Best foot forward

Scientists have described the 50,000-year-old toe bone found in a Siberian cave as a surprising view of the breeding habits of early humans in a “Lord of the Rings”-type world. Homo sapiens, Neanderthals and two other groups of early humans interbred before all species but ours became extinct, according to findings reported Wednesday in the journal Nature. A team of scientists sequenced the DNA from the Neanderthal toe fossil and compared it with the genomes of 25 present-day humans and to a sister group to Neanderthals called Denisovans. They found Neanderthals contributed about 2 percent of their DNA to modern people outside Africa and half a percent to Denisovans, who contributed 0.2 percent of their DNA to Asians and Native Americans. The biggest surprise was finding that a fourth hominin contributed 6 percent of the DNA in the Denisovan genome. This DNA donor’s identity remains a mystery.

Earth heat record

November set a heat record for Earth, scientists reported last week. It was the warmest November on record since record-keeping began in 1880. The National Oceanic and Atmospheric Administration says average global temperature, for water and land surfaces combined, was 56.6 degrees, 1.4 degrees above the 20th century average and the 37th consecutive November with above-average temps. Hottest were in Eurasia, Central America, the Indian Ocean and Russia.

New clues to HIV

Scientists say they have discovered a process by which the AIDS virus kills immune cells: It triggers a preprogrammed self-destruct sequence within the cell that is intended to alert other immune cells of a crisis. In papers published Thursday in both Science and Nature, researchers at the Gladstone Institutes and the University of California, San Francisco, wrote they not only discovered this process but also identified an existing drug that may halt it. Both studies focus on the body’s CD4 T cells, white blood cells that help defend against infection.

Global seed intrigue

Two scientists from China are charged with trying to steal seed samples from a company’s Kansas research facility. Weiqiang Zhang, 47, of Manhattan, Kan., and Wengui Yan, 63, of Stuttgart, Ark., are charged with conspiracy to steal trade secrets, the U.S. Attorney’s Office said. for Kansas said Dec. 12. Zhang worked as an agricultural seed breeder for the company since 2008, and Yan worked or the U.S. Department of Agriculture as a rice geneticist in Arkansas, the complaint says. They each face up to 10 years in prison and fines.

Ozone hole stabilizing

The hole in the ozone layer is stabilizing but will take until about 2070 to fully recover, according to new research by NASA scientists. The assessment comes more than two decades after the Montreal Protocol, the international treaty that banned chlorofluorocarbons and other compounds that deplete the ozone layer, which shields the planet from harmful ultraviolet rays. Levels of chlorine in the atmosphere are falling but have not yet dropped below the threshold necessary to have a shrinking effect on the ozone hole that forms each year over Antarctica, according to scientists at NASA’s Goddard Space Flight Center. They presented their findings last week at the annual meeting of the American Geophysical Union in San Francisco. That doesn’t mean the ozone hole is getting worse. But scientists who track its uneven progress say it is still too soon to declare a recovery. For now, year-to-year variations in temperature and winds, which each year carry ozone from the tropics to polar regions, are the driving factors in the size of the hole. In 2006, the ozone hole grew larger than ever. It reached a similar size in 2011 before shrinking in 2012 to its second-smallest size. Naturally occurring meteorological conditions were mostly responsible for those fluctuations, two NASA studies found.