Humans

By Krista Charles

A very small part of our genome might be unique to modern humansCueImages/Alamy
Modern humans have been around for about 350,000 years. In that time, we have continued to evolve and our DNA has changed – but, only a small per centage of our genome may be unique to us.
Nathan Schaefer at the University of California, San Francisco, and his colleagues created a tool called the Speedy Ancestral Recombination Graph Estimator (SARGE), which allowed them to estimate the ancestry of individuals.
More specifically, it helped identify which bits of the modern human genome aren’t shared with other hominins – meaning they weren’t present in the ancient ancestors we shared with Neanderthals and Denisovans, and also haven’t been introduced to the human gene pool through interbreeding with these ancient humans.Advertisement
“Instead of building a tree across the genome that shows how a bunch of genomes are related on average genome-wide, we wanted to know what the ancestry of individuals looks like at specific sites in the genome,” says Schaefer. “We basically wanted to be able to show how everyone is related at every single variable position in the genome.”
The team analysed one Denisovan, two Neanderthal, and 279 modern human genomes to distinguish what parts of the genome separate modern humans from archaic hominins. They found that only 1.5 to 7 per cent of the modern human genome is unique to us.

The figure may seem low but that is partly because we inherited plenty of DNA from the ancient ancestral species that ultimately gave rise to modern humans and the Neanderthals and Denisovans.
What’s more, modern humans then interbred with Neanderthals and Denisovans, picking up even more DNA that isn’t unique to our lineage.
“It’s true that individual humans have a very low per cent of their genome that might have been from Neanderthal or Denisovan ancestry – non-Africans can have between 1.5 to 2.1 per cent of their genome that originated from Neanderthal ancestry,” says Schaefer.
But we know that the exact form taken by that small amount of Neanderthal DNA varies from individual to individual – meaning two people can both have 2 per cent Neanderthal DNA but share little Neanderthal DNA in common. These differences add up, says Shaefer. Some estimates suggest about 40 per cent of the Neanderthal genome can be pieced together by combining genetic information from a wide variety of living people.
The mutations that contribute to uniquely human features are contained within a small part of the genome and seem to mainly affect genes related to brain development.
“Knowing how those variants affect human mental capacities would help us understand the cognitive differences between humans and Neanderthals,” says Montgomery Slatkin at the University of California, Berkeley.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abc0776
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Many people strive to touch their toes or do the splits, but it is perfectly possible to get all the benefits of stretching without pushing your body to its limits

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14 July 2021

By Caroline Williams

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“I BEND so I don’t break.” No one knows who first coined this phrase, but search for it online and you will find it accompanying numerous pictures of yogis in various states of contortion. Flexibility, according to common wisdom, is not only impressive to look at, but something we should actively work towards.
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By Adam Rutherford

Michelle D’urbano
UNSHARED science is of little value. The whole scientific endeavour relies on ideas, methods and data being available to all. The words we use are vital to making sure that we are all on the same page and our ideas are conveyed accurately. But in my field of genetics, the language we use isn’t up to scratch. Terms in common usage present problems ranging from being scientifically confused or ambiguous, to being rooted in a racist history that echoes in our present.
Every scientific discipline has its own jargon used to summarise or label the complexity of the world. And as our genome is the richest data set we have ever tackled, it is no surprise that human genetics is particularly burdened with terms that strive to encapsulate our ancestry and the secrets of our behaviour, evolution and disease.
Genetics is also a field with a pernicious history. Its origins are inextricably entwined with the 18th-century invention of race, then using pigmentation and skull measurements to hierarchically taxonomise people. With that came scientific racism marshalled into the justification of slavery and subjugation, and the eugenics projects of the early 20th century followed not far behind.Advertisement
Contemporary genetics has unequivocally demolished the attempts to use ancestry, anatomy and genetics to assert a biological basis for race. Although people around the world differ, the genetics underlying those differences doesn’t correspond to the racial classification that we use today. “Black” – meaning people of recent African descent – covers more than a billion people with more genetic diversity than the rest of the world put together. From a genetic point of view, it isn’t an informative term. Yet we use it. This is why we call race a “social construct” – race exists because we perceive it, but has no meaningful biological basis.
Nevertheless, the scientific language of the past resounds today. That is why I and colleagues in various fields of genetics are calling for a change in these language conventions, which, we argue, don’t serve scientific insight and shackle us to the prejudices of history.
Some examples are widespread. Caucasian, for example, is a word used today in official forms, public discourse and in many academic papers. Does it mean white European? Does it include people from south Asia or North Africa? Different definitions have included these populations and others. Furthermore, it was originally coined to indicate the “beauty” and “superiority” of white Europeans. It has no place in science today.
Other examples are arguably less prejudicial, but equally unsound. Bantu is often used to broadly describe people from southern Africa with a shared linguistic heritage. Yet the diversity of dialects in more than 400 million people renders their grouping imprecise and not inherently meaningful. Even terms like “ethnicity” and “ancestry” have subtly different meanings when used in different fields and by different people.
In the genetics community, there is growing recognition that we have to change our language. The American Society of Human Genetics stated in 2018 that “the invocation of genetics to promote racist ideologies is one of many factors causing racism to persist”.
Humans are all of one species, but people from around the world are different, and genetics reflects those regional adaptations and different evolutionary journeys. Grouping people is a necessary part of understanding similarities and differences in our DNA.
Our intention isn’t to police language, but to prompt it to evolve. Some genetics terms should be consigned to the dustbin; others will require thought and discussion. Our hope is to spark a conversation for changing to a lexicon that better serves our understanding of human diversity, and simultaneously frees us from a troubling history.

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