Category Archives: Uncategorized

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.

Science for the People: Medical Marijuana

sftpThis week, Science for the People is taking a closer look at the medical marijuana controversy. How effective is medical marijuana and for what conditions is it a suitable treatment? In our attempt to separate evidence from anecdote we’re joined by a panel of three: Dr. David Casarett, a palliative care physician and author of the book Stoned: A Doctor’s Case for Medical Marijuana; Dr. Robert Wolff, a systematic reviewer for Kleijnen Systematic Reviews and coauthor of a recent systematic review to assess benefits and harms of cannabis for medical use; and Dr. Marcel Bonn-Miller, assistant professor in the Department of Psychiatry at the University of Pennsylvania Perelman School of Medicine, who has dedicated his career to understanding the relationship between cannabis use and PTSD.

Science for the People is now part of the Skepchick Network.

Don’t forget to support the Science for the People on Patreon to keep the sciencey goodness flowing toward your ear holes.

*Josh provides research help to Science for the People and is, therefore, completely biased.

Revisting the blink comparator and The Rural Alberta Advantage

Today is the anniversary of the discovery of our sentimental favourite dwarf planet, Pluto. On February 18, 1930 Clyde Tombaugh, working at the Lowell Observatory in Flagstaff, found the first evidence of a planet beyond Neptune. This seems like the perfect day to revisit an old post about a song that reminded me of the equipment he used. This is an edited and updated version of a Finch and Pea post from February 11, 2012.

With rich dark wooden curio cabinets and a narrow book-filled balcony accessed by a steep staircase, the Rotunda at the Lowell Observatory in Flagstaff feels like a natural home for the distinguished scientist. I visited the Lowell in 2011 for the National Association of Science Writers meeting, and it was everything that I had always imagined being a scientist would be when I was a kid. Feeling the warm glow of scientific discoveries past, there was one thing in the room I couldn’t take my eyes off: the glass plates and elegant brass eyepiece of the blink comparator used to discover Pluto. Continue reading

Art of Science: Chasing a Comet From Lab to Studio


Ekaterina Smirnova, 67P V, Watercolor on Paper, 2015

Some painters grind their own pigments, but Ekaterina Smirnova is the first artist I know of who makes her own water. Smirnova was inspired by the landing of the robotic probe Philae on comet 67P Churyumov–Gerasimenko in 2014. When she learned that scientists had discovered that the water on the comet is very different from the water on Earth, she decided to try to generate water that is similar in composition to the water found on 67P and use it in her paintings.

Smirnova found out that the water on 67P was heavy water, containing D20, or deuterium oxide. Since it’s not the kind of thing you can pick up at the grocery store, Smirnova set about McGyvering a system to make some in her studio, using electrolysis. (blog) That didn’t produce quite the results she wanted, so she bought some from a nuclear energy source and mixed until she was satisfied.

The artist says that through her work she studies the relationship between humans and the universe. She is particularly interested in the vapor that is released when the comet passes close to the Sun, forming the comet’s tail.

67p VII

67P VII, Watercolor on Paper, 2015

The focus on vapor and spray carries through to her painting technique: “I use splashing techniques, vaporizing watercolor paint before it hits the paper, this allows me to create an effect of mist, little droplets of water streaming with a strong force to the dark vacuum of space. Painting most of the work without touching paper with a brush, I use 30 to 40 layers, which helps to create complex textures on the painting.”

Next month, Smirnova will show her 67P-inspired work, including a musical collaboration to an audience of scientists at the 50th ESALAB Symposium which will be held in Leiden, in the Netherlands.  If you can’t make it there, she’ll be showing in New York later this year.