Oct 12, 2017

New genetic findings help explain different skin colors in humans

Alessia Ranciaro, a senior research scientist at the University of Pennsylvania, collects a skin reflectance reading from a study participant from a Nilo-Saharan population. Photo: Tishkoff lab

Scientists have discovered new genetic variations in some African populations that influence skin color and suggest our earliest ancestors may have had a medium skin tone that later evolved to both darker and lighter tones seen in modern humans, per a five-year study published in Science Thursday.

Why this matters: Not only do the results alter the assumption that lighter skin evolved from the dark skin of ancestral humans, but they also help explain the vast range of skin color, identify possible patterns of human evolution and migration, and add to our understanding of human skin conditions like cancer and aging.

"To me, it has really changed some of the story about the evolution of skin color," Sarah Tishkoff, a geneticist at the University of Pennsylvania and leader of the international team, told Axios. Some of the variations in pigmentation genes appear to have originated roughly 1 million years ago, well before the emergence of modern humans, she said.

The study: The team used a color meter to read the level of melanin in the inner-arm skin of more than 2,000 people from Ethiopia, Tanzania and Botswana and sequenced genes from almost 1,600 of them. Later, a team confirmed their findings by testing the variations in zebrafish and mouse models.

The team found several novel variations (called alleles) in genes associated with pigmentation:

  • DDB1– repairs DNA damage done by ultraviolet light radiation and could be key to understanding melanoma.
  • SLC24A5 and OCA2 – these genes are implicated in albinism
  • HERC2 – regulates the OCA2 gene
  • MFSD12 – Study author Nicholas Crawford told Axios "I remember I was very excited" when we found this gene is associated with vitiligo (an autoimmune disease that creates patches of light-colored skin on dark-skinned people). Tishkoff said their study found MFSD12 also contributes to the production of a protein that plays a role in optimizing nutrition and fighting infection. "This may be key to figuring out how to manipulate skin pigmentation for therapeutic means," she said.

Migration implications: The data collected is consistent with there being an early migration event of modern humans out of Africa along the southern coast of Asia and into Australo-Melanesia, Tishkoff said.

Africa is key: "Many variances rose in Africa and some [of those] went to 100% frequency in Europe so it was only by going to Africa and looking at these variables" that they discovered some of these new genes, said Tishkoff, who calls herself a "major advocate" to increase all studies of genetics in Africa.

  • Rick Sturm, molecular geneticist at the University of Queensland who was not part of the study, agreed. "I had made a simple assumption that selection was happening on multiple genes in European populations as skin pigmentation was lightening, but I hadn't thought that similar process was happening in Africa for darkening."
  • Sturm said there is more research to be done: "The identified [genetic variations] still only explain about 28.9% of the variance seen in pigmentation, so other genes remain to be discovered."

Go deeper: Listen to Tishkoff talk about the study on this Science podcast (9:55).

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DOJ watchdog finds flaws in FBI surveillance process beyond Page application

Carter Page. Photo: Chip Somodevilla/Getty Images

The Justice Department inspector general found errors in 29 out of 29 randomized FBI applications for acquiring wiretap warrants through the Foreign Intelligence Surveillance Act, or FISA, according to a report released Tuesday.

Why it matters: The broad DOJ audit of the FISA program stems from a damning investigation into the FBI's surveillance of former Trump campaign aide Carter Page, which uncovered "serious performance failures" by some FBI officials during the Russia probe. The IG's final findings come as Congress debates whether to renew the authority it grants to the FISA courts.

Coronavirus dashboard

Illustration: Sarah Grillo/Axios

  1. Global: Total confirmed cases as of 3:30 p.m. ET: 838,061 — Total deaths: 41,261 — Total recoveries: 174,115.
  2. U.S.: Leads the world in confirmed cases. Total confirmed cases as of 3:30 p.m. ET: 177,452 — Total deaths: 3,440 — Total recoveries: 6,038.
  3. Public health updates: More than 400 long-term care facilities across the U.S. report patients with coronavirus — Older adults and people with other health conditions are more at risk, new data shows.
  4. Federal government latest: The White House and other institutions are observing several models to better understand and prepare cities for when the coronavirus is expected to peak in the U.S.
  5. In Congress: New York Rep. Max Rose deploys to National Guard to help coronavirus response.
  6. 🎧 Podcast: Misinformation in the coronavirus age.
  7. What should I do? Answers about the virus from Axios expertsWhat to know about social distancingQ&A: Minimizing your coronavirus risk.
  8. Other resources: CDC on how to avoid the virus, what to do if you get it.

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U.S. coronavirus updates: White House studies models projecting virus peak

Data: The Center for Systems Science and Engineering at Johns Hopkins; Map: Andrew Witherspoon/Axios

The White House and other institutions are observing several models to better understand and prepare cities for when the coronavirus is expected to peak in the U.S.

The state of play: The coronavirus is expected to peak in the U.S. in two weeks, but many states like Virginia and Maryland will see their individual peaks well after that, according to a model by the University of Washington's Institute for Health Metrics and Evaluation.

Go deeperArrowUpdated 3 hours ago - Health