The Legacy of Slavery in African American DNA

This week at Pacific Standard,  I discuss a recent study that examines the influence of slavery and its discriminatory aftermath in the genetic diversity in over 4,000 African American genomes. One of the most striking results of the study is probably the most obvious: On average, about 15% of the DNA of African Americans is of European origin – and, according the researchers’ best statistical model, that European DNA largely dates back to before the Civil War. That was a time when interracial sexual relations overwhelmingly took the form of whites raping black slaves. After the Civil War, according to the model, admixture between blacks and whites dropped off sharply.

Like I said, it’s not particularly surprising, but the breadth of the genetic legacy of slavery is striking.

The study makes some other intriguing suggestions about African American genetic history, especially regarding the enormous demographic shift of the Great Migration (~1915-1970), when 6 million African Americans left the South and settled in other parts of the country. The big takeaway from this study is that African American genetic history is one of coercion: coerced migration and coerced sex over a relatively short period of time, which left strong signals in the genetic diversity of present day African Americans.

Aside from the historical aspect, studies like this matter if African Americans are going to participate in the ongoing development of personalized genomic medicine. Because the genetic structure of the African American population differs from that of whites, African Americans have different genetic risk factors for disease – and even different risk variants for the same diseases. Studies like this lay the groundwork for an inclusive practice of genomic medicine.

Sunday Science Poem: Darwin and Happy Endings

Wisława Szymborska’s “Consolation” (2002)
henri_rousseau_-_fight_between_a_tiger_and_a_buffaloEvolution has always been more controversial socially than scientifically. After Darwin published the Origin, the idea that all species descended from common ancestors was quickly accepted by most biologists (though his proposed mechanism of evolution, natural selection, remained controversial until the 20th century). Socially, however, evolution was and remains difficult for many people to swallow. The literalist beliefs of religious fundamentalists of course conflict with evolution. But even among those who don’t have a particular religious axe to grind, discomfort is not uncommon. Evolution in practice is brutal: we posses our unique adaptations – our brains, our opposable thumbs, our ability to talk, to socialize, to feel, see, and touch – thanks to the selective death of billions of organism over eons.

In her hilarious poem “Consolation”, the late Nobel-winning Polish poet Wisława Szymborska ironically contrasts the brutality of the real world in which evolution plays out, with the romantic world we construct for ourselves. She portrays Darwin, the great thinker who first grasped the harsh reality of evolution, as someone who escapes by reading novels with only happy endings.

Supposedly for relaxation he read novels.
But he had a requirement:
they couldn't end sadly.
If he happened on one,
he flung it furiously in the fire.

True or not –
I gladly believe it.

Roaming in his mind over so many times and places
looking back on all the extinct species,
such triumphs of strong over weak,
so many tests of survival,
sooner or later all in vain,
that at least in fiction
and its micro-scale
he had a right to expect a happy ending.

And so necessarily: sunrays behind a cloud,
lovers together again, kin reconciled,
doubts dissolved, faith rewarded,
fortunes recovered, treasures dug up,
neighbors regret their mulishness,
good names restored, greed put to shame,
old maids married to respectable ministers,
schemers expelled to the other hemisphere,
forgers of documents cast down the stairs,
seducers of virgins hurrying to altars
orphans taken in, widows embraced,
pride humbled, wounds mended,
prodigal sons invited to the table,
the cup of bitterness poured into the sea,
tissues wet with tears of reconciliation,
universal singing and music-making,
and the puppy Fido,
lost already in the first chapter,
let him run home again
and bark joyfully.

Translation from the Polish by Michael A. White (2016)
Image: “Fight Between a Tiger and a Buffalo”, Henri Rousseau (1908), via Wikimedia Commons.

A visit to the Herschel Museum

(cross-posted from

The day after the Brexit referendum I went to visit a museum dedicated to two German immigrants, and some of England’s most prolific astronomers.

2016-06-24 13.50.02Siblings William and Caroline Herschel lived in Bath during the 18th century, in New King Street. Two and a half centuries later, the street was quiet, with recycling bags outside every door, and a few straggling hopeful “Vote Remain” posters in some of the windows. The Herschels used to live at number 19, where the front door was now partly open.

I stepped inside, into a very normal corridor of a very normal terraced house. Normal, aside from a man standing behind a desk in the room at the far end of the corridor, welcoming me to the museum, and explaining that I could walk around the house, which was entirely converted to a museum devoted to the Herschels’ life and work.

I started at the basement level, which had access to the garden. This was the very garden in which William Herschel discovered the planet Uranus in 1781.

Until his discovery, there were only six known planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter and Saturn. All of these could be seen with the naked eye, and had been recognized as planets from the way they travelled across the night sky and changed position in relation to the stars.

2016-06-24 13.47.23The remaining planets were too far away to see. There were telescopes at the time, but none were good enough to see that far into space with enough detail. William Herschel developed a telescope that made it possible to see further into space in more detail. He had a workshop attached to his home, where he worked on his telescopes, and he soon became the world’s foremost telescope maker.

But despite discovering a whole new planet, astronomy was just Herschel’s hobby at the time. His day job was as organist for the Octagon Chapel in Bath. The organ is no more, but a set of pipes from the old organ are on display in the music room, upstairs in the museum.

2016-06-24 13.57.50The music room also has several objects related to the life Caroline Herschel. She initially came to England to help her brother around the house and to pursue a professional singing career. When William’s astronomy hobby slowed turned into a full career, she became more involved with that, and made a few astronomical discoveries of her own.

When William discovered the planet Uranus, he proposed to name it Georgium Sidus (George’s Star) to honour England’s King George III, who was also Duke of Herschel’s hometown Hanover. The name didn’t stick, because other astronomers preferred a more international name, but in 1782, William Herschel was employed as King’s Astronomer. A few years later, the king also paid Caroline a salary for her assistance to William, making her the very first woman in the world to receive a salary for scientific work.

In the gift shop on the ground floor of the house I picked up two booklets about the Herschels’ musical careers, before heading back to the train station.


In the following days, it quickly became clear that in the wake of Brexit it has become quite difficult for European scientists in the UK, when nobody knows whether they will need visas, or whether new researchers will even want to come. Even British scientists are already having trouble applying for collaborative grants with their EU colleagues, as they might not qualify for the funding in a few years, and hinder the joint application.

So how did the Herschels get to work in England so easily, centuries before the EU? There may not have been a Europe-wide open borders scheme at the time, but there was an arrangement between Hanover and England, since they shared a ruler (King George III), so it was an obvious and easy choice to move between the two places.

I wanted to visit the museum because I was interested in the Herschels’ dual interests in music and science, but the date of my visit couldn’t have been more poignant, as the Herschel story is a textbook example of the work that foreign scientists have contributed to the UK.

Happy Mother’s Day to our backyard dinosaurs #finchstagram

Photo by Josh Witten (CC BY-NC-SA) via Instagram

Dear NSA, could you please check the metadata to confirm this sundial’s accuracy #finchstagram

Photo by Josh Witten (CC BY-NC-SA) via Instagram