A Brief History of Everyone Who Ever Lived: The Human Story Retold Through Our Genes

by Adam Rutherford

This is a seam that will run throughout this book, confronting and dispelling the culturally ubiquitous idea that genes are fate, and a certain type of any one gene will determine exactly what an individual is like. That this is a fallacy is universally known among geneticists, yet it is still an idea that carries a lot of cultural significance, fueled frequently by the media and an ultra-simplistic understanding of the absurd complexities of human biology.

Knowing the gene sequence in an individual provides some limited information, unless they have one of a relatively small set of genes that have a very significant effect.

By comparing sections of Neanderthal DNA with sections of DNA in modern humans that we think have come from Neanderthals, we can build up a very finely tuned model of the success, from an evolutionary point of view, of these hybridizations. When Graham Coop and his colleagues did this, they found that our genomes are slowly purging themselves of Neanderthal DNA, which suggests that these matings were not to our advantage, but not massively disadvantageous. Our DNA around Neanderthal chunks is undergoing weak negative selection,

The observation that there is less Neanderthal DNA on our Xs implies that the first encounters we had with them that resulted in procreation were male Neanderthals with female Homo sapiens.

We can’t tell why we have been slowly rejecting their DNA for thousands of generations. One of the important lessons here is that it demonstrates the speed of evolution, or rather, its breathtakingly slow burn. Any seriously deleterious effects would have been wiped out immediately, and maybe lost to time.

Around a million years ago, somewhere in Africa, a group of humans lived who were to be separated into us, the Neanderthals, and the Denisovans.

The comparison in the new genomes showed that Denisovans and Neanderthals were more closely related to each other than either was to any living human. But the real kicker came with the revelation that Denisovan DNA was alive and well in contemporary Melanesians—the indigenous people of Fiji, Papua New Guinea, and a scattering of islands off the northeast coast of Australia. Just as the Neanderthals left their permanent mark in me and you if you are of Eurasian descent, these other people, known only from this single bone, imprinted their genetic mark through the ages in the ancestors of these island people, up to 5 percent of their genomes.

Because of their proximity to the Japanese, 881 Aleuts of the Alaskan island chain were interned during the Second World War following the attack on Pearl Harbor, their houses burned by US troops to prevent the Japanese from using them. The Aleuts were housed in conditions far worse than the 700 Nazis who were captured in North Africa and imprisoned a few hundred miles away in Alaska.

The stigma of a genetic predisposition to alcoholism remains among Native Americans to this day, despite the fact that it is a claim not rooted in fact.

One fifth of people alive a millennium ago in Europe are the ancestors of no one alive today. Their lines of descent petered out at some point, when they or one of their progeny did not leave any of their own. Conversely, the remaining 80 percent are the ancestor of everyone living today. All lines of ancestry coalesce on every individual in the tenth century.

Our findings suggest a remarkable proposition: no matter the languages we speak or the color of our skin, we share ancestors who planted rice on the banks of the Yangtze, who first domesticated horses on the steppes of the Ukraine, who hunted giant sloths in the forests of North and South America, and who laboured to build the Great Pyramid of Khufu.

You are of royal descent, because everyone is. You are of Viking descent, because everyone is. You are of Saracen, Roman, Goth, Hun, Jewish descent, because, well, you get the idea.

If you’re a human being on Earth, you almost certainly have Nefertiti, Confucius, or anyone we can actually name from ancient history in your tree, if they left children. The further back we go, the more the certainty of ancestry increases, though the knowledge of our ancestors decreases. It is simultaneously wonderful, trivial, meaningless, and fun.

When we look to the past and to our presumed genetic ancestry to understand and explain our own behaviors today, it is not much better than astrology. The genes of your forebears have very little influence over you. Unless you carry a particular disease that has passed down the family tree, the unending shuffling of genes, the dilution through generations, and the highly variably and immensely complex influence that genes have over your actual behavior mean that your ancestors have little sway over you at all.

It can’t be stated enough that there is no test for Viking DNA, but I can assure you that if you are white, you have Viking ancestry.

The only way we could ever definitely say where your genetic origins are a thousand years ago would be to dig up the bodies of everyone who lived a thousand years ago, and then compare them. And the answer would be that your genetic origins are, in fact, in everyone.

If you want to spend your cash on someone in a white coat telling you that you’re from a tribe of wandering Germanic topless warriors, or descended from Vikings, Saracens, Saxons, or Drogo of Metz, or even the Great Emperor Charlemagne, help yourself. I, or hundreds of geneticists around the world, will shrug and do it for free: You are. And you don’t even need to spit in a tube—your majesty.

We know that the emergence of the pale skin we associate with Europe, and particularly northern Europe, only emerged in the last few thousand years, just as the genes for processing milk did.

There is no single gene that underpins the concept of race, just like there are so few genes for any one complex human characteristic, and there are just a few that convey the broad physical differences that render populations very visibly different from each other.

With these cluster analyses, it is true that the most similarities examined are shared within a group, but plenty overlap with other clusters. The graphical representations of these types of data show blending at the edges. The sharpest delineations coincide with water: Europe, sub-Saharan Africa, and East Asia. But with the addition of more groups, with fewer oceanic gulfs, human variation is pretty continuous. The concept of a discrete or pure race vanishes in the haze.

certain genetic groupings do roughly correspond to geography. But not exclusively, and not essentially. The analogy does though satisfy the question of how many races there are: It is unanswerable. It is a meaningless question.

there’s no evidence that Native Americans have any versions of genes that metabolize alcohol any differently from white people in America, nor is there a simple single genetic factor that might render someone an alcoholic. There is plenty of evidence for brutal social and cultural experiences for many Native Americans, and generations of oppression, resulting in underemployment, poverty, and low socioeconomic status, all of which are risk factors for alcoholism. Yet, the notion that the high rates of alcoholism in Native Americans—almost twice as high as in white European immigrant Americans—are somehow genetic remains an oft-repeated idea.

There’s no such thing as a Jewish disease, because Jews are not a genetically distinct group of people.

Sport is sometimes cited as the great leveler, a forum in which only talent and sheer grit will win the day. The idea that black people are better at sport because of genetics, and possibly because of breeding during the wicked centuries of slavery, is built upon tissue foundations, and its cultural ubiquity yet another example of the chasm between what we think, and what science says is true.

Genetics has revealed that human variation and its distribution across the planet is more complex and demands more sophisticated squinting than any attempts to align it with crude and ill-defined terms like race, or even black, or white. It is for this reason that I am comfortable stating that from the point of view of a geneticist, race does not exist. It has no useful scientific value.

Genetics has shown that people are different, and these differences cluster according to geography and culture, but never in a way that aligns with the traditional concepts of human races.

the penetrance of video gaming for teenage boys in the United States was around 84 percent in 2015—meaning that the vast majority of teenage boys play video games. Even with the soul-crushing frequency of spree shootings reported, the statistical relationship between playing violent video games and enacting murder is irrelevant. Because games are so widespread, statistically, the idea of a causal link between violent video games and murderous violence is absurd.

Ignorance more frequently begets confidence than does knowledge . . . says Darwin in The Descent of Man, his study of the evolution of humans from our hairier ancestors. It’s no secret that arguing with creationists is a waste of time, for they see things differently from most. They know that what they think is true, and in science we must assume we are wrong.

The genetics of the dead is a science moving at exhilarating speed, and reports of bones replete with new sources of DNA are being published on a weekly basis. But in April 2017, Viviane Slon, Svante Pääbo, and a Spanish team managed to do something almost magical. They had been to seven caves known to have once been homes to Neanderthals and Denisovans. They took sediment samples and succeeded in extracting wisps of mitochondrial DNA directly from the dirt. There in the cave floors, they found ghostly traces of the genes of woolly rhinos, cave bears, mammoths, and humans. We can now find the DNA of ancient people in places where bones no longer linger, and the door to past lives creaks open even further.