen sticks with their teeth with which to kebab sleeping bush babies. There is no evidence that these similar behaviours show continuity through time. Arguments around these issues are generally the preserve of scientists.

But there is a set of behaviours that are also inspected forensically and with evolution in mind whose reach extends far beyond the academy.

Most animals are sexual beings and the primary function of sex is to reproduce. The statistician David Spiegelhalter estimates that up to ,, acts of human heterosexual intercourse take place per year in Britain alone — roughly , per hour.

Around , babies are born in Britain each year, and if we include miscarriages and abortions, the number of conceptions rises to about , per year. What that means is that of those ,, British encounters, 0. Out of every 1, sexual acts that could result in a baby, only one actually does.

In statistics, this is classed as not very significant. If we include homosexual behaviour, and sexual behaviour that cannot result in a pregnancy, including solitary acts, then the volume of sex that we enjoy magnificently dwarfs its primary purpose. Is Homo sapiens the only species that has decoupled sex from reproduction? Enjoying sex might seem like a uniquely human experience, yet while we are reluctant to consider pleasure in other animals, we are certainly not the only animals that engage in non-reproductive sex.

Zoo behaviour is often weird, as animals in captivity are far from their natural environment, but there are two male bears in Zagreb zoo who enjoy a daily act of fellatio, while simultaneously humming.

Males of some 80 species, and females of around 50 species of primates are frequent masturbators. Some behaviours reflect deviant or criminal sexual behaviours, such as sea otters who drown females and then keep their bodies to copulate with.

The award for sheer ingenuity goes to the dolphins: there is one reported case of a male masturbating by wrapping an electric eel around his penis. Some — not all — of these seemingly familiar sexual practices can be explained readily. Male Cape ground squirrels are promiscuous, and masturbate after copulation, we think, for hygiene reasons, protecting themselves from sexually transmitted diseases by flushing their tubes.

Other behaviour is still mysterious to us: giraffes spend most of their time sexually segregated, and the vast majority of sexual relations appear to be male-to-male penetration. As with the myriad examples of sexual behaviour between members of the same sex, it demonstrates that homosexuality — once, and in many places to this day, decried as a crime against nature — is widespread.

Because sex and gender politics are so prominent in our lives, some look to evolution for answers to hard questions about the dynamics between men and women, and the social structures that cause us so much ire. Evolutionary psychologists strain to explain our behaviour today by speculating that it relates to an adaptation to Pleistocene life. Briefly, issues with that idea are pretty straightforward: most fruit is not red; most skin tones are not white; and crucially, the test for evolutionary success is increased reproductive success.

No, we do not. Peterson is also well known for using the existence of patriarchal dominance hierarchies in a non-specific lobster species as supporting evidence for the natural existence of male hierarchies in humans.