Ancient civilizations emitted greenhouse gasses, too; the red and orange dots above
mark indirect measures of methane in the atmosphere over the past two millennia.
Scientists have thought that humans only started emitting significant quantities of greenhouse gasses in the 19th century, after the Industrial Revolution—and the fossil fuels that powered it—took hold. But a study in Nature today suggests that our history as heavy emitters stretches back much farther, to the charcoal fires of the Roman Empire and the intensive agriculture of Han China.
To examine carbon emissions past, the research team analyzed more than 50 ice cores from Greenland, gauging levels of the greenhouse gas methane in Earth’s atmosphere going back to 100 B.C. They looked at specific carbon signatures in the methane to determine whether it came from burning coal and other materials—meaning humans might have been involved—or a natural biological process, then used mathematical models to further narrow down manmade emissions from naturally occurring ones. Human emissions, they found, were noticeable, though minuscule compared to post-industrial levels; only perhaps 10% human methane emissions over the past 2,000 years were produced before 1800. For a time when there were far fewer people around, however, that’s still a lot of methane to be sending off into the atmosphere.
A tree’s rings mark both its age and the local environmental conditions, which allows researchers to track historical changes in an ecosystem. But tree rings can also encode signals from beyond Earth: Ancient trees in the Northern Hemisphere have preserved a radioactive souvenir from a 1200-year-old burst of cosmic rays.
Using tree rings, researchers have collected 3,000 years worth of data on the presence of the radioactive carbon isotope carbon-14 in the atmosphere. When examining the ebb and flow of carbon-14 over time, Japanese researchers noticed an increase during the 8th and 9th centuries CE. They decided to look at that period in detail by studying the yearly concentrations of carbon-14 in Japanese cedar trees. The cedars revealed a 1.2 percent carbon-14 spike that lasted less than a year between 774 and 775 CE, which corresponded with similar spikes in North American and European trees. This peak, twenty times the amount of variation normally caused by the sun’s fluctuations, resulted from a short-term burst of cosmic rays. But where did those rays come from—a supernova, a solar flare, or some other source?
The Y chromosome, at the bottom right of this set of human
chromosomes, is dwarfed by the X.
Over the last few decades, scientists and journalists have speculated that the end of man—men, that is—was nigh. The biological reason for this possibility is the ever-shrinking Y chromosome: 300-200 million years ago, the Y, like females’ X chromosome, had hundreds of genes, but it now contains less than 80, 19 of which code for specifically male traits such as sperm production. This remarkable contraction set people’s imaginations spinning, especially after an opinion piece said in Nature 10 years ago that the Y chromosome might disappear, as it already has in voles, in 10 million years.
A Nature paper published this week, however, may indicate that the Y is sticking around. Biologists at the Whitehead Institute have compared the Y chromosome of rhesus monkeys with the human Y chromosome, and they’ve found that the two have the same number but one of key male-specific genes. This implies that the human Y chromosome’s shrinkage, at least when it comes to key genes, stopped at least around 25 million years ago, when the common ancestor of humans and rhesus monkeys was alive. The team says that this 25 million years of stasis indicates that the Y’s days of sloughing genes are over, that the genes it carries now are the essential ones and cannot be removed without seriously impacting reproductive function, while the genes lost in the past were expendable.
Neurons damaged by Parkinson’s disease
What’s the News: Scientists have reversed Parkinson’s disease-like brain damage and motor problems in mice and rats using neurons grown from human embryonic stem cells. The new technique, described online in Nature earlier this week, brings scientists closer to similar treatments for people with Parkinson’s.
What’s the News: Making stem cells without using embryos can be a difficult process, and scientists have had to cope with numerous failures. But a new discovery may help them home in on what’s missing from their biochemical recipes.
Those dark rings in the bottom of your cup arise from fundamental physics.
What’s the News: Some of the most mundane things in life—drinking through a straw, for instance, or washing your hands with soap—are the results of some really neat physics. Today, scientists are adding another item to that list: The ring that forms around a drying drop of coffee. A team at University of Pennsylvania has discovered that that brown ring is a result of the shape of the particles floating in your coffee—and if you squash them out a little, the coffee ring disappears.
What’s the News: Hemophilia is perhaps best known as a disease of nineteenth-century royalty (specifically, of the oft-intermarried Hapsburgs), but it has evaded our efforts at a cure for thousands of years. And its effects are gruesome: mutations in the gene for a crucial clotting factor mean that victims can rapidly bleed to death from even small cuts.
Now, researchers working with hemophiliac mice have demonstrated a simple and apparently safe technique to swap in a functioning gene, giving hope for a future respite for sufferers of the disease.
What’s the News: Adding sugar to certain antibiotics can boost their bacteria-battling ability, according to a study published today in Nature. In particular, sugar helps the drugs wipe out persisters, bacteria that evade antibiotics by essentially going dormant only to flare up again once the danger has passed. This technique could lead to the development of inexpensive, more effective treatments for bacterial infections.
What’s the News: As a European court looks poised to ban the patenting of technologies using human embryonic stem cells (hESCs), a group of prominent scientists has issued a warning: regenerative medicine is never going to leave the lab if no one can make money on it.
Queen bee larvae floating in royal jelly
What’s the News: It’s long been known that a female bee’s place in the social order—whether she becomes a worker or a queen—depends not on her genes, but on whether she eats royal jelly. A study published in Nature found that royalactin, a protein found in royal jelly, is responsible for many of the physical differences that distinguish queens from the hoi polloi of the hive—and, surprisingly, that royalactin can even cause fruit flies to develop queen bee-like traits. This finding also shines light on how, at a cellular level, royal jelly turns bees into queens.