Philippa Kaur
More stories
- in Humans
James Lovelock says artificial intelligence is the start of new life
In his new book Novacene, James Lovelock says the creation of AlphaGo was the start of a new kingdom of life that will create and think for itself. He’s optimistic that this new kingdom of life will want to keep us around like we keep plants in gardens. In our interview at his house near Chesil Beach we discuss the future of Gaia, our new AI overlords and why Elon Musk’s Mars mission is crazy. More
- in Humans
Lee Berger: Rewriting human history
Recent discoveries of fossils of ancient human relatives in southern Africa are disrupting our long-held ideas of the origins of humankind. Two of these discoveries, Australopithecus sediba and Homo naledi, represent significant contributions to this shakeup of our family tree. And there’s much more to come, as Berger explains in this interview with New Scientist […] More
- in Humans
Richard Dawkins: How we can outgrow God and religion
Richard Dawkins is one of the world’s most famous scientists, a best-selling author – and a hugely controversial figure. His works on evolutionary biology inspired millions, but his bestselling book The God Delusion started a new phase of his career as an outspoken critic of all things religious. We met him at his home in Oxford to find out more. More
The star cluster closest to Earth is in its death throes
The closest cluster of stars to Earth is falling apart and will soon die, astronomers say.
Using the Gaia spacecraft to measure velocities of stars in the Hyades cluster and those escaping from it, researchers have predicted the cluster’s demise. “We find that there’s only something like 30 million years left for the cluster to lose its mass completely,” says Semyeong Oh, an astronomer at the University of Cambridge.
“Compared to the Hyades’ age, that’s very short,” she says. The star cluster, just 150 light-years away and visible to the naked eye in the constellation Taurus, formed about 680 million years ago from a large cloud of gas and dust in the Milky Way.
Stellar gatherings such as the Hyades, known as open star clusters, are born with hundreds or thousands of stars that are held close to one another by their mutual gravitational pull. But numerous forces try to tear them apart: Supernova explosions from the most massive stars eject material that had been binding the cluster together; large clouds of gas pass near the cluster and yank stars out of it; the stars themselves interact with one another and jettison the least massive ones; and the gravitational pull of the whole Milky Way galaxy lures stars away too. As a result, open star clusters rarely reach their billionth birthday.Sign Up For the Latest from Science News
Headlines and summaries of the latest Science News articles, delivered to your inbox
The Hyades has survived longer than many of its peers. But astronomers first saw signs of trouble there in 2018, when teams in Germany and Austria independently used the European Space Agency’s Gaia space observatory to find numerous stars that had escaped the cluster. These departing stars form two long tails on opposite sides of the Hyades — the first ever seen near an open star cluster. Each stellar tail stretches hundreds of light-years and dwarfs the cluster itself, which is about 65 light-years across.
In the new work, posted July 6 at arXiv.org, Oh and Cambridge colleague N. Wyn Evans analyzed how the cluster has lost stars over its life. It was born with about 1,200 solar masses but now has only 300 solar masses left. In fact, the two tails of escapees possess more stars than does the cluster. And the more stars the cluster loses, the less gravity it has to hold on to its remaining members, which leads to the escape of additional stars, exacerbating the cluster’s predicament.Siegfried Röser, an astronomer at Heidelberg University in Germany who led one of the two teams that discovered the cluster’s tails, agrees that the Hyades is in its sunset years. But he worries that it’s too early to pin a precise date on the funeral. “That seems to be a little bit risky to say,” Röser says. Running a computer simulation with the stars’ masses, positions and velocities should better show what will happen in the future, he says.
The main culprit behind the cluster’s coming demise, Oh says, is the Milky Way. Just as the moon causes tides on Earth, lifting the seas on both the side facing the moon and the side facing away, so the galaxy exerts tides on the Hyades: The Milky Way pulls stars out of the side of the cluster that faces the galactic center as well as the cluster’s far side.
Even millions of years after the cluster disintegrates, its stars will continue to drift through space with similar positions and velocities, like parachutists jumping out of the same airplane. “It’s still probably going to be detectable as a coherent structure in position-velocity space,” Oh says, but the stars will be so spread out from one another that they will no longer constitute a star cluster. More- in Humans
How the slave trade left its mark in the DNA of people in the Americas
By Michael Marshall
The distribution of slavery in southern US states in 1860
Niday Picture Library / AlamyA study of the DNA of people in the Americas with African heritage has revealed overlooked details about the transatlantic slave trade.
“This gives some clarity and some sense of individual history,” says historian Linda Heywood of Boston University in Massachusetts, who wasn’t involved in the research. DNA evidence means African Americans can pinpoint where their ancestors were abducted from and reclaim aspects of their heritage that were hidden by the slave trade, she says. “It broadens the way in which identity and personal history can be thought about.”
An estimated 12.5 million people were taken from Africa to the Americas between the 1500s and 1800s, according to historical texts like shipping documents and records of people being sold.Advertisement
To fill out the picture, Steven Micheletti of consumer genetics firm 23andMe in Sunnyvale, California, and his colleagues looked at DNA from 50,281 people, including 27,422 people from across the Americas with a minimum of 5 per cent African ancestry, 20,942 Europeans and 1917 Africans. This allowed them to identify stretches of DNA that are unique to people from particular regions of Africa.
The data came from 23andMe customers, along with public genome databases. Studies like this are becoming possible because African people, who were previously under-represented in genome databases, are now being asked to take part in research, says Joanna Mountain, also of 23andMe. Nevertheless, gaps remain. “I’m hoping we get some data from Mozambique sometime soon. It was involved in the slave trade, but we didn’t have enough data to include it in this study,” she says.In line with historical records of where slaves were taken from, the African DNA in people in the Americas was most similar to that of people living in west African countries like Senegal, the Democratic Republic of the Congo and Angola.
However, most people in the Americas with African ancestry won’t have DNA from a single region of Africa. “Our results suggest the average African American would have connections to multiple regions,” says Micheletti. That is partly because slave traders disregarded ethnic identities, mixing people from different groups, and partly because African Americans moved around within the US. For instance, during the Great Migration of the 20th century African Americans moved from the segregated southern states of the US to northern states.
Because so many people were abducted as slaves, much of the genetic diversity in Africa was carried to the Americas, says Eduardo Tarazona-Santos at the Federal University of Minas Gerais in Belo Horizonte, Brazil. “But within the Americas, this diversity was more homogenised between populations.”The analysis points to overlooked details of the slave trade. For instance, the team found less DNA from Senegal, Gambia and regions in other neighbouring countries than would be expected given the huge numbers of people taken from there. This may be because those slaves were often taken to rice plantations in the US, where the death rate was high due to malaria, says the team.
Meanwhile, many people in Central and South America and on many Caribbean islands today carry little African DNA – despite the fact that 70 per cent of slaves who survived the trip to the Americas were sent there.
This may reflect a form of racism once practised in Brazil, says Mountain, in which women of African descent were raped or forced to marry Europeans to promote “racial whitening”. In contrast, in the US, African Americans were often segregated from white people by law, and racial intermarriage was illegal or taboo.
The genetic data also confirms that female slaves have passed on much more of their DNA than male slaves – even though historical records show the majority of people taken from Africa were male. This is probably because female slaves were subjected to rape and sexual exploitation.
Journal reference: American Journal of Human Genetics, DOI: 10.1016/j.ajhg.2020.06.012
More on these topics: More - in Humans
Caroline Criado-Perez: covid-19 and gender
Award-winning writer and campaigner Caroline Criado-Perez, speaks with New Scientist medical reporter Clare Wilson about how systematic gender biases are impacting women and men differently as the world copes with the coronavirus. For example, personal protective equipment is not only in short supply, its design – often based upon male body norms – is putting women at higher risk. Meanwhile, covid-19 affects men and women differently with men dying at a slightly higher rate, but many countries are not collecting sex-disaggregated data, making it difficult to understand the differences and mitigate some of the worst effects, she says. More
